csg.c

/*
===========================================================================

Return to Castle Wolfenstein single player GPL Source Code
Copyright (C) 1999-2010 id Software LLC, a ZeniMax Media company. 

This file is part of the Return to Castle Wolfenstein single player GPL Source Code (“RTCW SP Source Code”).  

RTCW SP Source Code 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 3 of the License, or
(at your option) any later version.

RTCW SP Source Code 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 RTCW SP Source Code.  If not, see <http://www.gnu.org/licenses/>.

In addition, the RTCW SP Source Code is also subject to certain additional terms. You should have received a copy of these additional terms immediately following the terms and conditions of the GNU General Public License which accompanied the RTCW SP Source Code.  If not, please request a copy in writing from id Software at the address below.

If you have questions concerning this license or the applicable additional terms, you may contact in writing id Software LLC, c/o ZeniMax Media Inc., Suite 120, Rockville, Maryland 20850 USA.

===========================================================================
*/

//===========================================================================
//
// Name:				Brush CSG
// Function:
// Programmer(s):	id Software & Mr Elusive (MrElusive@demigod.demon.nl)
// Last update:	1997-12-04
// Tab Size:		3
// Notes:			Microsoft Visual C++ optimizations:
//						"global optimization" or "full optimization" results
//						in micro brushes??
//===========================================================================

#include "qbsp.h"

/*

tag all brushes with original contents
brushes may contain multiple contents
there will be no brush overlap after csg phase

*/

int minplanenums[3];
int maxplanenums[3];

//===========================================================================
//
// Parameter:				-
// Returns:					-
// Changes Globals:		-
//===========================================================================
void CheckBSPBrush( bspbrush_t *brush ) {
	int i, j;
	plane_t *plane1, *plane2;

	//check if the brush is convex... flipped planes make a brush non-convex
	for ( i = 0; i < brush->numsides; i++ )
	{
		for ( j = 0; j < brush->numsides; j++ )
		{
			if ( i == j ) {
				continue;
			}
			plane1 = &mapplanes[brush->sides[i].planenum];
			plane2 = &mapplanes[brush->sides[j].planenum];
			//
			if ( WindingsNonConvex( brush->sides[i].winding,
									brush->sides[j].winding,
									plane1->normal, plane2->normal,
									plane1->dist, plane2->dist ) ) {
				Log_Print( "non convex brush" );
				break;
			} //end if
		} //end for
	} //end for
	BoundBrush( brush );
	//check for out of bound brushes
	for ( i = 0; i < 3; i++ )
	{
		if ( brush->mins[i] < -MAX_MAP_BOUNDS || brush->maxs[i] > MAX_MAP_BOUNDS ) {
			Log_Print( "brush: bounds out of range\n" );
			Log_Print( "ob->mins[%d] = %f, ob->maxs[%d] = %f\n", i, brush->mins[i], i, brush->maxs[i] );
			break;
		} //end if
		if ( brush->mins[i] > MAX_MAP_BOUNDS || brush->maxs[i] < -MAX_MAP_BOUNDS ) {
			Log_Print( "brush: no visible sides on brush\n" );
			Log_Print( "ob->mins[%d] = %f, ob->maxs[%d] = %f\n", i, brush->mins[i], i, brush->maxs[i] );
			break;
		} //end if
	} //end for
} //end of the function CheckBSPBrush
//===========================================================================
//
// Parameter:				-
// Returns:					-
// Changes Globals:		-
//===========================================================================
void BSPBrushWindings( bspbrush_t *brush ) {
	int i, j;
	winding_t *w;
	plane_t *plane;

	for ( i = 0; i < brush->numsides; i++ )
	{
		plane = &mapplanes[brush->sides[i].planenum];
		w = BaseWindingForPlane( plane->normal, plane->dist );
		for ( j = 0; j < brush->numsides && w; j++ )
		{
			if ( i == j ) {
				continue;
			}
			plane = &mapplanes[brush->sides[j].planenum ^ 1];
			ChopWindingInPlace( &w, plane->normal, plane->dist, 0 ); //CLIP_EPSILON);
		} //end for
		brush->sides[i].winding = w;
	} //end for
} //end of the function BSPBrushWindings
//===========================================================================
// NOTE: can't keep brush->original intact
//
// Parameter:				-
// Returns:					-
// Changes Globals:		-
//===========================================================================
bspbrush_t *TryMergeBrushes( bspbrush_t *brush1, bspbrush_t *brush2 ) {
	int i, j, k, n, shared;
	side_t *side1, *side2, *cs;
	plane_t *plane1, *plane2;
	bspbrush_t *newbrush;

	//check for bounding box overlapp
	for ( i = 0; i < 3; i++ )
	{
		if ( brush1->mins[i] > brush2->maxs[i] + 2
			 || brush1->maxs[i] < brush2->mins[i] - 2 ) {
			return NULL;
		} //end if
	} //end for
	  //
	shared = 0;
	//check if the brush is convex... flipped planes make a brush non-convex
	for ( i = 0; i < brush1->numsides; i++ )
	{
		side1 = &brush1->sides[i];
		//don't check the "shared" sides
		for ( k = 0; k < brush2->numsides; k++ )
		{
			side2 = &brush2->sides[k];
			if ( side1->planenum == ( side2->planenum ^ 1 ) ) {
				shared++;
				//there may only be ONE shared side
				if ( shared > 1 ) {
					return NULL;
				}
				break;
			} //end if
		} //end for
		if ( k < brush2->numsides ) {
			continue;
		}
		//
		for ( j = 0; j < brush2->numsides; j++ )
		{
			side2 = &brush2->sides[j];
			//don't check the "shared" sides
			for ( n = 0; n < brush1->numsides; n++ )
			{
				side1 = &brush1->sides[n];
				if ( side1->planenum == ( side2->planenum ^ 1 ) ) {
					break;
				}
			} //end for
			if ( n < brush1->numsides ) {
				continue;
			}
			//
			side1 = &brush1->sides[i];
			//if the side is in the same plane
			//*
			if ( side1->planenum == side2->planenum ) {
				if ( side1->texinfo != TEXINFO_NODE &&
					 side2->texinfo != TEXINFO_NODE &&
					 side1->texinfo != side2->texinfo ) {
					return NULL;
				}
				continue;
			} //end if
			  //
			plane1 = &mapplanes[side1->planenum];
			plane2 = &mapplanes[side2->planenum];
			//
			if ( WindingsNonConvex( side1->winding, side2->winding,
									plane1->normal, plane2->normal,
									plane1->dist, plane2->dist ) ) {
				return NULL;
			} //end if
		} //end for
	} //end for
	newbrush = AllocBrush( brush1->numsides + brush2->numsides );
	newbrush->original = brush1->original;
	newbrush->numsides = 0;
	//newbrush->side = brush1->side;	//brush contents
	//fix texinfos for sides lying in the same plane
	for ( i = 0; i < brush1->numsides; i++ )
	{
		side1 = &brush1->sides[i];
		//
		for ( n = 0; n < brush2->numsides; n++ )
		{
			side2 = &brush2->sides[n];
			//if both sides are in the same plane get the texinfo right
			if ( side1->planenum == side2->planenum ) {
				if ( side1->texinfo == TEXINFO_NODE ) {
					side1->texinfo = side2->texinfo;
				}
				if ( side2->texinfo == TEXINFO_NODE ) {
					side2->texinfo = side1->texinfo;
				}
			} //end if
		} //end for
	} //end for
	  //
	for ( i = 0; i < brush1->numsides; i++ )
	{
		side1 = &brush1->sides[i];
		//don't add the "shared" sides
		for ( n = 0; n < brush2->numsides; n++ )
		{
			side2 = &brush2->sides[n];
			if ( side1->planenum == ( side2->planenum ^ 1 ) ) {
				break;
			}
		} //end for
		if ( n < brush2->numsides ) {
			continue;
		}
		//
		for ( n = 0; n < newbrush->numsides; n++ )
		{
			cs = &newbrush->sides[n];
			if ( cs->planenum == side1->planenum ) {
				Log_Print( "brush duplicate plane\n" );
				break;
			} //end if
		} //end if
		if ( n < newbrush->numsides ) {
			continue;
		}
		//add this side
		cs = &newbrush->sides[newbrush->numsides];
		newbrush->numsides++;
		*cs = *side1;
	} //end for
	for ( j = 0; j < brush2->numsides; j++ )
	{
		side2 = &brush2->sides[j];
		for ( n = 0; n < brush1->numsides; n++ )
		{
			side1 = &brush1->sides[n];
			//if the side is in the same plane
			if ( side2->planenum == side1->planenum ) {
				break;
			}
			//don't add the "shared" sides
			if ( side2->planenum == ( side1->planenum ^ 1 ) ) {
				break;
			}
		} //end for
		if ( n < brush1->numsides ) {
			continue;
		}
		//
		for ( n = 0; n < newbrush->numsides; n++ )
		{
			cs = &newbrush->sides[n];
			if ( cs->planenum == side2->planenum ) {
				Log_Print( "brush duplicate plane\n" );
				break;
			} //end if
		} //end if
		if ( n < newbrush->numsides ) {
			continue;
		}
		//add this side
		cs = &newbrush->sides[newbrush->numsides];
		newbrush->numsides++;
		*cs = *side2;
	} //end for
	BSPBrushWindings( newbrush );
	BoundBrush( newbrush );
	CheckBSPBrush( newbrush );
	return newbrush;
} //end of the function TryMergeBrushes
//===========================================================================
//
// Parameter:				-
// Returns:					-
// Changes Globals:		-
//===========================================================================
bspbrush_t *MergeBrushes( bspbrush_t *brushlist ) {
	int nummerges, merged;
	bspbrush_t *b1, *b2, *tail, *newbrush, *newbrushlist;
	bspbrush_t *lastb2;

	if ( !brushlist ) {
		return NULL;
	}

	qprintf( "%5d brushes merged", nummerges = 0 );
	do
	{
		for ( tail = brushlist; tail; tail = tail->next )
		{
			if ( !tail->next ) {
				break;
			}
		} //end for
		merged = 0;
		newbrushlist = NULL;
		for ( b1 = brushlist; b1; b1 = brushlist )
		{
			lastb2 = b1;
			for ( b2 = b1->next; b2; b2 = b2->next )
			{
				//if the brushes don't have the same contents
				if ( b1->original->contents != b2->original->contents ||
					 b1->original->expansionbbox != b2->original->expansionbbox ) {
					newbrush = NULL;
				} else { newbrush = TryMergeBrushes( b1, b2 );}
				if ( newbrush ) {
					tail->next = newbrush;
					lastb2->next = b2->next;
					brushlist = brushlist->next;
					FreeBrush( b1 );
					FreeBrush( b2 );
					for ( tail = brushlist; tail; tail = tail->next )
					{
						if ( !tail->next ) {
							break;
						}
					} //end for
					merged++;
					qprintf( "\r%5d", nummerges++ );
					break;
				} //end if
				lastb2 = b2;
			} //end for
			  //if b1 can't be merged with any of the other brushes
			if ( !b2 ) {
				brushlist = brushlist->next;
				//keep b1
				b1->next = newbrushlist;
				newbrushlist = b1;
			} //end else
		} //end for
		brushlist = newbrushlist;
	} while ( merged );
	qprintf( "\n" );
	return newbrushlist;
} //end of the function MergeBrushes
//===========================================================================
//
// Parameter:				-
// Returns:					-
// Changes Globals:		-
//===========================================================================
void SplitBrush2( bspbrush_t *brush, int planenum,
				  bspbrush_t **front, bspbrush_t **back ) {
	SplitBrush( brush, planenum, front, back );
#if 0
	if ( *front && ( *front )->sides[( *front )->numsides - 1].texinfo == -1 ) {
		( *front )->sides[( *front )->numsides - 1].texinfo = ( *front )->sides[0].texinfo; // not -1
	}
	if ( *back && ( *back )->sides[( *back )->numsides - 1].texinfo == -1 ) {
		( *back )->sides[( *back )->numsides - 1].texinfo = ( *back )->sides[0].texinfo;    // not -1
	}
#endif
} //end of the function SplitBrush2
//===========================================================================
// Returns a list of brushes that remain after B is subtracted from A.
// May by empty if A is contained inside B.
// The originals are undisturbed.
//
// Parameter:				-
// Returns:					-
// Changes Globals:		-
//===========================================================================
bspbrush_t *SubtractBrush( bspbrush_t *a, bspbrush_t *b ) { // a - b = out (list)
	int i;
	bspbrush_t  *front, *back;
	bspbrush_t  *out, *in;

	in = a;
	out = NULL;
	for ( i = 0; i < b->numsides && in; i++ )
	{
		SplitBrush2( in, b->sides[i].planenum, &front, &back );
		if ( in != a ) {
			FreeBrush( in );
		}
		if ( front ) { // add to list
			front->next = out;
			out = front;
		} //end if
		in = back;
	} //end for
	if ( in ) {
		FreeBrush( in );
	} //end if
	else
	{   // didn't really intersect
		FreeBrushList( out );
		return a;
	} //end else
	return out;
} //end of the function SubtractBrush
//===========================================================================
// Returns a single brush made up by the intersection of the
// two provided brushes, or NULL if they are disjoint.
//
// The originals are undisturbed.
//
// Parameter:				-
// Returns:					-
// Changes Globals:		-
//===========================================================================
bspbrush_t *IntersectBrush( bspbrush_t *a, bspbrush_t *b ) {
	int i;
	bspbrush_t  *front, *back;
	bspbrush_t  *in;

	in = a;
	for ( i = 0 ; i < b->numsides && in ; i++ )
	{
		SplitBrush2( in, b->sides[i].planenum, &front, &back );
		if ( in != a ) {
			FreeBrush( in );
		}
		if ( front ) {
			FreeBrush( front );
		}
		in = back;
	} //end for

	if ( in == a ) {
		return NULL;
	}

	in->next = NULL;
	return in;
} //end of the function IntersectBrush
//===========================================================================
// Returns true if the two brushes definately do not intersect.
// There will be false negatives for some non-axial combinations.
//
// Parameter:				-
// Returns:					-
// Changes Globals:		-
//===========================================================================
qboolean BrushesDisjoint( bspbrush_t *a, bspbrush_t *b ) {
	int i, j;

	// check bounding boxes
	for ( i = 0 ; i < 3 ; i++ )
		if ( a->mins[i] >= b->maxs[i]
			 || a->maxs[i] <= b->mins[i] ) {
			return true;
		}                   // bounding boxes don't overlap

	// check for opposing planes
	for ( i = 0 ; i < a->numsides ; i++ )
	{
		for ( j = 0 ; j < b->numsides ; j++ )
		{
			if ( a->sides[i].planenum ==
				 ( b->sides[j].planenum ^ 1 ) ) {
				return true;    // opposite planes, so not touching
			}
		}
	}

	return false;   // might intersect
} //end of the function BrushesDisjoint
//===========================================================================
// Returns a content word for the intersection of two brushes.
// Some combinations will generate a combination (water + clip),
// but most will be the stronger of the two contents.
//
// Parameter:				-
// Returns:					-
// Changes Globals:		-
//===========================================================================
int IntersectionContents( int c1, int c2 ) {
	int out;

	out = c1 | c2;

	if ( out & CONTENTS_SOLID ) {
		out = CONTENTS_SOLID;
	}

	return out;
} //end of the function IntersectionContents
//===========================================================================
// Any planes shared with the box edge will be set to no texinfo
//
// Parameter:				-
// Returns:					-
// Changes Globals:		-
//===========================================================================
bspbrush_t *ClipBrushToBox( bspbrush_t *brush, vec3_t clipmins, vec3_t clipmaxs ) {
	int i, j;
	bspbrush_t  *front, *back;
	int p;

	for ( j = 0 ; j < 2 ; j++ )
	{
		if ( brush->maxs[j] > clipmaxs[j] ) {
			SplitBrush( brush, maxplanenums[j], &front, &back );
			if ( front ) {
				FreeBrush( front );
			}
			brush = back;
			if ( !brush ) {
				return NULL;
			}
		}
		if ( brush->mins[j] < clipmins[j] ) {
			SplitBrush( brush, minplanenums[j], &front, &back );
			if ( back ) {
				FreeBrush( back );
			}
			brush = front;
			if ( !brush ) {
				return NULL;
			}
		}
	}

	// remove any colinear faces

	for ( i = 0 ; i < brush->numsides ; i++ )
	{
		p = brush->sides[i].planenum & ~1;
		if ( p == maxplanenums[0] || p == maxplanenums[1]
			 || p == minplanenums[0] || p == minplanenums[1] ) {
			brush->sides[i].texinfo = TEXINFO_NODE;
			brush->sides[i].flags &= ~SFL_VISIBLE;
		}
	}
	return brush;
} //end of the function ClipBrushToBox
//===========================================================================
//
// Parameter:				-
// Returns:					-
// Changes Globals:		-
//===========================================================================
bspbrush_t *MakeBspBrushList( int startbrush, int endbrush,
							  vec3_t clipmins, vec3_t clipmaxs ) {
	mapbrush_t  *mb;
	bspbrush_t  *brushlist, *newbrush;
	int i, j;
	int c_faces;
	int c_brushes;
	int numsides;
	int vis;
	vec3_t normal;
	float dist;

	for ( i = 0 ; i < 2 ; i++ )
	{
		VectorClear( normal );
		normal[i] = 1;
		dist = clipmaxs[i];
		maxplanenums[i] = FindFloatPlane( normal, dist );
		dist = clipmins[i];
		minplanenums[i] = FindFloatPlane( normal, dist );
	}

	brushlist = NULL;
	c_faces = 0;
	c_brushes = 0;

	for ( i = startbrush ; i < endbrush ; i++ )
	{
		mb = &mapbrushes[i];

		numsides = mb->numsides;
		if ( !numsides ) {
			continue;
		}

		// make sure the brush has at least one face showing
		vis = 0;
		for ( j = 0 ; j < numsides ; j++ )
			if ( ( mb->original_sides[j].flags & SFL_VISIBLE ) && mb->original_sides[j].winding ) {
				vis++;
			}
#if 0
		if ( !vis ) {
			continue;   // no faces at all
		}
#endif
		// if the brush is outside the clip area, skip it
		for ( j = 0 ; j < 3 ; j++ )
			if ( mb->mins[j] >= clipmaxs[j]
				 || mb->maxs[j] <= clipmins[j] ) {
				break;
			}
		if ( j != 3 ) {
			continue;
		}

		//
		// make a copy of the brush
		//
		newbrush = AllocBrush( mb->numsides );
		newbrush->original = mb;
		newbrush->numsides = mb->numsides;
		memcpy( newbrush->sides, mb->original_sides, numsides * sizeof( side_t ) );
		for ( j = 0 ; j < numsides ; j++ )
		{
			if ( newbrush->sides[j].winding ) {
				newbrush->sides[j].winding = CopyWinding( newbrush->sides[j].winding );
			}
			if ( newbrush->sides[j].surf & SURF_HINT ) {
				newbrush->sides[j].flags |= SFL_VISIBLE;    // hints are always visible
			}
		}
		VectorCopy( mb->mins, newbrush->mins );
		VectorCopy( mb->maxs, newbrush->maxs );

		//
		// carve off anything outside the clip box
		//
		newbrush = ClipBrushToBox( newbrush, clipmins, clipmaxs );
		if ( !newbrush ) {
			continue;
		}

		c_faces += vis;
		c_brushes++;

		newbrush->next = brushlist;
		brushlist = newbrush;
	}

	return brushlist;
} //end of the function MakeBspBrushList
//===========================================================================
//
// Parameter:				-
// Returns:					-
// Changes Globals:		-
//===========================================================================
bspbrush_t *AddBrushListToTail( bspbrush_t *list, bspbrush_t *tail ) {
	bspbrush_t  *walk, *next;

	for ( walk = list ; walk ; walk = next )
	{   // add to end of list
		next = walk->next;
		walk->next = NULL;
		tail->next = walk;
		tail = walk;
	} //end for
	return tail;
} //end of the function AddBrushListToTail
//===========================================================================
// Builds a new list that doesn't hold the given brush
//
// Parameter:				-
// Returns:					-
// Changes Globals:		-
//===========================================================================
bspbrush_t *CullList( bspbrush_t *list, bspbrush_t *skip1 ) {
	bspbrush_t  *newlist;
	bspbrush_t  *next;

	newlist = NULL;

	for ( ; list ; list = next )
	{
		next = list->next;
		if ( list == skip1 ) {
			FreeBrush( list );
			continue;
		}
		list->next = newlist;
		newlist = list;
	}
	return newlist;
} //end of the function CullList
//===========================================================================
//
// Parameter:				-
// Returns:					-
// Changes Globals:		-
//===========================================================================
/*
void WriteBrushMap(char *name, bspbrush_t *list)
{
	FILE	*f;
	side_t	*s;
	int		i;
	winding_t	*w;

	Log_Print("writing %s\n", name);
	f = fopen (name, "wb");
	if (!f)
		Error ("Can't write %s\b", name);

	fprintf (f, "{\n\"classname\" \"worldspawn\"\n");

	for ( ; list ; list=list->next )
	{
		fprintf (f, "{\n");
		for (i=0,s=list->sides ; i<list->numsides ; i++,s++)
		{
			w = BaseWindingForPlane (mapplanes[s->planenum].normal, mapplanes[s->planenum].dist);

			fprintf (f,"( %i %i %i ) ", (int)w->p[0][0], (int)w->p[0][1], (int)w->p[0][2]);
			fprintf (f,"( %i %i %i ) ", (int)w->p[1][0], (int)w->p[1][1], (int)w->p[1][2]);
			fprintf (f,"( %i %i %i ) ", (int)w->p[2][0], (int)w->p[2][1], (int)w->p[2][2]);

			fprintf (f, "%s 0 0 0 1 1\n", texinfo[s->texinfo].texture);
			FreeWinding (w);
		}
		fprintf (f, "}\n");
	}
	fprintf (f, "}\n");

	fclose (f);
} //end of the function WriteBrushMap
*/
//===========================================================================
// Returns true if b1 is allowed to bite b2
//
// Parameter:				-
// Returns:					-
// Changes Globals:		-
//===========================================================================
qboolean BrushGE( bspbrush_t *b1, bspbrush_t *b2 ) {
#ifdef ME
	if ( create_aas ) {
		if ( b1->original->expansionbbox != b2->original->expansionbbox ) {
			return false;
		} //end if
		  //never have something else bite a ladder brush
		  //never have a ladder brush bite something else
		if ( ( b1->original->contents & CONTENTS_LADDER )
			 && !( b2->original->contents & CONTENTS_LADDER ) ) {
			return false;
		} //end if
	} //end if
#endif //ME
	   // detail brushes never bite structural brushes
	if ( ( b1->original->contents & CONTENTS_DETAIL )
		 && !( b2->original->contents & CONTENTS_DETAIL ) ) {
		return false;
	} //end if
	if ( b1->original->contents & CONTENTS_SOLID ) {
		return true;
	} //end if
	return false;
} //end of the function BrushGE
//===========================================================================
// Carves any intersecting solid brushes into the minimum number
// of non-intersecting brushes.
//
// Parameter:				-
// Returns:					-
// Changes Globals:		-
//===========================================================================
bspbrush_t *ChopBrushes( bspbrush_t *head ) {
	bspbrush_t  *b1, *b2, *next;
	bspbrush_t  *tail;
	bspbrush_t  *keep;
	bspbrush_t  *sub, *sub2;
	int c1, c2;
	int num_csg_iterations;

	Log_Print( "-------- Brush CSG ---------\n" );
	Log_Print( "%6d original brushes\n", CountBrushList( head ) );

	num_csg_iterations = 0;
	qprintf( "%6d output brushes", num_csg_iterations );

#if 0
	if ( startbrush == 0 ) {
		WriteBrushList( "before.gl", head, false );
	}
#endif
	keep = NULL;

newlist:
	// find tail
	if ( !head ) {
		return NULL;
	}

	for ( tail = head; tail->next; tail = tail->next )
		;

	for ( b1 = head ; b1 ; b1 = next )
	{
		next = b1->next;

		//if the conversion is cancelled
		if ( cancelconversion ) {
			b1->next = keep;
			keep = b1;
			continue;
		} //end if

		for ( b2 = b1->next; b2; b2 = b2->next )
		{
			if ( BrushesDisjoint( b1, b2 ) ) {
				continue;
			}

			sub = NULL;
			sub2 = NULL;
			c1 = 999999;
			c2 = 999999;

			if ( BrushGE( b2, b1 ) ) {
				sub = SubtractBrush( b1, b2 );
				if ( sub == b1 ) {
					continue;       // didn't really intersect
				} //end if
				if ( !sub ) { // b1 is swallowed by b2
					head = CullList( b1, b1 );
					goto newlist;
				}
				c1 = CountBrushList( sub );
			}

			if ( BrushGE( b1, b2 ) ) {
				sub2 = SubtractBrush( b2, b1 );
				if ( sub2 == b2 ) {
					continue;       // didn't really intersect
				}
				if ( !sub2 ) { // b2 is swallowed by b1
					FreeBrushList( sub );
					head = CullList( b1, b2 );
					goto newlist;
				}
				c2 = CountBrushList( sub2 );
			}

			if ( !sub && !sub2 ) {
				continue;       // neither one can bite

			}
			// only accept if it didn't fragment
			// (commenting this out allows full fragmentation)
			if ( c1 > 1 && c2 > 1 ) {
				if ( sub2 ) {
					FreeBrushList( sub2 );
				}
				if ( sub ) {
					FreeBrushList( sub );
				}
				continue;
			}

			if ( c1 < c2 ) {
				if ( sub2 ) {
					FreeBrushList( sub2 );
				}
				tail = AddBrushListToTail( sub, tail );
				head = CullList( b1, b1 );
				goto newlist;
			} //end if
			else
			{
				if ( sub ) {
					FreeBrushList( sub );
				}
				tail = AddBrushListToTail( sub2, tail );
				head = CullList( b1, b2 );
				goto newlist;
			} //end else
		} //end for

		if ( !b2 ) { // b1 is no longer intersecting anything, so keep it
			b1->next = keep;
			keep = b1;
		} //end if
		num_csg_iterations++;
		qprintf( "\r%6d", num_csg_iterations );
	} //end for

	if ( cancelconversion ) {
		return keep;
	}
	//
	qprintf( "\n" );
	Log_Write( "%6d output brushes\r\n", num_csg_iterations );

#if 0
	{
		WriteBrushList( "after.gl", keep, false );
		WriteBrushMap( "after.map", keep );
	}
#endif

	return keep;
} //end of the function ChopBrushes
//===========================================================================
//
// Parameter:				-
// Returns:					-
// Changes Globals:		-
//===========================================================================
bspbrush_t *InitialBrushList( bspbrush_t *list ) {
	bspbrush_t *b;
	bspbrush_t  *out, *newb;
	int i;

	// only return brushes that have visible faces
	out = NULL;
	for ( b = list ; b ; b = b->next )
	{
#if 0
		for ( i = 0 ; i < b->numsides ; i++ )
			if ( b->sides[i].flags & SFL_VISIBLE ) {
				break;
			}
		if ( i == b->numsides ) {
			continue;
		}
#endif
		newb = CopyBrush( b );
		newb->next = out;
		out = newb;

		// clear visible, so it must be set by MarkVisibleFaces_r
		// to be used in the optimized list
		for ( i = 0 ; i < b->numsides ; i++ )
		{
			newb->sides[i].original = &b->sides[i];
//			newb->sides[i].visible = true;
			b->sides[i].flags &= ~SFL_VISIBLE;
		}
	}

	return out;
} //end of the function InitialBrushList
//===========================================================================
//
// Parameter:				-
// Returns:					-
// Changes Globals:		-
//===========================================================================
bspbrush_t *OptimizedBrushList( bspbrush_t *list ) {
	bspbrush_t *b;
	bspbrush_t  *out, *newb;
	int i;

	// only return brushes that have visible faces
	out = NULL;
	for ( b = list ; b ; b = b->next )
	{
		for ( i = 0 ; i < b->numsides ; i++ )
			if ( b->sides[i].flags & SFL_VISIBLE ) {
				break;
			}
		if ( i == b->numsides ) {
			continue;
		}
		newb = CopyBrush( b );
		newb->next = out;
		out = newb;
	} //end for

//	WriteBrushList ("vis.gl", out, true);
	return out;
} //end of the function OptimizeBrushList
//===========================================================================
//
// Parameter:				-
// Returns:					-
// Changes Globals:		-
//===========================================================================
tree_t *ProcessWorldBrushes( int brush_start, int brush_end ) {
	bspbrush_t *brushes;
	tree_t *tree;
	node_t *node;
	vec3_t mins, maxs;

	//take the whole world
	mins[0] = map_mins[0] - 8;
	mins[1] = map_mins[1] - 8;
	mins[2] = map_mins[2] - 8;

	maxs[0] = map_maxs[0] + 8;
	maxs[1] = map_maxs[1] + 8;
	maxs[2] = map_maxs[2] + 8;

	//reset the brush bsp
	ResetBrushBSP();

	// the makelist and chopbrushes could be cached between the passes...

	//create a list with brushes that are within the given mins/maxs
	//some brushes will be cut and only the part that falls within the
	//mins/maxs will be in the bush list
	brushes = MakeBspBrushList( brush_start, brush_end, mins, maxs );
	//

	if ( !brushes ) {
		node = AllocNode();
		node->planenum = PLANENUM_LEAF;
		node->contents = CONTENTS_SOLID;

		tree = Tree_Alloc();
		tree->headnode = node;
		VectorCopy( mins, tree->mins );
		VectorCopy( maxs, tree->maxs );
	} //end if
	else
	{
		//Carves any intersecting solid brushes into the minimum number
		//of non-intersecting brushes.
		if ( !nocsg ) {
			brushes = ChopBrushes( brushes );
			/*
			if (create_aas)
			{
				brushes = MergeBrushes(brushes);
			} //end if*/
		} //end if
		  //if the conversion is cancelled
		if ( cancelconversion ) {
			FreeBrushList( brushes );
			return NULL;
		} //end if
		  //create the actual bsp tree
		tree = BrushBSP( brushes, mins, maxs );
	} //end else
	  //return the tree
	return tree;
} //end of the function ProcessWorldBrushes