/* -------------------------------------------------------------------------------

   Copyright (C) 1999-2007 id Software, Inc. and contributors.
   For a list of contributors, see the accompanying CONTRIBUTORS file.

   This file is part of GtkRadiant.

   GtkRadiant is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.

   GtkRadiant is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with GtkRadiant; if not, write to the Free Software
   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

   ----------------------------------------------------------------------------------

   This code has been altered significantly from its original form, to support
   several games based on the Quake III Arena engine, in the form of "Q3Map2."

   ------------------------------------------------------------------------------- */



/* dependencies */
#include "q3map2.h"



/*
   AllocDrawSurface()
   ydnar: gs mods: changed to force an explicit type when allocating
 */

static mapDrawSurface_t& AllocDrawSurface(){
	/* bounds check */
	if ( numMapDrawSurfs >= max_map_draw_surfs ) {
		Error( "max_map_draw_surfs (%d) exceeded, consider -maxmapdrawsurfs <N> to increase", max_map_draw_surfs );
	}
	return mapDrawSurfs[ numMapDrawSurfs++ ];
}

mapDrawSurface_t& AllocDrawSurface( ESurfaceType type, shaderInfo_t& si ){
	mapDrawSurface_t& ds = AllocDrawSurface();

	/* ydnar: do initial surface setup */
	new ( &ds ) mapDrawSurface_t{}; // placement new
	ds.type = type;
	ds.shaderInfo = &si;
	ds.fogNum = defaultFogNum;             /* ydnar 2003-02-12 */
	ds.surfaceNum = numMapDrawSurfs - 1;   /* ydnar 2003-02-16 */

	return ds;
}

mapDrawSurface_t& AllocDrawSurface( const mapDrawSurface_t& src ){
	mapDrawSurface_t& ds = AllocDrawSurface();

	/* ydnar: do initial surface setup */
	new ( &ds ) mapDrawSurface_t_params{ src }; // placement new
	ds.clearData(); // excess safety: must be already clean, if all kosher

	return ds;
}



/*
   ClearSurface() - ydnar
   clears a surface and frees any allocated memory
 */

void ClearSurface( mapDrawSurface_t& ds ){
	ds.type = ESurfaceType::Bad;
	ds.planar = false;
	ds.planeNum = -1;
	ds.clearData();
}



/*
   FinishSurface()
   ydnar: general surface finish pass
 */
static void MakeCelSurface( const mapDrawSurface_t& src, shaderInfo_t& si );

static void FinishSurface( mapDrawSurface_t& ds ){
	/* ydnar: rocking tek-fu celshading */
	if ( ds.celShader != nullptr ) {
		MakeCelSurface( ds, *ds.celShader );
	}

	/* backsides stop here */
	if ( ds.backSide ) {
		return;
	}

	/* ydnar: rocking surface cloning (fur baby yeah!) */
	if ( !strEmptyOrNull( ds.shaderInfo->cloneShader ) ) {
		CloneSurface( ds, ShaderInfoForShader( ds.shaderInfo->cloneShader ) );
	}

	/* ydnar: q3map_backShader support */
	if ( !strEmptyOrNull( ds.shaderInfo->backShader ) ) {
		mapDrawSurface_t& ds2 = CloneSurface( ds, ShaderInfoForShader( ds.shaderInfo->backShader ) );
		ds2.backSide = true;
	}
}



/*
   CloneSurface()
   clones a map drawsurface, using the specified shader
 */

mapDrawSurface_t& CloneSurface( const mapDrawSurface_t& src, shaderInfo_t& si ){
	/* allocate a new surface */
	mapDrawSurface_t& ds = AllocDrawSurface( src );

	/* copy it besides side references */
	ds.verts = src.verts;
	ds.indexes = src.indexes;

	/* set shader */
	ds.shaderInfo = &si;

	/* return the surface */
	return ds;
}



/*
   MakeCelSurface() - ydnar
   makes a copy of a surface, but specific to cel shading
 */

static void MakeCelSurface( const mapDrawSurface_t& src, shaderInfo_t& si ){
	/* don't create cel surfaces for certain types of shaders */
	if ( ( src.shaderInfo->compileFlags & C_TRANSLUCENT ) ||
	     ( src.shaderInfo->compileFlags & C_SKY ) ) {
		return;
	}

	/* make a copy */
	mapDrawSurface_t& ds = CloneSurface( src, si );

	/* do some fixups for celshading */
	ds.planar = false;
	ds.planeNum = -1;
	ds.celShader = nullptr; /* don't cel shade cels :P */
}



/*
   MakeSkyboxSurface() - ydnar
   generates a skybox surface, viewable from everywhere there is sky
 */

static void MakeSkyboxSurface( mapDrawSurface_t& src ){
	/* make a copy */
	mapDrawSurface_t& ds = CloneSurface( src, *src.shaderInfo );

	/* set parent */
	ds.parent = &src;

	/* scale the surface vertexes */
	for ( bspDrawVert_t& vert : ds.verts )
	{
		matrix4_transform_point( skyboxTransform, vert.xyz );

		/* debug code */
		//%	bspDrawVerts[ bspDrawSurfaces[ ds->outputNum ].firstVert + i ].color[ 0 ][ 1 ] = 0;
		//%	bspDrawVerts[ bspDrawSurfaces[ ds->outputNum ].firstVert + i ].color[ 0 ][ 2 ] = 0;
	}

	/* so backface culling creep doesn't bork the surface */
	ds.lightmapVecs[ 2 ].set( 0 );
}



/*
   TidyEntitySurfaces() - ydnar
   deletes all empty or bad surfaces from the surface list
 */

void TidyEntitySurfaces( const entity_t& e ){
	/* note it */
	Sys_FPrintf( SYS_VRB, "--- TidyEntitySurfaces ---\n" );

	/* walk the surface list */
	int deleted = 0;
	for ( int i = e.firstDrawSurf, end = std::exchange( numMapDrawSurfs, i ); i != end; ++i )
	{
		mapDrawSurface_t& ds = mapDrawSurfs[ i ];
		/* this surface ok? */
		if ( ( ds.type != ESurfaceType::Bad && !ds.verts.empty() )
		    || ds.type == ESurfaceType::Flare || ds.type == ESurfaceType::Shader ) {
			/* copy if necessary */
			if ( i != numMapDrawSurfs ) {
				mapDrawSurfs[ numMapDrawSurfs ] = std::move( ds );
			}
			++numMapDrawSurfs;
		}
		else{
			/* nuke it */
			ClearSurface( ds );
			deleted++;
		}
	}

	/* emit some stats */
	Sys_FPrintf( SYS_VRB, "%9d empty or malformed surfaces deleted\n", deleted );
}



static Vector2 CalcSurfaceTextureBias( const mapDrawSurface_t& ds ){
	/* walk the verts and determine min/max st values */
	Vector2 mins( 999999, 999999 ), maxs( -999999, -999999 ), bias;
	for ( const bspDrawVert_t& vert : ds.verts )
	{
		for ( int j = 0; j < 2; ++j )
		{
			value_minimize( mins[ j ], vert.st[ j ] );
			value_maximize( maxs[ j ], vert.st[ j ] );
		}
	}

	/* clamp to integer range and calculate surface bias values */
	for ( int i = 0; i < 2; ++i )
		bias[ i ] = floor( 0.5f * ( mins[ i ] + maxs[ i ] ) );

	return bias;
}



/*
   CalcLightmapAxis() - ydnar
   gives closed lightmap axis for a plane normal
 */

Vector3 CalcLightmapAxis( const Vector3& normal ){
	/* test */
	if ( normal == g_vector3_identity ) {
		return g_vector3_identity;
	}

	/* get absolute normal */
	const Vector3 absolute( std::fabs( normal[ 0 ] ),
	                        std::fabs( normal[ 1 ] ),
	                        std::fabs( normal[ 2 ] ) );

	/* test and return */
	if ( absolute[ 2 ] > absolute[ 0 ] - 0.0001f && absolute[ 2 ] > absolute[ 1 ] - 0.0001f ) {
		if ( normal[ 2 ] > 0 ) {
			return g_vector3_axis_z;
		}
		else{
			return -g_vector3_axis_z;
		}
	}
	else if ( absolute[ 0 ] > absolute[ 1 ] - 0.0001f && absolute[ 0 ] > absolute[ 2 ] - 0.0001f ) {
		if ( normal[ 0 ] > 0 ) {
			return g_vector3_axis_x;
		}
		else{
			return -g_vector3_axis_x;
		}
	}
	else
	{
		if ( normal[ 1 ] > 0 ) {
			return g_vector3_axis_y;
		}
		else{
			return -g_vector3_axis_y;
		}
	}
}



/*
   ClassifySurfaces() - ydnar
   fills out a bunch of info in the surfaces, including planar status, lightmap projection, and bounding box
 */

#define PLANAR_EPSILON  0.5f    //% 0.126f 0.25f

void ClassifySurface( mapDrawSurface_t& ds ){
	Plane3f plane;
	static const Vector3 axii[ 6 ] =
	{
		{  0,  0, -1 },
		{  0,  0,  1 },
		{ -1,  0,  0 },
		{  1,  0,  0 },
		{  0, -1,  0 },
		{  0,  1,  0 }
	};


	{
		/* ignore bogus (or flare) surfaces */
		if ( ds.type == ESurfaceType::Bad || ds.verts.empty() ) {
			return;
		}

		/* get shader */
		shaderInfo_t *si = ds.shaderInfo;

		/* -----------------------------------------------------------------
		   force meta if vertex count is too high or shader requires it
		   ----------------------------------------------------------------- */

		if ( ds.type != ESurfaceType::Patch && ds.type != ESurfaceType::Face ) {
			if ( ds.numVerts() > maxSurfaceVerts ) {
				ds.type = ESurfaceType::ForcedMeta;
			}
		}

		/* -----------------------------------------------------------------
		   plane and bounding box classification
		   ----------------------------------------------------------------- */

		/* set surface bounding box */
		ds.minmax.clear();
		for ( const bspDrawVert_t& vert : ds.verts )
			ds.minmax.extend( vert.xyz );

		/* try to get an existing plane */
		if ( ds.planeNum >= 0 ) {
			plane = mapplanes[ ds.planeNum ].plane;
		}

		/* construct one from the first vert with a valid normal */
		else
		{
			plane = { 0, 0, 0, 0 };
			for ( const bspDrawVert_t& vert : ds.verts )
			{
				if ( vert.normal != g_vector3_identity ) {
					plane.normal() = vert.normal;
					plane.dist() = vector3_dot( vert.xyz, plane.normal() );
					break;
				}
			}
		}

		/* test for bogus plane */
		if ( vector3_length( plane.normal() ) == 0 ) {
			ds.planar = false;
			ds.planeNum = -1;
		}
		else
		{
			/* determine if surface is planar */
			ds.planar = true;

			/* test each vert */
			for ( const bspDrawVert_t& vert : ds.verts )
			{
				/* point-plane test */
				if ( std::fabs( plane3_distance_to_point( plane, vert.xyz ) ) > PLANAR_EPSILON ) {
					//%	if( ds.planeNum >= 0 )
					//%	{
					//%		Sys_Warning( "Planar surface marked unplanar (%f > %f)\n", std::fabs( dist ), PLANAR_EPSILON );
					//%		ds.verts[ i ].color[ 0 ][ 0 ] = ds.verts[ i ].color[ 0 ][ 2 ] = 0;
					//%	}
					ds.planar = false;
					break;
				}
			}
		}

		/* find map plane if necessary */
		if ( ds.planar ) {
			if ( ds.planeNum < 0 ) {
				ds.planeNum = FindFloatPlane( plane, Span( &ds.verts[ 0 ].xyz, 1 ) );
			}
			ds.lightmapVecs[ 2 ] = plane.normal();
		}
		else
		{
			ds.planeNum = -1;
			ds.lightmapVecs[ 2 ].set( 0 );
			//% if( ds.type == ESurfaceType::Meta || ds.type == ESurfaceType::Face )
			//%		Sys_Warning( "Non-planar face (%d): %s\n", ds.planeNum, ds.shaderInfo->shader );
		}

		/* -----------------------------------------------------------------
		   lightmap bounds and axis projection
		   ----------------------------------------------------------------- */

		/* vertex lit surfaces don't need this information */
		if ( si->compileFlags & C_VERTEXLIT || ds.type == ESurfaceType::Triangles || noLightmaps ) {
			ds.lightmapAxis.set( 0 );
			//% ds.lightmapVecs[ 2 ].set( 0 );
			ds.sampleSize = 0;
			return;
		}

		/* the shader can specify an explicit lightmap axis */
		if ( si->lightmapAxis != g_vector3_identity ) {
			ds.lightmapAxis = si->lightmapAxis;
		}
		else if ( ds.type == ESurfaceType::ForcedMeta ) {
			ds.lightmapAxis.set( 0 );
		}
		else if ( ds.planar ) {
			ds.lightmapAxis = CalcLightmapAxis( plane.normal() );
		}
		else
		{
			/* find best lightmap axis */
			int bestAxis;
			for ( bestAxis = 0; bestAxis < 6; ++bestAxis )
			{
				if ( std::ranges::none_of( ds.verts, [&]( const bspDrawVert_t& vert ){
					//% Sys_Printf( "Comparing %1.3f %1.3f %1.3f to %1.3f %1.3f %1.3f\n",
					//%     vert.normal[ 0 ], vert.normal[ 1 ], vert.normal[ 2 ],
					//%     axii[ bestAxis ][ 0 ], axii[ bestAxis ][ 1 ], axii[ bestAxis ][ 2 ] );
					return vector3_dot( vert.normal, axii[ bestAxis ] ) < 0.25f; /* fixme: adjust this tolerance to taste */
				} ) ) {
					break;
				}
			}

			/* set axis if possible */
			if ( bestAxis < 6 ) {
				//% if( ds.type == ESurfaceType::Patch )
				//%     Sys_Printf( "Mapped axis %d onto patch\n", bestAxis );
				ds.lightmapAxis = axii[ bestAxis ];
			}

			/* debug code */
			//% if( ds.type == ESurfaceType::Patch )
			//%     Sys_Printf( "Failed to map axis %d onto patch\n", bestAxis );
		}

		/* calculate lightmap sample size */
		if ( ds.shaderInfo->lightmapSampleSize > 0 ) { /* shader value overrides every other */
			ds.sampleSize = ds.shaderInfo->lightmapSampleSize;
		}
		else if ( ds.sampleSize <= 0 ) { /* may contain the entity asigned value */
			ds.sampleSize = sampleSize; /* otherwise use global default */
		}
		if ( ds.lightmapScale > 0 ) { /* apply surface lightmap scaling factor */
			ds.sampleSize = ds.lightmapScale * ds.sampleSize;
			ds.lightmapScale = 0; /* applied */
		}

		ds.sampleSize = std::clamp( ds.sampleSize, std::max( minSampleSize, 1 ), 16384 ); /* powers of 2 are preferred */
	}
}



/*
   ClassifyEntitySurfaces() - ydnar
   classifies all surfaces in an entity
 */

void ClassifyEntitySurfaces( const entity_t& e ){
	/* note it */
	Sys_FPrintf( SYS_VRB, "--- ClassifyEntitySurfaces ---\n" );

	/* walk the surface list */ /* numMapDrawSurfs may grow in FinishSurface() */
	for ( int i = e.firstDrawSurf; i < numMapDrawSurfs; ++i )
	{
		FinishSurface( mapDrawSurfs[ i ] );
		ClassifySurface( mapDrawSurfs[ i ] );
	}

	/* tidy things up */
	TidyEntitySurfaces( e );
}



/*
   GetShaderIndexForPoint() - ydnar
   for shader-indexed surfaces (terrain), find a matching index from the indexmap
 */

static byte GetShaderIndexForPoint( const indexMap_t& im, const MinMax& eMinmax, const Vector3& point ){
	/* this code is really broken */
	#if 0
	/* legacy precision fudges for terrain */
	Vector3 mins, maxs;
	for ( int i = 0; i < 3; ++i )
	{
		mins[ i ] = floor( eMinmax.mins[ i ] + 0.1 );
		maxs[ i ] = floor( eMinmax.maxs[ i ] + 0.1 );
	}
	const Vector3 size = maxs - mins;

	/* find st (fixme: support more than just z-axis projection) */
	const float s = std::clamp( floor( point[ 0 ] + 0.1f - mins[ 0 ] ) / size[ 0 ], 0.0, 1.0 );
	const float t = std::clamp( floor( maxs[ 1 ] - point[ 1 ] + 0.1f ) / size[ 1 ], 0.0, 1.0 );

	/* make xy */
	const int x = ( im.w - 1 ) * s;
	const int y = ( im.h - 1 ) * t;
	#else
	/* get size */
	const Vector3 size = eMinmax.maxs - eMinmax.mins;

	/* calc st */
	const float s = ( point[ 0 ] - eMinmax.mins[ 0 ] ) / size[ 0 ];
	const float t = ( eMinmax.maxs[ 1 ] - point[ 1 ] ) / size[ 1 ];

	/* calc xy */
	const int x = std::clamp( int( s * im.w ), 0, im.w - 1 );
	const int y = std::clamp( int( t * im.h ), 0, im.h - 1 );
	#endif

	/* return index */
	return im.pixels[ y * im.w + x ];
}



/*
   GetIndexedShader() - ydnar
   for a given set of indexes and an indexmap, get a shader and set the vertex alpha in-place
   this combines a couple different functions from terrain.c
 */

static shaderInfo_t& GetIndexedShader( const shaderInfo_t& parent, const indexMap_t& im, int numPoints, byte *shaderIndexes ){
	/* early out if bad data */
	if ( numPoints <= 0 || shaderIndexes == nullptr ) {
		return ShaderInfoForShader( "default" );
	}

	/* determine min/max index */
	byte minShaderIndex = 255;
	byte maxShaderIndex = 0;
	for ( const byte index : Span( shaderIndexes, numPoints ) )
	{
		value_minimize( minShaderIndex, index );
		value_maximize( maxShaderIndex, index );
	}

	/* set alpha inline */
	for ( byte& index : Span( shaderIndexes, numPoints ) )
	{
		/* straight rip from terrain.c */
		if ( index < maxShaderIndex ) {
			index = 0;
		}
		else{
			index = 255;
		}
	}

	/* get the shader */
	shaderInfo_t& si = ShaderInfoForShader( ( minShaderIndex == maxShaderIndex )
	                          ? String64( "textures/", im.shader, '_', int( maxShaderIndex ) )
	                          : String64( "textures/", im.shader, '_', int( minShaderIndex ), "to", int( maxShaderIndex ) ) );

	/* inherit a few things from parent shader */
	if ( parent.globalTexture ) {
		si.globalTexture = true;
	}
	if ( parent.forceMeta ) {
		si.forceMeta = true;
	}
	if ( parent.nonplanar ) {
		si.nonplanar = true;
	}
	if ( si.shadeAngleDegrees == 0 ) {
		si.shadeAngleDegrees = parent.shadeAngleDegrees;
	}
	if ( parent.tcGen && !si.tcGen ) {
		/* set xy texture projection */
		si.tcGen = true;
		si.vecs[ 0 ] = parent.vecs[ 0 ];
		si.vecs[ 1 ] = parent.vecs[ 1 ];
	}
	if ( parent.lightmapAxis != g_vector3_identity && si.lightmapAxis == g_vector3_identity ) {
		/* set lightmap projection axis */
		si.lightmapAxis = parent.lightmapAxis;
	}

	/* return the shader */
	return si;
}




/*
   DrawSurfaceForSide()
   creates a ESurfaceType::Face drawsurface from a given brush side and winding
   stores references to given brush and side
 */

const double SNAP_FLOAT_TO_INT = 8.0;
const double SNAP_INT_TO_FLOAT = ( 1.0 / SNAP_FLOAT_TO_INT );

static mapDrawSurface_t& DrawSurfaceForShader( const char *shader );

mapDrawSurface_t *DrawSurfaceForSide( const entity_t& e, const brush_t& b, const side_t& s, const winding_t& w ){
	shaderInfo_t        *si, *parent;
	Vector3 texX, texY;
	float x, y;
	Vector3 vTranslated;
	byte shaderIndexes[ 256 ];
	float offsets[ 256 ];


	/* ydnar: don't make a drawsurf for culled sides */
	if ( s.culled ) {
		return nullptr;
	}

	/* range check */
	if ( w.size() > MAX_POINTS_ON_WINDING ) {
		Error( "DrawSurfaceForSide: w->numpoints = %zu (> %d)", w.size(), MAX_POINTS_ON_WINDING );
	}

	/* get shader */
	si = s.shaderInfo;

	/* ydnar: gs mods: check for indexed shader */
	const bool indexed = ( si->indexed && b.im != nullptr );
	if ( indexed ) {
		/* get shader indexes for each point */
		for ( size_t i = 0; i < w.size(); ++i )
		{
			shaderIndexes[ i ] = GetShaderIndexForPoint( *b.im, b.eMinmax, w[ i ] );
			offsets[ i ] = b.im->offsets[ shaderIndexes[ i ] ];
			//%	Sys_Printf( "%f ", offsets[ i ] );
		}

		/* get matching shader and set alpha */
		parent = si;
		si = &GetIndexedShader( *parent, *b.im, w.size(), shaderIndexes );
	}

	/* ydnar: sky hack/fix for GL_CLAMP borders on ati cards */
	if ( skyFixHack && !si->skyParmsImageBase.empty() ) {
		//%	Sys_FPrintf( SYS_VRB, "Enabling sky hack for shader %s using env %s\n", si->shader, si->skyParmsImageBase );
		for( const auto *suffix : { "_lf", "_rt", "_ft", "_bk", "_up", "_dn" } )
			DrawSurfaceForShader( String64( si->skyParmsImageBase, suffix ) );
	}

	/* ydnar: gs mods */
	mapDrawSurface_t& ds = AllocDrawSurface( ESurfaceType::Face, *si );
	ds.entityNum = b.entityNum;
	ds.castShadows = b.castShadows;
	ds.recvShadows = b.recvShadows;

	ds.planar = true;
	ds.planeNum = s.planenum;
	ds.lightmapVecs[ 2 ] = mapplanes[ s.planenum ].normal();

	ds.mapBrush = &b;
	ds.addSideRef( &s );
	ds.fogNum = FOG_INVALID;
	ds.sampleSize = b.lightmapSampleSize;
	ds.lightmapScale = b.lightmapScale;
	ds.ambientColor = b.ambientColor;
	ds.verts.resize( w.size(), c_bspDrawVert_t0 );

	/* compute s/t coordinates from brush primitive texture matrix (compute axis base) */
	ComputeAxisBase( mapplanes[ s.planenum ].normal(), texX, texY );

	/* create the vertexes */
	for ( size_t j = 0; j < w.size(); ++j )
	{
		/* get the drawvert */
		bspDrawVert_t& dv = ds.verts[ j ];

		/* copy xyz and do potential z offset */
		dv.xyz = w[ j ];
		if ( indexed ) {
			dv.xyz[ 2 ] += offsets[ j ];
		}

		/* round the xyz to a given precision and translate by origin */
		if( g_brushSnap )
			for ( size_t i = 0; i < 3; ++i )
				dv.xyz[ i ] = SNAP_INT_TO_FLOAT * floor( dv.xyz[ i ] * SNAP_FLOAT_TO_INT + 0.5 );
		vTranslated = dv.xyz + e.originbrush_origin;

		/* ydnar: tek-fu celshading support for flat shaded shit */
		if ( flat ) {
			dv.st = si->stFlat;
		}

		/* ydnar: gs mods: added support for explicit shader texcoord generation */
		else if ( si->tcGen ) {
			dv.st[ 0 ] = vector3_dot( si->vecs[ 0 ], vTranslated );
			dv.st[ 1 ] = vector3_dot( si->vecs[ 1 ], vTranslated );
		}

		/* brush primitive texturing */
		else if ( g_brushType == EBrushType::Bp ) {
			/* calculate texture s/t from brush primitive texture matrix */
			x = vector3_dot( vTranslated, texX );
			y = vector3_dot( vTranslated, texY );
			dv.st[ 0 ] = s.texMat[ 0 ][ 0 ] * x + s.texMat[ 0 ][ 1 ] * y + s.texMat[ 0 ][ 2 ];
			dv.st[ 1 ] = s.texMat[ 1 ][ 0 ] * x + s.texMat[ 1 ][ 1 ] * y + s.texMat[ 1 ][ 2 ];
		}

		/* old quake-style or valve 220 texturing */
		else {
			/* nearest-axial projection */
			dv.st[ 0 ] = s.vecs[ 0 ][ 3 ] + vector3_dot( s.vecs[ 0 ].vec3(), vTranslated );
			dv.st[ 1 ] = s.vecs[ 1 ][ 3 ] + vector3_dot( s.vecs[ 1 ].vec3(), vTranslated );
			dv.st[ 0 ] /= si->shaderWidth;
			dv.st[ 1 ] /= si->shaderHeight;
		}

		/* copy normal */
		dv.normal = mapplanes[ s.planenum ].normal();

		/* ydnar: set color */
		if( indexed )
			dv.color.fill( Color4b( 255, 255, 255, shaderIndexes[ j ] ) ); /* ydnar: gs mods: handle indexed shader blending */
		else
			dv.color.fill( Color4b( 255 ) );
	}

	/* set cel shader */
	ds.celShader = b.celShader;

	/* set shade angle */
	if ( b.shadeAngleDegrees > 0 ) {
		ds.shadeAngleDegrees = b.shadeAngleDegrees;
	}

	/* ydnar: gs mods: moved st biasing elsewhere */
	return &ds;
}



/*
   DrawSurfaceForMesh()
   moved here from patch.c
 */

mapDrawSurface_t& DrawSurfaceForMesh( const entity_t& e, parseMesh_t& p ){
	Plane3f plane;
	shaderInfo_t        *si, *parent;
	byte shaderIndexes[ MAX_EXPANDED_AXIS * MAX_EXPANDED_AXIS ];
	float offsets[ MAX_EXPANDED_AXIS * MAX_EXPANDED_AXIS ];


	/* get mesh and shader shader */
	mesh_t& mesh = p.mesh;
	si = p.shaderInfo;

	/* get vertex count */
	const int numVerts = mesh.numVerts();

	/* to make valid normals for patches with degenerate edges,
	   we need to make a copy of the mesh and put the aproximating
	   points onto the curve */

	/* create a copy of the mesh */
	mesh_t copy( mesh );

	/* store off the original (potentially bad) normals */
	MakeMeshNormals( copy );
	for ( int i = 0; i < numVerts; ++i )
		mesh.verts()[ i ].normal = copy.verts()[ i ].normal;

	/* put the mesh on the curve */
	PutMeshOnCurve( copy );

	/* find new normals (to take into account degenerate/flipped edges */
	MakeMeshNormals( copy );
	for ( int i = 0; i < numVerts; ++i )
	{
		/* ydnar: only copy normals that are significantly different from the originals */
		if ( vector3_dot( copy.verts()[ i ].normal, mesh.verts()[ i ].normal ) < 0.75f ) {
			mesh.verts()[ i ].normal = copy.verts()[ i ].normal;
		}
	}

	/* ydnar: gs mods: check for indexed shader */
	const bool indexed = ( si->indexed && p.im != nullptr );
	if ( indexed ) {
		/* get shader indexes for each point */
		for ( int i = 0; i < numVerts; ++i )
		{
			shaderIndexes[ i ] = GetShaderIndexForPoint( *p.im, p.eMinmax, mesh.verts()[ i ].xyz );
			offsets[ i ] = p.im->offsets[ shaderIndexes[ i ] ];
		}

		/* get matching shader and set alpha */
		parent = si;
		si = &GetIndexedShader( *parent, *p.im, numVerts, shaderIndexes );
	}


	/* ydnar: gs mods */
	mapDrawSurface_t& ds = AllocDrawSurface( ESurfaceType::Patch, *si );
	ds.entityNum     = p.entityNum;
	ds.castShadows   = p.castShadows;
	ds.recvShadows   = p.recvShadows;

	ds.sampleSize    = p.lightmapSampleSize;
	ds.lightmapScale = p.lightmapScale;   /* ydnar */
	ds.ambientColor  = p.ambientColor;
	ds.patchWidth  = mesh.width;
	ds.patchHeight = mesh.height;
	ds.verts.assign( mesh.begin(), mesh.end() );

	ds.fogNum = FOG_INVALID;
	ds.planeNum = -1;

	ds.longestCurve  = p.longestCurve;
	ds.maxIterations = p.maxIterations;

	/* construct a plane from the first vert */
	plane.normal() = mesh.verts()[ 0 ].normal;
	plane.dist() = vector3_dot( mesh.verts()[ 0 ].xyz, plane.normal() );

	/* spew forth errors */
	if ( vector3_length( plane.normal() ) < 0.001f ) {
		Sys_Printf( "DrawSurfaceForMesh: bogus plane\n" );
	}

	/* test each vert */
	const bool planar = std::ranges::none_of( mesh, [&plane]( const bspDrawVert_t& vert ){
			/* normal test */
		return !VectorCompare( plane.normal(), vert.normal )
			/* point-plane test */
			|| std::fabs( plane3_distance_to_point( plane, vert.xyz ) ) > EQUAL_EPSILON;
	} );

	/* add a map plane */
	if ( planar ) {
		/* make a map plane */
		ds.planeNum = FindFloatPlane( plane, Span( &mesh.verts()[ 0 ].xyz, 1 ) );
		ds.lightmapVecs[ 2 ] = plane.normal();

		/* push this normal to all verts (ydnar 2003-02-14: bad idea, small patches get screwed up) */
		for ( bspDrawVert_t& vert : ds.verts )
			vert.normal = plane.normal();
	}

	/* walk the verts to do special stuff */
	for ( int i = 0; i < numVerts; ++i )
	{
		/* get the drawvert */
		bspDrawVert_t& dv = ds.verts[ i ];

		/* ydnar: tek-fu celshading support for flat shaded shit */
		if ( flat ) {
			dv.st = si->stFlat;
		}

		/* ydnar: gs mods: added support for explicit shader texcoord generation */
		else if ( si->tcGen ) {
			/* translate by origin and project the texture */
			const Vector3 vTranslated = dv.xyz + e.origin;
			dv.st[ 0 ] = vector3_dot( si->vecs[ 0 ], vTranslated );
			dv.st[ 1 ] = vector3_dot( si->vecs[ 1 ], vTranslated );
		}

		/* ydnar: set color */
		if( indexed )
			dv.color.fill( Color4b( 255, 255, 255, shaderIndexes[ i ] ) ); /* ydnar: gs mods: handle indexed shader blending */
		else
			dv.color.fill( Color4b( 255 ) );

		/* ydnar: offset */
		if ( indexed ) {
			dv.xyz[ 2 ] += offsets[ i ];
		}
	}

	/* set cel shader */
	ds.celShader = p.celShader;

	/* return the drawsurface */
	return ds;
}



/*
   DrawSurfaceForFlare() - ydnar
   creates a flare draw surface
 */

mapDrawSurface_t *DrawSurfaceForFlare( int entNum, const Vector3& origin, const Vector3& normal, const Vector3& color, const char *flareShader, int lightStyle ){
	/* emit flares? */
	if ( !emitFlares ) {
		return nullptr;
	}

	/* allocate drawsurface */
	mapDrawSurface_t& ds = AllocDrawSurface( ESurfaceType::Flare, ShaderInfoForShader( !strEmptyOrNull( flareShader )? flareShader : g_game->flareShader ) );

	/* set it up */
	ds.entityNum = entNum;
	ds.lightmapOrigin = origin;
	ds.lightmapVecs[ 2 ] = normal;
	ds.lightmapVecs[ 0 ] = color;

	/* store light style */
	ds.lightStyle = style_is_valid( lightStyle )? lightStyle : LS_NORMAL;

	/* fixme: fog */

	/* return to sender */
	return &ds;
}



/*
   DrawSurfaceForShader() - ydnar
   creates a bogus surface to forcing the game to load a shader
 */

static mapDrawSurface_t& DrawSurfaceForShader( const char *shader ){
	/* get shader */
	shaderInfo_t& si = ShaderInfoForShader( shader );

	/* find existing surface */
	for ( mapDrawSurface_t& ds : Span( mapDrawSurfs, numMapDrawSurfs ) )
		if ( ds.shaderInfo == &si )
			return ds;

	/* create a new surface */
	return AllocDrawSurface( ESurfaceType::Shader, si );
}



/*
   AddSurfaceFlare() - ydnar
   creates flares (coronas) centered on surfaces
 */

static void AddSurfaceFlare( mapDrawSurface_t& ds, const Vector3& entityOrigin ){
	Vector3 origin( 0 );
	/* find centroid */
	for ( const bspDrawVert_t& vert : ds.verts )
		origin += vert.xyz;
	origin /= ds.verts.size();
	origin += entityOrigin;

	/* push origin off surface a bit */
	origin += ds.lightmapVecs[ 2 ] * 2;

	/* create the drawsurface */
	DrawSurfaceForFlare( ds.entityNum, origin, ds.lightmapVecs[ 2 ], ds.shaderInfo->color, ds.shaderInfo->flareShader, ds.shaderInfo->lightStyle );
}



/*
   SubdivideFace()
   subdivides a face surface until it is smaller than the specified size (subdivisions)
 */

static void SubdivideFace_r( const entity_t& e, const brush_t& brush, const side_t& side, winding_t& w, int fogNum, float subdivisions ){
	int axis;
	MinMax bounds;
	const float epsilon = 0.1;
	int subFloor, subCeil;

	/* dummy check */
	if ( w.empty() ) {
		return;
	}
	if ( w.size() < 3 ) {
		Error( "SubdivideFace_r: Bad w->numpoints (%zu < 3)", w.size() );
	}

	/* determine surface bounds */
	WindingExtendBounds( w, bounds );

	/* split the face */
	for ( axis = 0; axis < 3; ++axis )
	{
		Vector3 planePoint( 0 );
		Plane3f plane( 0, 0, 0, 0 );


		/* create an axial clipping plane */
		subFloor = floor( bounds.mins[ axis ] / subdivisions ) * subdivisions;
		subCeil = ceil( bounds.maxs[ axis ] / subdivisions ) * subdivisions;
		planePoint[ axis ] = subFloor + subdivisions;
		plane.normal()[ axis ] = -1;
		plane.dist() = vector3_dot( planePoint, plane.normal() );

		/* subdivide if necessary */
		if ( ( subCeil - subFloor ) > subdivisions ) {
			/* clip the winding */
			auto [frontWinding, backWinding] = ClipWindingEpsilon( w, plane, epsilon ); /* not strict; we assume we always keep a winding */

			/* the clip may not produce two polygons if it was epsilon close */
			if ( frontWinding.empty() ) {
				w.swap( backWinding );
			}
			else if ( backWinding.empty() ) {
				w.swap( frontWinding );
			}
			else
			{
				SubdivideFace_r( e, brush, side, frontWinding, fogNum, subdivisions );
				SubdivideFace_r( e, brush, side, backWinding, fogNum, subdivisions );
				return;
			}
		}
	}

	/* create a face surface */
	mapDrawSurface_t *ds = DrawSurfaceForSide( e, brush, side, w );

	/* set correct fog num */
	ds->fogNum = fogNum;
}



/*
   SubdivideFaceSurfaces()
   chop up brush face surfaces that have subdivision attributes
   ydnar: and subdivide surfaces that exceed specified texture coordinate range
 */

void SubdivideFaceSurfaces( const entity_t& e ){
	/* note it */
	Sys_FPrintf( SYS_VRB, "--- SubdivideFaceSurfaces ---\n" );

	/* walk the list of original surfaces, numMapDrawSurfs may increase in the process */
	for ( mapDrawSurface_t& ds : Span( mapDrawSurfs + e.firstDrawSurf, mapDrawSurfs + numMapDrawSurfs ) )
	{
		/* only subdivide brush sides */
		if ( ds.type != ESurfaceType::Face || ds.mapBrush == nullptr || ds.sideRefs.empty() ) {
			continue;
		}

		/* get bits */
		const brush_t *brush = ds.mapBrush;
		const side_t& side = *ds.sideRefs.front();

		/* check subdivision for shader */
		const shaderInfo_t *si = side.shaderInfo;
		if ( si == nullptr ) {
			continue;
		}

		/* ydnar: don't subdivide sky surfaces */
		if ( si->compileFlags & C_SKY ) {
			continue;
		}

		/* get subdivisions from shader */
		const float subdivisions = si->subdivisions;
		if ( subdivisions < 1 ) {
			continue;
		}

		/* preserve fog num */
		const int fogNum = ds.fogNum;

		/* make a winding and free the surface */
		winding_t w = WindingFromDrawSurf( ds );
		ClearSurface( ds );

		/* subdivide it */
		SubdivideFace_r( e, *brush, side, w, fogNum, subdivisions );
	}
}



/*
   ====================
   ClipSideIntoTree_r

   Adds non-opaque leaf fragments to the convex hull
   ====================
 */

static void ClipSideIntoTree_r( const winding_t& w, side_t& side, const node_t *node ){
	if ( w.empty() ) {
		return;
	}

	if ( node->planenum != PLANENUM_LEAF ) {
		if ( side.planenum == node->planenum ) {
			ClipSideIntoTree_r( w, side, node->children[eFront] );
			return;
		}
		if ( side.planenum == ( node->planenum ^ 1 ) ) {
			ClipSideIntoTree_r( w, side, node->children[eBack] );
			return;
		}

		const Plane3f& plane = mapplanes[ node->planenum ].plane;
		auto [front, back] = ClipWindingEpsilonStrict( w, plane, ON_EPSILON ); /* strict, we handle the "winding disappeared" case */
		if ( front.empty() && back.empty() ) {
			/* in doubt, register it in both nodes */
			ClipSideIntoTree_r( w, side, node->children[eFront] );
			ClipSideIntoTree_r( w, side, node->children[eBack] );
		}
		else{
			ClipSideIntoTree_r( front, side, node->children[eFront] );
			ClipSideIntoTree_r( back, side, node->children[eBack] );
		}

		return;
	}

	// if opaque leaf, don't add
	if ( !node->opaque ) {
		AddWindingToConvexHull( w, side.visibleHull, mapplanes[ side.planenum ].normal() );
	}
}





static int g_numHiddenFaces, g_numCoinFaces;



#define CULL_EPSILON 0.1f

/*
   SideInBrush() - ydnar
   determines if a brushside lies inside another brush
 */

static bool SideInBrush( side_t& side, const brush_t& b ){
	/* ignore sides w/o windings or shaders */
	if ( side.winding.empty() || side.shaderInfo == nullptr ) {
		return true;
	}

	/* ignore culled sides and translucent brushes */
	if ( side.culled || ( b.compileFlags & C_TRANSLUCENT ) ) {
		return false;
	}

	/* side iterator */
	for ( const side_t& bside : b.sides )
	{
		/* fail if any sides are caulk */
		if ( bside.compileFlags & C_NODRAW ) {
			return false;
		}

		/* check if side's winding is on or behind the plane */
		const Plane3f& plane = mapplanes[ bside.planenum ].plane;
		const EPlaneSide s = WindingOnPlaneSide( side.winding, plane );
		if ( s == eSideFront || s == eSideCross ) {
			return false;
		}
		if( s == eSideOn && bside.culled && vector3_dot( mapplanes[ side.planenum ].normal(), plane.normal() ) > 0 ) /* don't cull by freshly culled with matching plane */
			return false;
	}

	/* don't cull autosprite or polygonoffset surfaces */
	if ( side.shaderInfo->autosprite || side.shaderInfo->polygonOffset ) {
		return false;
	}

	/* inside */
	side.culled = true;
	g_numHiddenFaces++;
	return true;
}


/*
   CullSides() - ydnar
   culls obscured or buried brushsides from the map
 */

static void CullSides( entity_t& e ){
	int k, l, first, second, dir;


	/* note it */
	Sys_FPrintf( SYS_VRB, "--- CullSides ---\n" );

	g_numHiddenFaces = 0;
	g_numCoinFaces = 0;

	/* brush interator 1 */
	for ( brushlist_t::iterator b1 = e.brushes.begin(); b1 != e.brushes.end(); ++b1 )
	{
		/* sides check */
		if ( b1->sides.empty() ) {
			continue;
		}

		/* brush iterator 2 */
		for ( brushlist_t::iterator b2 = std::next( b1 ); b2 != e.brushes.end(); ++b2 )
		{
			/* sides check */
			if ( b2->sides.empty() ) {
				continue;
			}

			/* original check */
			if ( b1->original == b2->original && b1->original != nullptr ) {
				continue;
			}

			/* bbox check */
			if ( !b1->minmax.test( b2->minmax ) ) {
				continue;
			}

			/* cull inside sides */
			for ( side_t& side : b1->sides )
				SideInBrush( side, *b2 );
			for ( side_t& side : b2->sides )
				SideInBrush( side, *b1 );

			/* side iterator 1 */
			for ( side_t& side1 : b1->sides )
			{
				/* winding check */
				winding_t& w1 = side1.winding;
				if ( w1.empty() ) {
					continue;
				}
				const int numPoints = w1.size();
				if ( side1.shaderInfo == nullptr ) {
					continue;
				}

				/* side iterator 2 */
				for ( side_t& side2 : b2->sides )
				{
					/* winding check */
					winding_t& w2 = side2.winding;
					if ( w2.empty() ) {
						continue;
					}
					if ( side2.shaderInfo == nullptr ) {
						continue;
					}
					if ( w1.size() != w2.size() ) {
						continue;
					}
					if ( side1.culled && side2.culled ) {
						continue;
					}

					/* compare planes */
					if ( ( side1.planenum & ~0x00000001 ) != ( side2.planenum & ~0x00000001 ) ) {
						continue;
					}

					/* get autosprite and polygonoffset status */
					if ( side1.shaderInfo->autosprite || side1.shaderInfo->polygonOffset ) {
						continue;
					}
					if ( side2.shaderInfo->autosprite || side2.shaderInfo->polygonOffset ) {
						continue;
					}

					/* find first common point */
					first = -1;
					for ( k = 0; k < numPoints; ++k )
					{
						if ( VectorCompare( w1[ 0 ], w2[ k ] ) ) {
							first = k;
							break;
						}
					}
					if ( first == -1 ) {
						continue;
					}

					/* find second common point (regardless of winding order) */
					second = ( ( first + 1 ) < numPoints )? ( first + 1 ) : 0;
					dir = 0;
					if ( vector3_equal_epsilon( w1[ 1 ], w2[ second ], CULL_EPSILON ) ) {
						dir = 1;
					}
					else
					{
						if ( first > 0 ) {
							second = first - 1;
						}
						else{
							second = numPoints - 1;
						}
						if ( vector3_equal_epsilon( w1[ 1 ], w2[ second ], CULL_EPSILON ) ) {
							dir = -1;
						}
					}
					if ( dir == 0 ) {
						continue;
					}

					/* compare the rest of the points */
					l = first;
					for ( k = 0; k < numPoints; ++k )
					{
						if ( !vector3_equal_epsilon( w1[ k ], w2[ l ], CULL_EPSILON ) ) {
							k = 100000;
						}

						l += dir;
						if ( l < 0 ) {
							l = numPoints - 1;
						}
						else if ( l >= numPoints ) {
							l = 0;
						}
					}
					if ( k >= 100000 ) {
						continue;
					}

					/* cull face 1 */
					if ( !side2.culled && !( side2.compileFlags & C_TRANSLUCENT ) && !( side2.compileFlags & C_NODRAW ) ) {
						side1.culled = true;
						g_numCoinFaces++;
					}

					if ( side1.planenum == side2.planenum && side1.culled ) {
						continue;
					}

					/* cull face 2 */
					if ( !side1.culled && !( side1.compileFlags & C_TRANSLUCENT ) && !( side1.compileFlags & C_NODRAW ) ) {
						side2.culled = true;
						g_numCoinFaces++;
					}

					// TODO ? this culls only one of face-to-face windings; SideInBrush culls both tho; is this needed at all or should be improved?
				}
			}
		}
	}

	/* emit some stats */
	Sys_FPrintf( SYS_VRB, "%9d hidden faces culled\n", g_numHiddenFaces );
	Sys_FPrintf( SYS_VRB, "%9d coincident faces culled\n", g_numCoinFaces );
}




/*
   ClipSidesIntoTree()

   creates side->visibleHull for all visible sides

   the drawsurf for a side will consist of the convex hull of
   all points in non-opaque clusters, which allows overlaps
   to be trimmed off automatically.
 */

void ClipSidesIntoTree( entity_t& e, const tree_t& tree ){
	/* ydnar: cull brush sides */
	CullSides( e );

	/* note it */
	Sys_FPrintf( SYS_VRB, "--- ClipSidesIntoTree ---\n" );

	/* walk the brush list */
	for ( brush_t& b : e.brushes )
	{
		/* walk the brush sides */
		for ( side_t& side : b.sides )
		{
			if ( side.winding.empty() ) {
				continue;
			}

			side.visibleHull.clear();
			ClipSideIntoTree_r( side.winding, side, tree.headnode );

			/* anything left? */
			if ( side.visibleHull.empty() ) {
				continue;
			}

			/* shader? */
			const shaderInfo_t *si = side.shaderInfo;
			if ( si == nullptr ) {
				continue;
			}

			/* don't create faces for non-visible sides */
			/* ydnar: except indexed shaders, like common/terrain and nodraw fog surfaces */
			if ( ( si->compileFlags & C_NODRAW ) && !si->indexed && !( si->compileFlags & C_FOG ) ) {
				continue;
			}

			/* always use the original winding for autosprites and noclip faces */
			const winding_t& w = ( si->autosprite || si->noClip )? side.winding : side.visibleHull;

			/* save this winding as a visible surface */
			DrawSurfaceForSide( e, b, side, w );

			/* make a back side for fog */
			if ( si->compileFlags & C_FOG ) {
				/* duplicate the up-facing side */
				side_t& newSide = *new side_t( side );
				newSide.visibleHull = ReverseWinding( w );
				newSide.planenum ^= 1;

				/* save this winding as a visible surface */
				DrawSurfaceForSide( e, b, newSide, newSide.visibleHull ); // references new side by sideref, leak!
			}
		}
	}
}



/*

   this section deals with filtering drawsurfaces into the bsp tree,
   adding references to each leaf a surface touches

 */

/*
   AddReferenceToLeaf() - ydnar
   adds a reference to surface ds in the bsp leaf node
 */

static int AddReferenceToLeaf( mapDrawSurface_t& ds, node_t *node ){
	/* dummy check */
	if ( node->planenum != PLANENUM_LEAF || node->opaque ) {
		return 0;
	}

	const int numBSPDrawSurfaces = bspDrawSurfaces.size();

	/* try to find an existing reference */
	if( std::ranges::find( node->drawSurfReferences, numBSPDrawSurfaces ) != node->drawSurfReferences.cend() )
		return 0;

	/* add a new reference */
	node->drawSurfReferences.push_back( numBSPDrawSurfaces );

	/* ydnar: sky/skybox surfaces */
	if ( node->skybox ) {
		ds.skybox = true;
	}
	if ( ds.shaderInfo->compileFlags & C_SKY ) {
		node->sky = true;
	}

	/* return */
	return 1;
}



/*
   AddReferenceToTree_r() - ydnar
   adds a reference to the specified drawsurface to every leaf in the tree
 */

static int AddReferenceToTree_r( mapDrawSurface_t& ds, node_t *node, bool skybox ){
	/* dummy check */
	if ( node == nullptr ) {
		return 0;
	}

	/* is this a decision node? */
	if ( node->planenum != PLANENUM_LEAF ) {
		/* add to child nodes and return */
		int refs = 0;
		refs += AddReferenceToTree_r( ds, node->children[ 0 ], skybox );
		refs += AddReferenceToTree_r( ds, node->children[ 1 ], skybox );
		return refs;
	}

	/* ydnar */
	if ( skybox ) {
		/* skybox surfaces only get added to sky leaves */
		if ( !node->sky ) {
			return 0;
		}

		/* increase the leaf bounds */
		for ( const bspDrawVert_t& vert : ds.verts )
			node->minmax.extend( vert.xyz );
	}

	/* add a reference */
	return AddReferenceToLeaf( ds, node );
}



/*
   FilterPointIntoTree_r() - ydnar
   filters a single point from a surface into the tree
 */

static int FilterPointIntoTree_r( const Vector3& point, mapDrawSurface_t& ds, node_t *node ){
	/* is this a decision node? */
	if ( node->planenum != PLANENUM_LEAF ) {
		/* classify the point in relation to the plane */
		const float d = plane3_distance_to_point( mapplanes[ node->planenum ].plane, point );

		/* filter by this plane */
		int refs = 0;
		if ( d >= -ON_EPSILON ) {
			refs += FilterPointIntoTree_r( point, ds, node->children[eFront] );
		}
		if ( d <= ON_EPSILON ) {
			refs += FilterPointIntoTree_r( point, ds, node->children[eBack] );
		}

		/* return */
		return refs;
	}

	/* add a reference */
	return AddReferenceToLeaf( ds, node );
}

/*
   FilterPointConvexHullIntoTree_r() - ydnar
   filters the convex hull of multiple points from a surface into the tree
 */

static int FilterPointConvexHullIntoTree_r( const std::array<Vector3, 16>& points, mapDrawSurface_t& ds, node_t *node ){
	/* is this a decision node? */
	if ( node->planenum != PLANENUM_LEAF ) {
		/* classify the point in relation to the plane */
		const Plane3f& plane = mapplanes[ node->planenum ].plane;

		float dmin = std::numeric_limits<float>::max(), dmax = std::numeric_limits<float>::lowest();
		for ( const Vector3& point : points )
		{
			const float d = plane3_distance_to_point( plane, point );
			value_maximize( dmax, d );
			value_minimize( dmin, d );
		}

		/* filter by this plane */
		int refs = 0;
		if ( dmax >= -ON_EPSILON ) {
			refs += FilterPointConvexHullIntoTree_r( points, ds, node->children[eFront] );
		}
		if ( dmin <= ON_EPSILON ) {
			refs += FilterPointConvexHullIntoTree_r( points, ds, node->children[eBack] );
		}

		/* return */
		return refs;
	}

	/* add a reference */
	return AddReferenceToLeaf( ds, node );
}


/*
   FilterWindingIntoTree_r() - ydnar
   filters a winding from a drawsurface into the tree
 */

static int FilterWindingIntoTree_r( winding_t& w, mapDrawSurface_t& ds, node_t *node ){
	/* get minmax */
	const MinMax& minmax = ds.shaderInfo->minmax;

	/* ydnar: is this the head node? */
	if ( node->parent == nullptr && minmax.valid() ) {
		static bool warned = false;
		if ( !warned ) {
			Sys_Warning( "this map uses the deformVertexes move hack\n" );
			warned = true;
		}

		/* 'fatten' the winding by the shader mins/maxs (parsed from vertexDeform move) */
		/* note this winding is completely invalid (concave, nonplanar, etc) */
		winding_t fat( w.size() * 3 + 3 );
		for ( size_t i = 0; i < w.size(); ++i )
		{
			fat[ i ] = w[ i ];
			fat[ i + ( w.size() + 1 ) ] = w[ i ] + minmax.mins;
			fat[ i + ( w.size() + 1 ) * 2 ] = w[ i ] + minmax.maxs;
		}
		fat[ w.size() ] = w[ 0 ];
		fat[ w.size() * 2 ] = w[ 0 ] + minmax.mins;
		fat[ w.size() * 3 ] = w[ 0 ] + minmax.maxs;

		/*
		 * note: this winding is STILL not suitable for ClipWindingEpsilon, and
		 * also does not really fulfill the intention as it only contains
		 * origin, +mins, +maxs, but thanks to the "closing" points I just
		 * added to the three sub-windings, the fattening at least doesn't make
		 * it worse
		 */

		w.swap( fat );
	}

	/* is this a decision node? */
	if ( node->planenum != PLANENUM_LEAF ) {
		/* get node plane */
		const Plane3f plane1 = mapplanes[ node->planenum ].plane;

		/* check if surface is planar */
		if ( ds.planeNum >= 0 ) {
			#if 0
			/* get surface plane */
			const Plane3f plane2 = mapplanes[ ds.planeNum ].plane;

			/* div0: this is the plague (inaccurate) */
			/* invert surface plane */
			const Plane3f reverse = plane3_flipped( plane2 );

			/* compare planes */
			if ( vector3_dot( plane1.normal(), plane2.normal() ) > 0.999f && std::fabs( plane1.dist() - plane2.dist() ) < 0.001f ) {
				return FilterWindingIntoTree_r( w, ds, node->children[ 0 ] );
			}
			if ( vector3_dot( plane1.normal(), reverse.normal() ) > 0.999f && std::fabs( plane1.dist() - reverse.dist() ) < 0.001f ) {
				return FilterWindingIntoTree_r( w, ds, node->children[ 1 ] );
			}
			#else
			/* div0: this is the cholera (doesn't hit enough) */

			/* the drawsurf might have an associated plane, if so, force a filter here */
			if ( ds.planeNum == node->planenum ) {
				return FilterWindingIntoTree_r( w, ds, node->children[eFront] );
			}
			if ( ds.planeNum == ( node->planenum ^ 1 ) ) {
				return FilterWindingIntoTree_r( w, ds, node->children[eBack] );
			}
			#endif
		}

		/* clip the winding by this plane */
		auto [front, back] = ClipWindingEpsilonStrict( w, plane1, ON_EPSILON ); /* strict; we handle the "winding disappeared" case */

		/* filter by this plane */
		int refs = 0;
		if ( front.empty() && back.empty() ) {
			/* same plane, this is an ugly hack */
			/* but better too many than too few refs */
			winding_t wcopy( w );
			refs += FilterWindingIntoTree_r( wcopy, ds, node->children[eFront] );
			refs += FilterWindingIntoTree_r( w, ds, node->children[eBack] );
		}
		if ( !front.empty() ) {
			refs += FilterWindingIntoTree_r( front, ds, node->children[eFront] );
		}
		if ( !back.empty() ) {
			refs += FilterWindingIntoTree_r( back, ds, node->children[eBack] );
		}

		/* return */
		return refs;
	}

	/* add a reference */
	return AddReferenceToLeaf( ds, node );
}



/*
   FilterFaceIntoTree()
   filters a planar winding face drawsurface into the bsp tree
 */

static int FilterFaceIntoTree( mapDrawSurface_t& ds, tree_t& tree ){
	/* make a winding and filter it into the tree */
	winding_t w = WindingFromDrawSurf( ds );
	int refs = FilterWindingIntoTree_r( w, ds, tree.headnode );

	/* return */
	return refs;
}



/*
   FilterPatchIntoTree()
   subdivides a patch into an approximate curve and filters it into the tree
 */

static int FilterPatchIntoTree( mapDrawSurface_t& ds, tree_t& tree ){
	int refs = 0;

	for ( int y = 0; y + 2 < ds.patchHeight; y += 2 )
		for ( int x = 0; x + 2 < ds.patchWidth; x += 2 )
		{
			const Vector3& p0 = ds.verts[( y + 0 ) * ds.patchWidth + ( x + 0 )].xyz;
			const Vector3& p1 = ds.verts[( y + 0 ) * ds.patchWidth + ( x + 1 )].xyz;
			const Vector3& p2 = ds.verts[( y + 0 ) * ds.patchWidth + ( x + 2 )].xyz;
			const Vector3& p3 = ds.verts[( y + 1 ) * ds.patchWidth + ( x + 0 )].xyz;
			const Vector3& p4 = ds.verts[( y + 1 ) * ds.patchWidth + ( x + 1 )].xyz;
			const Vector3& p5 = ds.verts[( y + 1 ) * ds.patchWidth + ( x + 2 )].xyz;
			const Vector3& p6 = ds.verts[( y + 2 ) * ds.patchWidth + ( x + 0 )].xyz;
			const Vector3& p7 = ds.verts[( y + 2 ) * ds.patchWidth + ( x + 1 )].xyz;
			const Vector3& p8 = ds.verts[( y + 2 ) * ds.patchWidth + ( x + 2 )].xyz;

			// add 4 invariant points + 12 of those which are used to calculate subdivisionless patch LoD
			// convex hull defined by them guaranteedly encompasses any patch LoD
			std::array<Vector3, 16> points = { p0, p2, p6, p8,
				vector3_mid( p0, p1 ), vector3_mid( p1, p2 ),
				vector3_mid( p6, p7 ), vector3_mid( p7, p8 ),
				vector3_mid( p0, p3 ), vector3_mid( p3, p6 ),
				vector3_mid( p2, p5 ), vector3_mid( p5, p8 ) };
			// final curve points
			const Vector3 p1_ = vector3_mid( points[4], points[5] );
			const Vector3 p7_ = vector3_mid( points[6], points[7] );
			const Vector3 p3_ = vector3_mid( points[8], points[9] );
			const Vector3 p5_ = vector3_mid( points[10], points[11] );
			const Vector3 p4_ = ( p1 + p4 * 2 + p7 ) * .25; // PutPointsOnCurve() lerps colums 1st
			// then row pass
			points[12] = vector3_mid( p3_, p4_ );
			points[13] = vector3_mid( p4_, p5_ );
			const Vector3 p4__ = vector3_mid( points[12], points[13] ); // final central point
			// find original central point as if column lerp occured last and produced the final point
			// (a + 2c + b )/4 = f
			// c = (4f - a - b)/2
			const Vector3 p4o = p4__ * 2 - vector3_mid( p1_, p7_ );
			points[14] = vector3_mid( p1_, p4o );
			points[15] = vector3_mid( p4o, p7_ );

			refs += FilterPointConvexHullIntoTree_r( points, ds, tree.headnode );
		}

	return refs;
}



/*
   FilterTrianglesIntoTree()
   filters a triangle surface (meta, model) into the bsp
 */

static int FilterTrianglesIntoTree( mapDrawSurface_t& ds, tree_t& tree ){
	int refs = 0;

	/* ydnar: gs mods: this was creating bogus triangles before */
	for ( auto i = ds.indexes.cbegin(); i != ds.indexes.cend(); i += 3 )
	{
		/* error check */
		if ( *( i + 0 ) >= ds.numVerts() ||
		     *( i + 1 ) >= ds.numVerts() ||
		     *( i + 2 ) >= ds.numVerts() ) {
			Error( "Index %d greater than vertex count %d", *i, ds.numVerts() );
		}

		/* make a triangle winding and filter it into the tree */
		winding_t w{
			ds.verts[ *( i + 0 ) ].xyz,
			ds.verts[ *( i + 1 ) ].xyz,
			ds.verts[ *( i + 2 ) ].xyz };
		refs += FilterWindingIntoTree_r( w, ds, tree.headnode );
	}

	/* use point filtering as well */
	for ( const bspDrawVert_t& vert : ds.verts )
		refs += FilterPointIntoTree_r( vert.xyz, ds, tree.headnode );

	return refs;
}



/*
   FilterFoliageIntoTree()
   filters a foliage surface (wolf et/splash damage)
 */

static int FilterFoliageIntoTree( mapDrawSurface_t& ds, tree_t& tree ){
	/* walk origin list */
	int refs = 0;
	for ( bspDrawVert_t& instance : Span( &ds.verts[ ds.patchHeight ], ds.numFoliageInstances ) )
	{
		/* walk triangle list */
		for ( auto i = ds.indexes.cbegin(); i != ds.indexes.cend(); i += 3 )
		{
			/* error check */
			if ( *( i + 0 ) >= ds.numVerts() ||
			     *( i + 1 ) >= ds.numVerts() ||
			     *( i + 2 ) >= ds.numVerts() ) {
				Error( "Index %d greater than vertex count %d", *i, ds.numVerts() );
			}

			/* make a triangle winding and filter it into the tree */
			winding_t w{
				instance.xyz + ds.verts[ *( i + 0 ) ].xyz,
				instance.xyz + ds.verts[ *( i + 1 ) ].xyz,
				instance.xyz + ds.verts[ *( i + 2 ) ].xyz };
			refs += FilterWindingIntoTree_r( w, ds, tree.headnode );
		}

		/* use point filtering as well */
		for ( const bspDrawVert_t& vert : Span( ds.verts.cbegin(), ds.verts.cend() - ds.numFoliageInstances ) )
		{
			refs += FilterPointIntoTree_r( instance.xyz + vert.xyz, ds, tree.headnode );
		}
	}

	return refs;
}



/*
   FilterFlareIntoTree()
   simple point filtering for flare surfaces
 */
static int FilterFlareSurfIntoTree( mapDrawSurface_t& ds, tree_t& tree ){
	return FilterPointIntoTree_r( ds.lightmapOrigin, ds, tree.headnode );
}



/*
   EmitDrawVerts() - ydnar
   emits bsp drawverts from a map drawsurface
 */

static void EmitDrawVerts( const mapDrawSurface_t& ds, bspDrawSurface_t& out ){
	/* get stuff */
	const float offset = ds.shaderInfo->offset;

	/* copy the verts */
	out.firstVert = bspDrawVerts.size();
	out.numVerts = ds.verts.size();
	for ( const bspDrawVert_t& vert : ds.verts )
	{
		/* allocate a new vert */ /* copy it */
		bspDrawVert_t& dv = bspDrawVerts.emplace_back( vert );

		/* offset? */
		if ( offset != 0 ) {
			dv.xyz += dv.normal * offset;
		}

		/* expand model bounds
		   necessary because of misc_model surfaces on entities
		   note: does not happen on worldspawn as its bounds is only used for determining lightgrid bounds */
		if ( bspModels.size() > 1 ) {
			bspModels.back().minmax.extend( dv.xyz );
		}

		/* debug color? */
		if ( debugSurfaces ) {
			for ( auto& color : dv.color )
				color.rgb() = debugColors[ ( &ds - mapDrawSurfs ) % 12 ];
		}
	}
}



/*
   FindDrawIndexes() - ydnar
   this attempts to find a run of indexes in the bsp that match the given indexes
   this tends to reduce the size of the bsp index pool by 1/3 or more
   returns numIndexes + 1 if the search failed
 */

static int FindDrawIndexes( const DrawIndexes& indexes ){
	const size_t numBSPDrawIndexes = bspDrawIndexes.size();


	/* dummy check */
	if ( indexes.empty() || numBSPDrawIndexes < indexes.size() ) {
		return numBSPDrawIndexes;
	}

	/* set limit */
	const size_t numTestIndexes = 1 + numBSPDrawIndexes - indexes.size();

	/* handle 3 indexes as a special case for performance */
	if ( indexes.size() == 3 ) {
		/* run through all indexes */
		for ( size_t i = 0; i < numTestIndexes; ++i )
		{
			/* test 3 indexes */
			if ( indexes[ 0 ] == bspDrawIndexes[ i + 0 ] &&
			     indexes[ 1 ] == bspDrawIndexes[ i + 1 ] &&
			     indexes[ 2 ] == bspDrawIndexes[ i + 2 ] ) {
				numRedundantIndexes += indexes.size();
				return i;
			}
		}

		/* failed */
		return numBSPDrawIndexes;
	}

	/* handle 4 or more indexes */
	for ( size_t i = 0; i < numTestIndexes; ++i )
	{
		/* test first 4 indexes */
		if ( indexes[ 0 ] == bspDrawIndexes[ i + 0 ] &&
		     indexes[ 1 ] == bspDrawIndexes[ i + 1 ] &&
		     indexes[ 2 ] == bspDrawIndexes[ i + 2 ] &&
		     indexes[ 3 ] == bspDrawIndexes[ i + 3 ] ) {
			/* handle 4 indexes */
			if ( indexes.size() == 4 ) {
				return i;
			}

			/* test the remainder */
			for ( size_t j = 4; j < indexes.size(); ++j )
			{
				if ( indexes[ j ] != bspDrawIndexes[ i + j ] ) {
					break;
				}
				else if ( j == ( indexes.size() - 1 ) ) {
					numRedundantIndexes += indexes.size();
					return i;
				}
			}
		}
	}

	/* failed */
	return numBSPDrawIndexes;
}



/*
   EmitDrawIndexes() - ydnar
   attempts to find an existing run of drawindexes before adding new ones
 */

static void EmitDrawIndexes( const mapDrawSurface_t& ds, bspDrawSurface_t& out ){
	/* attempt to use redundant indexing */
	out.firstIndex = FindDrawIndexes( ds.indexes );
	out.numIndexes = ds.indexes.size();
	if ( out.firstIndex == int( bspDrawIndexes.size() ) ) {
		/* copy new unique indexes */
		for ( int i : ds.indexes )
		{
			int& index = bspDrawIndexes.emplace_back( i );

			/* validate the index */
			if ( ds.type != ESurfaceType::Patch ) {
				if ( index < 0 || index >= ds.numVerts() ) {
					Sys_Warning( "%zu %s has invalid index %d\n",
					             bspDrawSurfaces.size() - 1,
					             ds.shaderInfo->shader.c_str(),
					             index );
					index = 0;
				}
			}
		}
	}
}




/*
   EmitFlareSurface()
   emits a bsp flare drawsurface
 */

static void EmitFlareSurface( mapDrawSurface_t& ds ){
	/* ydnar: nuking useless flare drawsurfaces */
	if ( !emitFlares && ds.type != ESurfaceType::Shader ) {
		return;
	}

	/* allocate a new surface */
	bspDrawSurface_t& out = bspDrawSurfaces.emplace_back();
	ds.outputNum = bspDrawSurfaces.size() - 1;

	/* set it up */
	out.surfaceType = MST_FLARE;
	out.shaderNum = EmitShader( ds.shaderInfo->shader, &ds.shaderInfo->contentFlags, &ds.shaderInfo->surfaceFlags );
	out.fogNum = ds.fogNum;

	/* RBSP */
	out.lightmapStyles = { byte( ds.lightStyle ), LS_NONE, LS_NONE, LS_NONE };
	out.vertexStyles   = { byte( ds.lightStyle ), LS_NONE, LS_NONE, LS_NONE };
	out.lightmapNum.fill( LIGHTMAP_BY_VERTEX );

	out.lightmapOrigin = ds.lightmapOrigin;          /* origin */
	out.lightmapVecs[ 0 ] = ds.lightmapVecs[ 0 ];    /* color */
	out.lightmapVecs[ 1 ] = ds.lightmapVecs[ 1 ];
	out.lightmapVecs[ 2 ] = ds.lightmapVecs[ 2 ];    /* normal */

	/* add to count */
	numSurfacesByType[ static_cast<std::size_t>( ds.type ) ]++;
}

/*
   EmitPatchSurface()
   emits a bsp patch drawsurface
 */

static void EmitPatchSurface( const entity_t& e, mapDrawSurface_t& ds ){
	/* vortex: _patchMeta support */
	const bool forcePatchMeta = e.boolForKey( "_patchMeta", "patchMeta" );

	/* invert the surface if necessary */
	if ( ds.backSide || ds.shaderInfo->invert ) {
		/* walk the verts, flip the normal */
		for ( bspDrawVert_t& vert : ds.verts )
			vector3_negate( vert.normal );

		/* walk the verts again, but this time reverse their order */
		for ( int j = 0; j < ds.patchHeight; ++j )
		{
			for ( int i = 0; i < ( ds.patchWidth / 2 ); ++i )
			{
				std::swap( ds.verts[ j * ds.patchWidth + i ],
				           ds.verts[ j * ds.patchWidth + ( ds.patchWidth - i - 1 ) ] );
			}
		}

		/* invert facing */
		vector3_negate( ds.lightmapVecs[ 2 ] );
	}

	/* allocate a new surface */
	bspDrawSurface_t& out = bspDrawSurfaces.emplace_back();
	ds.outputNum = bspDrawSurfaces.size() - 1;

	/* set it up */
	out.surfaceType = MST_PATCH;
	if ( debugSurfaces ) {
		out.shaderNum = EmitShader( "debugsurfaces", nullptr, nullptr );
	}
	else if ( patchMeta || forcePatchMeta ) {
		/* patch meta requires that we have nodraw patches for collision */
		int surfaceFlags = ds.shaderInfo->surfaceFlags;
		int contentFlags = ds.shaderInfo->contentFlags;
		ApplySurfaceParm( "nodraw", &contentFlags, &surfaceFlags, nullptr );
		ApplySurfaceParm( "pointlight", &contentFlags, &surfaceFlags, nullptr );

		/* we don't want this patch getting lightmapped */
		ds.lightmapVecs[ 2 ].set( 0 );
		ds.lightmapAxis.set( 0 );
		ds.sampleSize = 0;

		/* emit the new fake shader */
		out.shaderNum = EmitShader( ds.shaderInfo->shader, &contentFlags, &surfaceFlags );
	}
	else{
		out.shaderNum = EmitShader( ds.shaderInfo->shader, &ds.shaderInfo->contentFlags, &ds.shaderInfo->surfaceFlags );
	}
	out.patchWidth = ds.patchWidth;
	out.patchHeight = ds.patchHeight;
	out.fogNum = ds.fogNum;

	/* RBSP */
	out.lightmapStyles = { LS_NORMAL, LS_NONE, LS_NONE, LS_NONE };
	out.vertexStyles   = { LS_NORMAL, LS_NONE, LS_NONE, LS_NONE };
	out.lightmapNum.fill( LIGHTMAP_BY_VERTEX );

	/* ydnar: gs mods: previously, the lod bounds were stored in lightmapVecs[ 0 ] and [ 1 ], moved to bounds[ 0 ] and [ 1 ] */
	out.lightmapOrigin = ds.lightmapOrigin;
	out.lightmapVecs[ 0 ] = ds.bounds.mins;
	out.lightmapVecs[ 1 ] = ds.bounds.maxs;
	out.lightmapVecs[ 2 ] = ds.lightmapVecs[ 2 ];

	/* ydnar: gs mods: clear out the plane normal */
	if ( !ds.planar ) {
		out.lightmapVecs[ 2 ].set( 0 );
	}

	/* emit the verts and indexes */
	EmitDrawVerts( ds, out );
	EmitDrawIndexes( ds, out );

	/* add to count */
	numSurfacesByType[ static_cast<std::size_t>( ds.type ) ]++;
}

/*
	Autosprite2Deform() function in vanilla Q3 engine and most of sourceports
	produces inconsistent results, which depend on vertex order and indexing.
	Try to please that windy lady.
*/
static void FixAutosprite2Surface( mapDrawSurface_t& ds ){
	if( ds.verts.size() != 4 || ds.indexes.size() != 6 ){
		Sys_Warning( "autosprite2 surface: ds.numVerts != 4 or ds.numIndexes != 6: must be simple rectangle\n" );
		return;
	}

	Plane3f plane;
	if( !PlaneFromPoints( plane, ds.verts[ds.indexes[0]].xyz, ds.verts[ds.indexes[1]].xyz, ds.verts[ds.indexes[2]].xyz ) ){
		Sys_Warning( "autosprite2 surface: degenerate triangle\n" );
		return;
	}

	// reproduce Autosprite2Deform() calculations
	const int edgeVerts[6][2] = {
		{ 0, 1 },
		{ 0, 2 },
		{ 0, 3 },
		{ 1, 2 },
		{ 1, 3 },
		{ 2, 3 }
	};
	float lengths[2] = { 999999, 999999 };
	int edgeIdx[2] = {0};

	// identify the two shortest edges
	for ( int j = 0; j < 6; ++j ) {
		const float l = vector3_length_squared( ds.verts[edgeVerts[j][0]].xyz - ds.verts[edgeVerts[j][1]].xyz );

		if ( l < lengths[0] ) {
			edgeIdx[1] = edgeIdx[0];
			lengths[1] = lengths[0];
			edgeIdx[0] = j;
			lengths[0] = l;
		} else if ( l < lengths[1] ) {
			edgeIdx[1] = j;
			lengths[1] = l;
		}
	}
	// ref edges
	const bspDrawVert_t *edges[2][2] = { { &ds.verts[ edgeVerts[edgeIdx[0]][0] ], &ds.verts[ edgeVerts[edgeIdx[0]][1] ] },
						                 { &ds.verts[ edgeVerts[edgeIdx[1]][0] ], &ds.verts[ edgeVerts[edgeIdx[1]][1] ] } };

	if( edges[0][0] == edges[1][0]
	 || edges[0][0] == edges[1][1]
	 || edges[0][1] == edges[1][0]
	 || edges[0][1] == edges[1][1] ){
		Sys_Warning( "autosprite2 surface: two shortest edges share a vertex\n" ); // note also fails on exact square
		return;
	}

	// find the midpoints
	const Vector3 mid[2] = { vector3_mid( edges[0][0]->xyz, edges[0][1]->xyz ),
	                         vector3_mid( edges[1][0]->xyz, edges[1][1]->xyz ) };

	// find the vector of the major axis
	const Vector3 major = mid[1] - mid[0];

	// cross this with the view direction to get minor axis
	const Vector3 minor = vector3_cross( major, -plane.normal() );

	/* the rest of Autosprite2Deform() algorithm is srsly hot trash
	   thus simply force the order and indexing, which are known as working */

/*   1-----------2 C      C 1-----------2 A          ^minor
     |           |          |           |            |
   B 0-----------3 A      B 0-----------3            -----------> major  */

	if( vector3_dot( edges[0][1]->xyz - edges[0][0]->xyz, minor ) < 0 )
		std::swap( edges[0][0], edges[0][1] );
	if( vector3_dot( edges[1][1]->xyz - edges[1][0]->xyz, minor ) > 0 )
		std::swap( edges[1][0], edges[1][1] );

	ds.verts.assign( { *edges[0][0], *edges[0][1], *edges[1][0], *edges[1][1] } );
	ds.indexes.assign( { 3, 0, 2, 2, 0, 1 } );
}

/*
   OptimizeTriangleSurface() - ydnar
   optimizes the vertex/index data in a triangle surface
 */

#define VERTEX_CACHE_SIZE   16

static void OptimizeTriangleSurface( mapDrawSurface_t& ds ){
	int first, best, bestScore, score;
	int vertexCache[ VERTEX_CACHE_SIZE + 1 ];       /* one more for optimizing insert */


	/* certain surfaces don't get optimized */
	if ( ds.indexes.size() <= VERTEX_CACHE_SIZE ||
	     ds.shaderInfo->autosprite ) {
		return;
	}

	/* create index scratch pad */
	DrawIndexes indexes = ds.indexes;

	/* setup */
	std::copy_n( indexes.cbegin(), std::min( size_t( VERTEX_CACHE_SIZE + 1 ), ds.indexes.size() ), vertexCache );

	/* add triangles in a vertex cache-aware order */
	for ( auto i = ds.indexes.begin(); i != ds.indexes.end(); i += 3 )
	{
		/* find best triangle given the current vertex cache */
		first = -1;
		best = -1;
		bestScore = -1;
		for ( size_t j = 0; j < ds.indexes.size(); j += 3 )
		{
			/* valid triangle? */
			if ( indexes[ j ] != -1 ) {
				/* set first if necessary */
				if ( first < 0 ) {
					first = j;
				}

				/* score the triangle */
				score = 0;
				for ( int k = 0; k < VERTEX_CACHE_SIZE; ++k )
				{
					if ( indexes[ j ] == vertexCache[ k ] || indexes[ j + 1 ] == vertexCache[ k ] || indexes[ j + 2 ] == vertexCache[ k ] ) {
						score++;
					}
				}

				/* better triangle? */
				if ( score > bestScore ) {
					bestScore = score;
					best = j;
				}

				/* a perfect score of 3 means this triangle's verts are already present in the vertex cache */
				if ( score == 3 ) {
					break;
				}
			}
		}

		/* check if no decent triangle was found, and use first available */
		if ( best < 0 ) {
			best = first;
		}

		/* valid triangle? */
		if ( best >= 0 ) {
			/* add triangle to vertex cache */
			for ( int j = 0; j < 3; ++j )
			{
				int k;
				for ( k = 0; k < VERTEX_CACHE_SIZE; ++k )
				{
					if ( indexes[ best + j ] == vertexCache[ k ] ) {
						break;
					}
				}

				if ( k >= VERTEX_CACHE_SIZE ) {
					/* pop off top of vertex cache */
					for ( k = VERTEX_CACHE_SIZE; k > 0; --k )
						vertexCache[ k ] = vertexCache[ k - 1 ];

					/* add vertex */
					vertexCache[ 0 ] = indexes[ best + j ];
				}
			}

			/* add triangle to surface */
			*( i + 0 ) = indexes[ best + 0 ];
			*( i + 1 ) = indexes[ best + 1 ];
			*( i + 2 ) = indexes[ best + 2 ];

			/* clear from input pool */
			indexes[ best + 0 ] = -1;
			indexes[ best + 1 ] = -1;
			indexes[ best + 2 ] = -1;

			/* sort triangle windings (312 -> 123) */
			while ( *i > *( i + 1 ) || *i > *( i + 2 ) )
			{
				std::swap( *( i + 0 ), *( i + 1 ) );
				std::swap( *( i + 1 ), *( i + 2 ) );
			}
		}
	}
}



/*
   EmitTriangleSurface()
   creates a bsp drawsurface from arbitrary triangle surfaces
 */

static void EmitTriangleSurface( mapDrawSurface_t& ds ){
	/* invert the surface if necessary */
	if ( ds.backSide || ds.shaderInfo->invert ) {
		/* walk the indexes, reverse the triangle order */
		for ( auto i = ds.indexes.begin(); i != ds.indexes.end(); i += 3 )
		{
			std::swap( *i, *( i + 1 ) );
		}

		/* walk the verts, flip the normal */
		for ( bspDrawVert_t& vert : ds.verts )
			vector3_negate( vert.normal );

		/* invert facing */
		vector3_negate( ds.lightmapVecs[ 2 ] );
	}

	if( ds.shaderInfo->autosprite
	 && ds.shaderInfo->shaderText != nullptr
	 && strIstr( ds.shaderInfo->shaderText, "autosprite2" ) != nullptr ){
		FixAutosprite2Surface( ds );
	}

	/* allocate a new surface */
	bspDrawSurface_t& out = bspDrawSurfaces.emplace_back();
	ds.outputNum = bspDrawSurfaces.size() - 1;

	/* ydnar/sd: handle wolf et foliage surfaces */
	if ( ds.type == ESurfaceType::Foliage ) {
		out.surfaceType = MST_FOLIAGE;
	}

	/* ydnar: gs mods: handle lightmapped terrain (force to planar type) */
	//%	else if( vector3_length( ds.lightmapAxis ) == 0 || ds.type == ESurfaceType::Triangles || ds.type == ESurfaceType::Foghull || debugSurfaces )
	else if ( ( ds.lightmapAxis == g_vector3_identity && !ds.planar ) ||
	          ds.type == ESurfaceType::Triangles ||
	          ds.type == ESurfaceType::Foghull ||
	          ds.numVerts() > maxLMSurfaceVerts ||
	          debugSurfaces ) {
		out.surfaceType = MST_TRIANGLE_SOUP;
	}

	/* set to a planar face */
	else{
		out.surfaceType = MST_PLANAR;
	}

	/* set it up */
	if ( debugSurfaces ) {
		out.shaderNum = EmitShader( "debugsurfaces", nullptr, nullptr );
	}
	else{
		out.shaderNum = EmitShader( ds.shaderInfo->shader, &ds.shaderInfo->contentFlags, &ds.shaderInfo->surfaceFlags );
	}
	out.patchWidth = ds.patchWidth;
	out.patchHeight = ds.patchHeight;
	out.fogNum = ds.fogNum;

	/* debug inset (push each triangle vertex towards the center of each triangle it is on */
	if ( debugInset ) {
		/* walk triangle list */
		for ( auto i = ds.indexes.begin(); i != ds.indexes.end(); i += 3 )
		{
			/* get verts */
			bspDrawVert_t
			&a = ds.verts[ *( i + 0 ) ],
			&b = ds.verts[ *( i + 1 ) ],
			&c = ds.verts[ *( i + 2 ) ];

			/* calculate centroid */
			const Vector3 cent = ( a.xyz + b.xyz + c.xyz ) / 3;

			/* offset each vertex */
			a.xyz += VectorNormalized( cent - a.xyz );
			b.xyz += VectorNormalized( cent - b.xyz );
			c.xyz += VectorNormalized( cent - c.xyz );
		}
	}

	/* RBSP */
	out.lightmapStyles = { LS_NORMAL, LS_NONE, LS_NONE, LS_NONE };
	out.vertexStyles   = { LS_NORMAL, LS_NONE, LS_NONE, LS_NONE };
	out.lightmapNum.fill( LIGHTMAP_BY_VERTEX );

	/* lightmap vectors (lod bounds for patches) */
	out.lightmapOrigin = ds.lightmapOrigin;
	out.lightmapVecs[ 0 ] = ds.lightmapVecs[ 0 ];
	out.lightmapVecs[ 1 ] = ds.lightmapVecs[ 1 ];
	out.lightmapVecs[ 2 ] = ds.lightmapVecs[ 2 ];

	/* ydnar: gs mods: clear out the plane normal */
	if ( !ds.planar ) {
		out.lightmapVecs[ 2 ].set( 0 );
	}

	/* optimize the surface's triangles */
	OptimizeTriangleSurface( ds );

	/* emit the verts and indexes */
	EmitDrawVerts( ds, out );
	EmitDrawIndexes( ds, out );

	/* add to count */
	numSurfacesByType[ static_cast<std::size_t>( ds.type ) ]++;
}



/*
   EmitFaceSurface()
   emits a bsp planar winding (brush face) drawsurface
 */

static void EmitFaceSurface( mapDrawSurface_t& ds ){
	/* strip/fan finding was moved elsewhere */
	if ( maxAreaFaceSurface ) {
		MaxAreaFaceSurface( ds );
	}
	else{
		StripFaceSurface( ds );
	}
	EmitTriangleSurface( ds );
}


/*
   MakeDebugPortalSurfs_r() - ydnar
   generates drawsurfaces for passable portals in the bsp
 */

static void MakeDebugPortalSurfs_r( const node_t *node, shaderInfo_t& si ){
	/* recurse if decision node */
	if ( node->planenum != PLANENUM_LEAF ) {
		MakeDebugPortalSurfs_r( node->children[ 0 ], si );
		MakeDebugPortalSurfs_r( node->children[ 1 ], si );
		return;
	}

	/* don't bother with opaque leaves */
	if ( node->opaque ) {
		return;
	}

	/* walk the list of portals */
	int c = 0;
	for ( const portal_t *p = node->portals; p != nullptr; ++c, p = p->nextPortal( node ) )
	{
		/* get winding and side even/odd */
		const winding_t& w = p->winding;

		/* is this a valid portal for this leaf? */
		if ( !w.empty() && p->nodes[eFront] == node ) {
			/* is this portal passable? */
			if ( !PortalPassable( p ) ) {
				continue;
			}

			/* check max points */
			if ( w.size() > 64 ) {
				Error( "MakePortalSurfs_r: w->numpoints = %zu", w.size() );
			}

			/* allocate a drawsurface */
			mapDrawSurface_t& ds = AllocDrawSurface( ESurfaceType::Face, si );
			ds.planar = true;
			ds.planeNum = FindFloatPlane( p->plane.plane );
			ds.lightmapVecs[ 2 ] = p->plane.normal();
			ds.fogNum = FOG_INVALID;
			ds.verts.resize( w.size(), c_bspDrawVert_t0 );

			/* walk the winding */
			for ( size_t i = 0; i < w.size(); ++i )
			{
				/* get vert */
				bspDrawVert_t& dv = ds.verts[ i ];

				/* set it */
				dv.xyz = w[ i ];
				dv.normal = p->plane.normal();
				dv.st = Vector2( 0 );
				dv.color.fill( Color4b( debugColors[ c % 12 ], 32 ) );
			}
		}
	}
}



/*
   MakeDebugPortalSurfs() - ydnar
   generates drawsurfaces for passable portals in the bsp
 */

void MakeDebugPortalSurfs( const tree_t& tree ){
	/* note it */
	Sys_FPrintf( SYS_VRB, "--- MakeDebugPortalSurfs ---\n" );

	/* walk the tree */
	MakeDebugPortalSurfs_r( tree.headnode, ShaderInfoForShader( "debugportals" ) );
}



/*
   MakeFogHullSurfs()
   generates drawsurfaces for a foghull (this MUST use a sky shader)
 */

void MakeFogHullSurfs( const char *shader ){
	int indexes[] =
	{
		0, 1, 2, 0, 2, 3,
		4, 7, 5, 5, 7, 6,
		1, 5, 6, 1, 6, 2,
		0, 4, 5, 0, 5, 1,
		2, 6, 7, 2, 7, 3,
		3, 7, 4, 3, 4, 0
	};


	/* dummy check */
	if ( strEmptyOrNull( shader ) ) {
		return;
	}

	/* note it */
	Sys_FPrintf( SYS_VRB, "--- MakeFogHullSurfs ---\n" );

	/* get hull bounds */
	const Vector3 fogMins = g_mapMinmax.mins - Vector3( 128 );
	const Vector3 fogMaxs = g_mapMinmax.maxs + Vector3( 128 );

	/* allocate a drawsurface */
	mapDrawSurface_t& ds = AllocDrawSurface( ESurfaceType::Foghull, ShaderInfoForShader( shader ) );
	ds.fogNum = FOG_INVALID;
	ds.verts.resize( 8, c_bspDrawVert_t0 );

	/* set verts */
	ds.verts[ 0 ].xyz = { fogMins[ 0 ], fogMins[ 1 ], fogMins[ 2 ] };
	ds.verts[ 1 ].xyz = { fogMins[ 0 ], fogMaxs[ 1 ], fogMins[ 2 ] };
	ds.verts[ 2 ].xyz = { fogMaxs[ 0 ], fogMaxs[ 1 ], fogMins[ 2 ] };
	ds.verts[ 3 ].xyz = { fogMaxs[ 0 ], fogMins[ 1 ], fogMins[ 2 ] };

	ds.verts[ 4 ].xyz = { fogMins[ 0 ], fogMins[ 1 ], fogMaxs[ 2 ] };
	ds.verts[ 5 ].xyz = { fogMins[ 0 ], fogMaxs[ 1 ], fogMaxs[ 2 ] };
	ds.verts[ 6 ].xyz = { fogMaxs[ 0 ], fogMaxs[ 1 ], fogMaxs[ 2 ] };
	ds.verts[ 7 ].xyz = { fogMaxs[ 0 ], fogMins[ 1 ], fogMaxs[ 2 ] };

	/* set indexes */
	ds.indexes.assign( std::cbegin( indexes ), std::cend( indexes ) );
}



/*
   BiasSurfaceTextures()
   biases a surface's texcoords as close to 0 as possible
 */

static void BiasSurfaceTextures( mapDrawSurface_t& ds ){
	/* don't bias globaltextured shaders */
	if ( ds.shaderInfo->globalTexture ) {
		return;
	}

	/* calculate the surface texture bias */
	const Vector2 bias = CalcSurfaceTextureBias( ds );

	/* bias the texture coordinates */
	for ( bspDrawVert_t& vert : ds.verts )
	{
		vert.st -= bias;
	}
}



/*
   AddSurfaceModelsToTriangle_r()
   adds models to a specified triangle, returns the number of models added
 */

static int AddSurfaceModelsToTriangle_r( const mapDrawSurface_t& ds, const surfaceModel_t& model, const TriRef& tri, entity_t& entity ){
	int max, n, localNumSurfaceModels;


	/* init */
	localNumSurfaceModels = 0;

	/* subdivide calc */
	{
		/* find the longest edge and split it */
		max = -1;
		float maxDist = 0;
		for ( int i = 0; i < 3; ++i )
		{
			/* get dist */
			const float dist = vector3_length_squared( tri[ i ]->xyz - tri[ ( i + 1 ) % 3 ]->xyz );

			/* longer? */
			if ( dist > maxDist ) {
				maxDist = dist;
				max = i;
			}
		}

		/* is the triangle small enough? */
		if ( max < 0 || maxDist <= ( model.density * model.density ) ) {
			float odds, r, angle;
			Vector3 axis[ 3 ];


			/* roll the dice (model's odds scaled by vertex alpha) */
			odds = model.odds * ( tri[ 0 ]->color[ 0 ].alpha() + tri[ 0 ]->color[ 0 ].alpha() + tri[ 0 ]->color[ 0 ].alpha() ) / 765.0f;
			r = Random();
			if ( r > odds ) {
				return 0;
			}

			/* calculate scale */
			r = model.minScale + Random() * ( model.maxScale - model.minScale );
			const Vector3 scale( r );

			/* calculate angle */
			angle = model.minAngle + Random() * ( model.maxAngle - model.minAngle );

			/* set angles */
			const Vector3 angles( 0, 0, angle );

			/* calculate average origin */
			const Vector3 origin = ( tri[ 0 ]->xyz + tri[ 1 ]->xyz + tri[ 2 ]->xyz ) / 3;

			/* clear transform matrix */
			Matrix4 transform( g_matrix4_identity );

			/* handle oriented models */
			if ( model.oriented ) {
				/* calculate average normal */
				axis[ 2 ] = tri[ 0 ]->normal + tri[ 1 ]->normal + tri[ 2 ]->normal;
				if ( VectorNormalize( axis[ 2 ] ) == 0 ) {
					axis[ 2 ] = tri[ 0 ]->normal;
				}

				/* make perpendicular vectors */
				MakeNormalVectors( axis[ 2 ], axis[ 1 ], axis[ 0 ] );

				/* copy to matrix */
				Matrix4 temp( g_matrix4_identity );
				temp.x().vec3() = axis[0];
				temp.y().vec3() = axis[1];
				temp.z().vec3() = axis[2];

				/* scale */
				matrix4_scale_by_vec3( temp, scale );

				/* rotate around z axis */
				matrix4_rotate_by_euler_xyz_degrees( temp, angles );

				/* translate */
				matrix4_translate_by_vec3( transform, origin );

				/* transform into axis space */
				matrix4_multiply_by_matrix4( transform, temp );
			}

			/* handle z-up models */
			else
			{
				/* set matrix */
				matrix4_transform_by_euler_xyz_degrees( transform, origin, angles, scale );
			}

			/* insert the model */
			InsertModel( model.model.c_str(), nullptr, 0, transform, nullptr, entity, 0, clipDepthGlobal,
				EntityCompileParams{
					.castShadows   = ds.castShadows,
					.recvShadows   = ds.recvShadows,
					.celShader     = ds.celShader,
					.lightmapSampleSize = 0,
					.lightmapScale = ds.lightmapScale,
					.shadeAngle = 0,
					.ambientColor  = ds.ambientColor
				} );
			/* return to sender */
			return 1;
		}
	}

	/* split the longest edge and map it */
	const bspDrawVert_t mid = LerpDrawVert( *tri[ max ], *tri[ ( max + 1 ) % 3 ] );

	/* recurse to first triangle */
	TriRef tri2 = tri;
	tri2[ max ] = &mid;
	n = AddSurfaceModelsToTriangle_r( ds, model, tri2, entity );
	if ( n < 0 ) {
		return n;
	}
	localNumSurfaceModels += n;

	/* recurse to second triangle */
	tri2 = tri;
	tri2[ ( max + 1 ) % 3 ] = &mid;
	n = AddSurfaceModelsToTriangle_r( ds, model, tri2, entity );
	if ( n < 0 ) {
		return n;
	}
	localNumSurfaceModels += n;

	/* return count */
	return localNumSurfaceModels;
}



/*
   AddSurfaceModels()
   adds a surface's shader models to the surface
 */

static int AddSurfaceModels( const mapDrawSurface_t& ds, entity_t& entity ){
	/* init */
	int localNumSurfaceModels = 0;

	/* walk the model list */
	for ( const auto& model : ds.shaderInfo->surfaceModels )
	{
		/* switch on type */
		switch ( ds.type )
		{
		/* handle brush faces and decals */
		case ESurfaceType::Face:
		case ESurfaceType::Decal:
		{
			/* calculate centroid */
			bspDrawVert_t centroid = c_bspDrawVert_t0;
			float alpha = 0;

			/* walk verts */
			for ( const bspDrawVert_t& vert : ds.verts )
			{
				centroid.xyz += vert.xyz;
				centroid.normal += vert.normal;
				centroid.st += vert.st;
				alpha += vert.color[ 0 ].alpha();
			}

			/* average */
			centroid.xyz /= ds.verts.size();
			if ( VectorNormalize( centroid.normal ) == 0 ) {
				centroid.normal = ds.verts[ 0 ].normal;
			}
			centroid.st /= ds.verts.size();
			centroid.color[ 0 ] = { 255, 255, 255, color_to_byte( alpha / ds.verts.size() ) };

			/* walk fanned triangles */
			for ( auto prev = ds.verts.cend() - 1, next = ds.verts.cbegin(); next != ds.verts.cend(); prev = next++ )
			{
				/* create models */
				const int n = AddSurfaceModelsToTriangle_r( ds, model, TriRef{
					&centroid, /* head vert is centroid */
					prev.operator->(),
					next.operator->() }, entity );
				if ( n < 0 ) {
					return n;
				}
				localNumSurfaceModels += n;
			}
			break;
		}
		/* handle patches */
		case ESurfaceType::Patch:
		{
			/* subdivide the surface */
			const mesh_t mesh = TessellatedMesh( mesh_view_t( ds.patchWidth, ds.patchHeight, ds.verts.data() ), IterationsForCurve( ds.longestCurve, patchSubdivisions ) );

			/* subdivide each quad to place the models */
			for( MeshQuadIterator it( mesh ); it; ++it ){
				for( const TriRef& tri : it.tris() )
				{
					const int n = AddSurfaceModelsToTriangle_r( ds, model, tri, entity );
					if ( n < 0 ) {
						return n;
					}
					localNumSurfaceModels += n;
				}
			}
			break;
		}
		/* handle triangle surfaces */
		case ESurfaceType::Triangles:
		case ESurfaceType::ForcedMeta:
		case ESurfaceType::Meta:
			/* walk the triangle list */
			for ( auto i = ds.indexes.cbegin(); i != ds.indexes.cend(); i += 3 )
			{
				const int n = AddSurfaceModelsToTriangle_r( ds, model, TriRef{
					&ds.verts[ *( i + 0 ) ],
					&ds.verts[ *( i + 1 ) ],
					&ds.verts[ *( i + 2 ) ] }, entity );
				if ( n < 0 ) {
					return n;
				}
				localNumSurfaceModels += n;
			}
			break;

		/* no support for flares, foghull, etc */
		default:
			break;
		}
	}

	/* return count */
	return localNumSurfaceModels;
}



/*
   AddEntitySurfaceModels() - ydnar
   adds surfacemodels to an entity's surfaces
 */

void AddEntitySurfaceModels( entity_t& e ){
	/* note it */
	Sys_FPrintf( SYS_VRB, "--- AddEntitySurfaceModels ---\n" );

	/* walk the surface list */ /* numMapDrawSurfs grows here; do we want SurfaceModels on model surfaces? (can create infinite loop) */
	for ( int i = e.firstDrawSurf; i < numMapDrawSurfs; ++i )
		numSurfaceModels += AddSurfaceModels( mapDrawSurfs[ i ], e );
}



/*
   VolumeColorMods() - ydnar
   applies brush/volumetric color/alpha modulation to vertexes
 */

static void VolumeColorMods( const entity_t& e, mapDrawSurface_t& ds ){
	/* iterate brushes */
	for ( const brush_t *b : e.colorModBrushes )
	{
		/* worldspawn alpha brushes affect all, grouped ones only affect original entity */
		if ( b->entityNum != 0 && b->entityNum != ds.entityNum ) {
			continue;
		}

		/* test bbox */
		if ( !b->minmax.test( ds.minmax ) ) {
			continue;
		}

		/* iterate verts */
		for ( bspDrawVert_t& vert : ds.verts )
		{
			if( std::ranges::none_of( b->sides, [&vert]( const side_t& side ){
				return plane3_distance_to_point( mapplanes[ side.planenum ].plane, vert.xyz ) > 1; /* point-plane test */
			} ) )
				/* apply colormods */
				ColorMod( b->contentShader->colorMod, Span( &vert, 1 ) );
		}
	}
}



/*
   FilterDrawsurfsIntoTree()
   upon completion, all drawsurfs that actually generate a reference
   will have been emitted to the bspfile arrays, and the references
   will have valid final indexes
 */

void FilterDrawsurfsIntoTree( entity_t& e, tree_t& tree ){
	int refs;
	int numSurfs, numRefs, numSkyboxSurfaces;
	bool sb;


	/* note it */
	Sys_FPrintf( SYS_VRB, "--- FilterDrawsurfsIntoTree ---\n" );

	/* filter surfaces into the tree */
	numSurfs = 0;
	numRefs = 0;
	numSkyboxSurfaces = 0;
	/* numMapDrawSurfs can grow here */
	for ( int i = e.firstDrawSurf; i < numMapDrawSurfs; ++i )
	{
		/* get surface and try to early out */
		mapDrawSurface_t& ds = mapDrawSurfs[ i ];
		if ( ds.verts.empty() && ds.type != ESurfaceType::Flare && ds.type != ESurfaceType::Shader ) {
			continue;
		}

		/* get shader */
		shaderInfo_t *si = ds.shaderInfo;

		/* ydnar: skybox surfaces are special */ /* these are ones generated by MakeSkyboxSurface() */
		if ( ds.skybox ) {
			refs = AddReferenceToTree_r( ds, tree.headnode, true );
			ds.skybox = false;
			sb = true;
		}
		else
		{
			sb = false;

			/* refs initially zero */
			refs = 0;

			/* apply texture coordinate mods */
			for ( bspDrawVert_t& vert : ds.verts )
				TCMod( si->mod, vert.st );

			/* ydnar: apply shader colormod */
			ColorMod( ds.shaderInfo->colorMod, Span( ds.verts ) );

			/* ydnar: apply brush colormod */
			VolumeColorMods( e, ds );

			/* ydnar: make fur surfaces */
			if ( si->furNumLayers > 0 ) {
				Fur( ds );
			}

			/* ydnar/sd: make foliage surfaces */
			if ( !si->foliage.empty() ) {
				Foliage( ds, e );
			}

			/* create a flare surface if necessary */
			if ( !strEmptyOrNull( si->flareShader ) ) {
				AddSurfaceFlare( ds, e.origin );
			}

			/* ydnar: don't emit nodraw surfaces (like nodraw fog) */
			if ( ( si->compileFlags & C_NODRAW ) && ds.type != ESurfaceType::Patch ) {
				continue;
			}

			/* ydnar: bias the surface textures */
			BiasSurfaceTextures( ds );

			/* ydnar: globalizing of fog volume handling (eek a hack) */
			if ( &e != &entities[0] && !si->noFog ) {
				/* offset surface by entity origin */
				const MinMax minmax( ds.minmax.mins + e.origin, ds.minmax.maxs + e.origin );

				/* set the fog number for this surface */
				ds.fogNum = FogForBounds( minmax, 1.0f );  //%	FogForPoint( origin, 0.0f );
			}
		}

		/* ydnar: remap shader */
/*		if ( !strEmptyOrNull( ds->shaderInfo->remapShader ) ) {
			ds->shaderInfo = &ShaderInfoForShader( ds->shaderInfo->remapShader );
		}
*/
		/* ydnar: gs mods: handle the various types of surfaces */
		switch ( ds.type )
		{
		/* handle brush faces */
		case ESurfaceType::Face:
		case ESurfaceType::Decal:
			if ( refs == 0 ) {
				refs = FilterFaceIntoTree( ds, tree );
			}
			if ( refs > 0 ) {
				EmitFaceSurface( ds );
			}
			break;

		/* handle patches */
		case ESurfaceType::Patch:
			if ( refs == 0 ) {
				refs = FilterPatchIntoTree( ds, tree );
			}
			if ( refs > 0 ) {
				EmitPatchSurface( e, ds );
			}
			break;

		/* handle triangle surfaces */
		case ESurfaceType::Triangles:
		case ESurfaceType::ForcedMeta:
		case ESurfaceType::Meta:
			//%	Sys_FPrintf( SYS_VRB, "Surface %4d: [%1d] %4d verts %s\n", numSurfs, ds->planar, ds->numVerts, si->shader );
			if ( refs == 0 ) {
				refs = FilterTrianglesIntoTree( ds, tree );
			}
			if ( refs > 0 ) {
				EmitTriangleSurface( ds );
			}
			break;

		/* handle foliage surfaces (splash damage/wolf et) */
		case ESurfaceType::Foliage:
			//%	Sys_FPrintf( SYS_VRB, "Surface %4d: [%d] %4d verts %s\n", numSurfs, ds->numFoliageInstances, ds->numVerts, si->shader );
			if ( refs == 0 ) {
				refs = FilterFoliageIntoTree( ds, tree );
			}
			if ( refs > 0 ) {
				EmitTriangleSurface( ds );
			}
			break;

		/* handle foghull surfaces */
		case ESurfaceType::Foghull:
			if ( refs == 0 ) {
				refs = AddReferenceToTree_r( ds, tree.headnode, false );
			}
			if ( refs > 0 ) {
				EmitTriangleSurface( ds );
			}
			break;

		/* handle flares */
		case ESurfaceType::Flare:
			if ( refs == 0 ) {
				refs = FilterFlareSurfIntoTree( ds, tree );
			}
			if ( refs > 0 ) {
				EmitFlareSurface( ds );
			}
			break;

		/* handle shader-only surfaces */
		case ESurfaceType::Shader:
			refs = 1;
			EmitFlareSurface( ds );
			break;

		/* no references */
		default:
			refs = 0;
			break;
		}

		/* maybe surface got marked as skybox again */
		/* if we keep that flag, it will get scaled up AGAIN */
		if ( sb ) {
			ds.skybox = false;
		}

		/* tot up the references */
		if ( refs > 0 ) {
			/* tot up counts */
			numSurfs++;
			numRefs += refs;

			/* emit extra surface data */
			SetSurfaceExtra( ds );
			//%	Sys_FPrintf( SYS_VRB, "%d verts %d indexes\n", ds->numVerts, ds->numIndexes );

			/* one last sanity check */
			{
				const bspDrawSurface_t& out = bspDrawSurfaces.back();
				if ( out.numVerts == 3 && out.numIndexes > 3 ) {
					Sys_Printf( "\n" );
					Sys_Warning( "Potentially bad %s surface (%zu: %d, %d)\n     %s\n",
					             surfaceTypeName( ds.type ),
					             bspDrawSurfaces.size(), out.numVerts, out.numIndexes, si->shader.c_str() );
				}
			}

			/* ydnar: handle skybox surfaces */ /* these are ones found in _skybox area */
			if ( ds.skybox ) {
				MakeSkyboxSurface( ds );
				numSkyboxSurfaces++;
			}
		}
	}

	/* emit some statistics */
	Sys_FPrintf( SYS_VRB, "%9d references\n", numRefs );
	Sys_FPrintf( SYS_VRB, "%9d (%zu) emitted drawsurfs\n", numSurfs, bspDrawSurfaces.size() );
	Sys_FPrintf( SYS_VRB, "%9d stripped face surfaces\n", numStripSurfaces );
	Sys_FPrintf( SYS_VRB, "%9d fanned face surfaces\n", numFanSurfaces );
	Sys_FPrintf( SYS_VRB, "%9d maxarea'd face surfaces\n", numMaxAreaSurfaces );
	Sys_FPrintf( SYS_VRB, "%9d surface models generated\n", numSurfaceModels );
	Sys_FPrintf( SYS_VRB, "%9d skybox surfaces generated\n", numSkyboxSurfaces );
	for ( std::size_t i = 0; i < std::size( numSurfacesByType ); ++i )
		Sys_FPrintf( SYS_VRB, "%9d %s surfaces\n", numSurfacesByType[ i ], surfaceTypeName( static_cast<ESurfaceType>( i ) ) );

	Sys_FPrintf( SYS_VRB, "%9d redundant indexes suppressed, saving %d Kbytes\n", numRedundantIndexes, ( numRedundantIndexes * 4 / 1024 ) );
}