gtkradiant/tools/quake3/q3map2/brush.c

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

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."

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



/* marker */
#define BRUSH_C



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



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

functions

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

/*
AllocSideRef() - ydnar
allocates and assigns a brush side reference
*/

sideRef_t *AllocSideRef( side_t *side, sideRef_t *next )
{
	sideRef_t *sideRef;
	
	
	/* dummy check */
	if( side == NULL )
		return next;
	
	/* allocate and return */
	sideRef = safe_malloc( sizeof( *sideRef ) );
	sideRef->side = side;
	sideRef->next = next;
	return sideRef;
}



/*
CountBrushList()
counts the number of brushes in a brush linked list
*/

int	CountBrushList( brush_t *brushes )
{
	int	c = 0;
	
	
	/* count brushes */
	for( ; brushes != NULL; brushes = brushes->next )
		c++;
	return c;
}



/*
AllocBrush()
allocates a new brush
*/

brush_t *AllocBrush( int numSides )
{
	brush_t		*bb;
	size_t		c;
	
	
	/* allocate and clear */
	if( numSides <= 0 )
		Error( "AllocBrush called with numsides = %d", numSides );
	c = (size_t)&(((brush_t*) 0)->sides[ numSides ]);
	bb = safe_malloc( c );
	memset( bb, 0, c );
	if( numthreads == 1 )
		numActiveBrushes++;
	
	/* return it */
	return bb;
}



/*
FreeBrush()
frees a single brush and all sides/windings
*/

void FreeBrush( brush_t *b )
{
	int			i;
	
	
	/* error check */
	if( *((unsigned int*) b) == 0xFEFEFEFE )
	{
		Sys_FPrintf( SYS_VRB, "WARNING: Attempt to free an already freed brush!\n" );
		return;
	}
	
	/* free brush sides */
	for( i = 0; i < b->numsides; i++ )
		if( b->sides[i].winding != NULL )
			FreeWinding( b->sides[ i ].winding );
	
	/* ydnar: overwrite it */
	memset( b, 0xFE, (size_t)&(((brush_t*) 0)->sides[ b->numsides ]) );
	*((unsigned int*) b) = 0xFEFEFEFE;
	
	/* free it */
	free( b );
	if( numthreads == 1 )
		numActiveBrushes--;
}



/*
FreeBrushList()
frees a linked list of brushes
*/

void FreeBrushList( brush_t *brushes )
{
	brush_t		*next;
	
	
	/* walk brush list */
	for( ; brushes != NULL; brushes = next )
	{
		next = brushes->next;
		FreeBrush( brushes );
	}		
}



/*
CopyBrush()
duplicates the brush, sides, and windings
*/

brush_t *CopyBrush( brush_t *brush )
{
	brush_t		*newBrush;
	size_t		size;
	int			i;
	
	
	/* copy brush */
	size = (size_t)&(((brush_t*) 0)->sides[ brush->numsides ]);
	newBrush = AllocBrush( brush->numsides );
	memcpy( newBrush, brush, size );
	
	/* ydnar: nuke linked list */
	newBrush->next = NULL;
	
	/* copy sides */
	for( i = 0; i < brush->numsides; i++ )
	{
		if( brush->sides[ i ].winding != NULL )
			newBrush->sides[ i ].winding = CopyWinding( brush->sides[ i ].winding );
	}
	
	/* return it */
	return newBrush;
}




/*
BoundBrush()
sets the mins/maxs based on the windings
returns false if the brush doesn't enclose a valid volume
*/

qboolean BoundBrush( brush_t *brush )
{
	int			i, j;
	winding_t	*w;
	
	
	ClearBounds( brush->mins, brush->maxs );
	for( i = 0; i < brush->numsides; i++ )
	{
		w = brush->sides[ i ].winding;
		if( w == NULL )
			continue;
		for( j = 0; j < w->numpoints; j++ )
			AddPointToBounds( w->p[ j ], brush->mins, brush->maxs );
	}
	
	for( i = 0; i < 3; i++ )
	{
		if( brush->mins[ i ] < MIN_WORLD_COORD || brush->maxs[ i ] > MAX_WORLD_COORD || brush->mins[i] >= brush->maxs[ i ] )
			return qfalse;
	}
	
	return qtrue;
}




/*
SnapWeldVector() - ydnar
welds two vec3_t's into a third, taking into account nearest-to-integer
instead of averaging
*/

#define SNAP_EPSILON	0.01

void SnapWeldVector( vec3_t a, vec3_t b, vec3_t out )
{
	int		i;
	vec_t	ai, bi, outi;
	
	
	/* dummy check */
	if( a == NULL || b == NULL || out == NULL )
		return;
	
	/* do each element */
	for( i = 0; i < 3; i++ )
	{
		/* round to integer */
		ai = Q_rint( a[ i ] );
		bi = Q_rint( a[ i ] );
		
		/* prefer exact integer */
		if( ai == a[ i ] )
			out[ i ] = a[ i ];
		else if( bi == b[ i ] )
			out[ i ] = b[ i ];

		/* use nearest */
		else if( fabs( ai - a[ i ] ) < fabs( bi < b[ i ] ) )
			out[ i ] = a[ i ];
		else
			out[ i ] = b[ i ];
		
		/* snap */
		outi = Q_rint( out[ i ] );
		if( fabs( outi - out[ i ] ) <= SNAP_EPSILON )
			out[ i ] = outi;
	}
}

/*
==================
SnapWeldVectorAccu

Welds two vectors into a third, taking into account nearest-to-integer
instead of averaging.
==================
*/
void SnapWeldVectorAccu(vec3_accu_t a, vec3_accu_t b, vec3_accu_t out)
{
	// I'm just preserving what I think was the intended logic of the original
	// SnapWeldVector().  I'm not actually sure where this function should even
	// be used.  I'd like to know which kinds of problems this function addresses.

	// TODO: I thought we're snapping all coordinates to nearest 1/8 unit?
	// So what is natural about snapping to the nearest integer?  Maybe we should
	// be snapping to the nearest 1/8 unit instead?

	int		i;
	vec_accu_t	ai, bi, ad, bd;
	
	if (a == NULL || b == NULL || out == NULL)
		Error("SnapWeldVectorAccu: NULL argument");
	
	for (i = 0; i < 3; i++)
	{
		ai = Q_rintAccu(a[i]);
		bi = Q_rintAccu(b[i]);
		ad = fabs(ai - a[i]);
		bd = fabs(bi - b[i]);
	
		if (ad < bd)
		{
			if (ad < SNAP_EPSILON)	out[i] = ai;
			else			out[i] = a[i];
		}
		else
		{
			if (bd < SNAP_EPSILON)	out[i] = bi;
			else			out[i] = b[i];
		}
	}
}



/*
FixWinding() - ydnar
removes degenerate edges from a winding
returns qtrue if the winding is valid
*/

#define DEGENERATE_EPSILON	0.1

qboolean FixWinding( winding_t *w )
{
	qboolean	valid = qtrue;
	int			i, j, k;
	vec3_t		vec;
	float		dist;
	
	
	/* dummy check */
	if( !w )
		return qfalse;
	
	/* check all verts */
	for( i = 0; i < w->numpoints; i++ )
	{
		/* don't remove points if winding is a triangle */
		if( w->numpoints == 3 )
			return valid;
		
		/* get second point index */
		j = (i + 1) % w->numpoints;
		
		/* degenerate edge? */
		VectorSubtract( w->p[ i ], w->p[ j ], vec );
		dist = VectorLength( vec );
		if( dist < DEGENERATE_EPSILON )
		{
			valid = qfalse;
			//Sys_FPrintf( SYS_VRB, "WARNING: Degenerate winding edge found, fixing...\n" );
			
			/* create an average point (ydnar 2002-01-26: using nearest-integer weld preference) */
			SnapWeldVector( w->p[ i ], w->p[ j ], vec );
			VectorCopy( vec, w->p[ i ] );
			//VectorAdd( w->p[ i ], w->p[ j ], vec );
			//VectorScale( vec, 0.5, w->p[ i ] );
			
			/* move the remaining verts */
			for( k = i + 2; k < w->numpoints; k++ )
			{
				VectorCopy( w->p[ k ], w->p[ k - 1 ] );
			}
			w->numpoints--;
		}
	}
	
	/* one last check and return */
	if( w->numpoints < 3 )
		valid = qfalse;
	return valid;
}

/*
==================
FixWindingAccu

Removes degenerate edges (edges that are too short) from a winding.
Returns qtrue if the winding has been altered by this function.
Returns qfalse if the winding is untouched by this function.

It's advised that you check the winding after this function exits to make
sure it still has at least 3 points.  If that is not the case, the winding
cannot be considered valid.  The winding may degenerate to one or two points
if the some of the winding's points are close together.
==================
*/
qboolean FixWindingAccu(winding_accu_t *w)
{
	int		i, j, k;
	vec3_accu_t	vec;
	vec_accu_t	dist;
	qboolean	done, altered;

	if (w == NULL) Error("FixWindingAccu: NULL argument");

	altered = qfalse;

	while (qtrue)
	{
		if (w->numpoints < 2) break; // Don't remove the only remaining point.
		done = qtrue;
		for (i = 0; i < w->numpoints; i++)
		{
			j = (((i + 1) == w->numpoints) ? 0 : (i + 1));

			VectorSubtractAccu(w->p[i], w->p[j], vec);
			dist = VectorLengthAccu(vec);
			if (dist < DEGENERATE_EPSILON)
			{
				// TODO: I think the "snap weld vector" was written before
				// some of the math precision fixes, and its purpose was
				// probably to address math accuracy issues.  We can think
				// about changing the logic here.  Maybe once plane distance
				// gets 64 bits, we can look at it then.
				SnapWeldVectorAccu(w->p[i], w->p[j], vec);
				VectorCopyAccu(vec, w->p[i]);
				for (k = j + 1; k < w->numpoints; k++)
				{
					VectorCopyAccu(w->p[k], w->p[k - 1]);
				}
				w->numpoints--;
				altered = qtrue;
				// The only way to finish off fixing the winding consistently and
				// accurately is by fixing the winding all over again.  For example,
				// the point at index i and the point at index i-1 could now be
				// less than the epsilon distance apart.  There are too many special
				// case problems we'd need to handle if we didn't start from the
				// beginning.
				done = qfalse;
				break; // This will cause us to return to the "while" loop.
			}
		}
		if (done) break;
	}

	return altered;
}


/*
CreateBrushWindings()
makes basewindigs for sides and mins/maxs for the brush
returns false if the brush doesn't enclose a valid volume
*/

qboolean CreateBrushWindings( brush_t *brush )
{
	int			i, j;
#if EXPERIMENTAL_HIGH_PRECISION_MATH_Q3MAP2_FIXES
	winding_accu_t	*w;
#else
	winding_t	*w;
#endif
	side_t		*side;
	plane_t		*plane;
	
	
	/* walk the list of brush sides */
	for( i = 0; i < brush->numsides; i++ )
	{
		/* get side and plane */
		side = &brush->sides[ i ];
		plane = &mapplanes[ side->planenum ];
		
		/* make huge winding */
#if EXPERIMENTAL_HIGH_PRECISION_MATH_Q3MAP2_FIXES
		w = BaseWindingForPlaneAccu(plane->normal, plane->dist);
#else
		w = BaseWindingForPlane( plane->normal, plane->dist );
#endif
		
		/* walk the list of brush sides */
		for( j = 0; j < brush->numsides && w != NULL; j++ )
		{
			if( i == j )
				continue;
			if( brush->sides[ j ].planenum == (brush->sides[ i ].planenum ^ 1) )
				continue;		/* back side clipaway */
			if( brush->sides[ j ].bevel )
				continue;
			plane = &mapplanes[ brush->sides[ j ].planenum ^ 1 ];
#if EXPERIMENTAL_HIGH_PRECISION_MATH_Q3MAP2_FIXES
			ChopWindingInPlaceAccu(&w, plane->normal, plane->dist, 0);
#else
			ChopWindingInPlace( &w, plane->normal, plane->dist, 0 ); // CLIP_EPSILON );
#endif
			
			/* ydnar: fix broken windings that would generate trifans */
#if EXPERIMENTAL_HIGH_PRECISION_MATH_Q3MAP2_FIXES
			// I think it's better to FixWindingAccu() once after we chop with all planes
			// so that error isn't multiplied.  There is nothing natural about welding
			// the points unless they are the final endpoints.  ChopWindingInPlaceAccu()
			// is able to handle all kinds of degenerate windings.
#else
			FixWinding( w );
#endif
		}
		
		/* set side winding */
#if EXPERIMENTAL_HIGH_PRECISION_MATH_Q3MAP2_FIXES
		if (w != NULL)
		{
			FixWindingAccu(w);
			if (w->numpoints < 3)
			{
				FreeWindingAccu(w);
				w = NULL;
			}
		}
		side->winding = (w ? CopyWindingAccuToRegular(w) : NULL);
		if (w) FreeWindingAccu(w);
#else
		side->winding = w;
#endif
	}
	
	/* find brush bounds */
	return BoundBrush( brush );
}




/*
==================
BrushFromBounds

Creates a new axial brush
==================
*/
brush_t	*BrushFromBounds (vec3_t mins, vec3_t maxs)
{
	brush_t		*b;
	int			i;
	vec3_t		normal;
	vec_t		dist;

	b = AllocBrush (6);
	b->numsides = 6;
	for (i=0 ; i<3 ; i++)
	{
		VectorClear (normal);
		normal[i] = 1;
		dist = maxs[i];
		b->sides[i].planenum = FindFloatPlane (normal, dist, 1, (vec3_t*) &maxs );

		normal[i] = -1;
		dist = -mins[i];
		b->sides[3+i].planenum = FindFloatPlane (normal, dist, 1, (vec3_t*) &mins );
	}

	CreateBrushWindings (b);

	return b;
}

/*
==================
BrushVolume

==================
*/
vec_t BrushVolume (brush_t *brush)
{
	int			i;
	winding_t	*w;
	vec3_t		corner;
	vec_t		d, area, volume;
	plane_t		*plane;

	if (!brush)
		return 0;

	// grab the first valid point as the corner

	w = NULL;
	for (i=0 ; i<brush->numsides ; i++)
	{
		w = brush->sides[i].winding;
		if (w)
			break;
	}
	if (!w)
		return 0;
	VectorCopy (w->p[0], corner);

	// make tetrahedrons to all other faces

	volume = 0;
	for ( ; i<brush->numsides ; i++)
	{
		w = brush->sides[i].winding;
		if (!w)
			continue;
		plane = &mapplanes[brush->sides[i].planenum];
		d = -(DotProduct (corner, plane->normal) - plane->dist);
		area = WindingArea (w);
		volume += d*area;
	}

	volume /= 3;
	return volume;
}



/*
WriteBSPBrushMap()
writes a map with the split bsp brushes
*/

void WriteBSPBrushMap( char *name, brush_t *list )
{
	FILE		*f;
	side_t		*s;
	int			i;
	winding_t	*w;
	
	
	/* note it */
	Sys_Printf( "Writing %s\n", name );
	
	/* open the map file */
	f = fopen( name, "wb" );
	if( f == NULL )
		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++)
		{
			// TODO: See if we can use a smaller winding to prevent resolution loss.
			// Is WriteBSPBrushMap() used only to decompile maps?
			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, "notexture 0 0 0 1 1\n" );
			FreeWinding (w);
		}
		fprintf (f, "}\n");
	}
	fprintf (f, "}\n");

	fclose (f);

}



/*
FilterBrushIntoTree_r()
adds brush reference to any intersecting bsp leafnode
*/

int FilterBrushIntoTree_r( brush_t *b, node_t *node )
{
	brush_t		*front, *back;
	int			c;
	
	
	/* dummy check */
	if( b == NULL )
		return 0;
	
	/* add it to the leaf list */
	if( node->planenum == PLANENUM_LEAF )
	{
		/* something somewhere is hammering brushlist */
		b->next = node->brushlist;
		node->brushlist = b;
		
		/* classify the leaf by the structural brush */
		if( !b->detail )
		{
			if( b->opaque )
			{
				node->opaque = qtrue;
				node->areaportal = qfalse;
			}
			else if( b->compileFlags & C_AREAPORTAL )
			{
				if( !node->opaque )
					node->areaportal = qtrue;
			}
		}
		
		return 1;
	}
	
	/* split it by the node plane */
	c = b->numsides;
	SplitBrush( b, node->planenum, &front, &back );
	FreeBrush( b );
	
	c = 0;
	c += FilterBrushIntoTree_r( front, node->children[ 0 ] );
	c += FilterBrushIntoTree_r( back, node->children[ 1 ] );
	
	return c;
}



/*
FilterDetailBrushesIntoTree
fragment all the detail brushes into the structural leafs
*/

void FilterDetailBrushesIntoTree( entity_t *e, tree_t *tree )
{
	brush_t				*b, *newb;
	int					r;
	int					c_unique, c_clusters;
	int					i;
	
	
	/* note it */
	Sys_FPrintf( SYS_VRB,  "--- FilterDetailBrushesIntoTree ---\n" );
	
	/* walk the list of brushes */
	c_unique = 0;
	c_clusters = 0;
	for( b = e->brushes; b; b = b->next )
	{
		if( !b->detail )
			continue;
		c_unique++;
		newb = CopyBrush( b );
		r = FilterBrushIntoTree_r( newb, tree->headnode );
		c_clusters += r;
		
		/* mark all sides as visible so drawsurfs are created */
		if( r )
		{
			for( i = 0; i < b->numsides; i++ )
			{
				if( b->sides[ i ].winding )
					b->sides[ i ].visible = qtrue;
			}
		}
	}
	
	/* emit some statistics */
	Sys_FPrintf( SYS_VRB, "%9d detail brushes\n", c_unique );
	Sys_FPrintf( SYS_VRB, "%9d cluster references\n", c_clusters );
}

/*
=====================
FilterStructuralBrushesIntoTree

Mark the leafs as opaque and areaportals
=====================
*/
void FilterStructuralBrushesIntoTree( entity_t *e, tree_t *tree ) {
	brush_t			*b, *newb;
	int					r;
	int					c_unique, c_clusters;
	int					i;

	Sys_FPrintf (SYS_VRB, "--- FilterStructuralBrushesIntoTree ---\n");

	c_unique = 0;
	c_clusters = 0;
	for ( b = e->brushes ; b ; b = b->next ) {
		if ( b->detail ) {
			continue;
		}
		c_unique++;
		newb = CopyBrush( b );
		r = FilterBrushIntoTree_r( newb, tree->headnode );
		c_clusters += r;

		// mark all sides as visible so drawsurfs are created
		if ( r ) {
			for ( i = 0 ; i < b->numsides ; i++ ) {
				if ( b->sides[i].winding ) {
					b->sides[i].visible = qtrue;
				}
			}
		}
	}
	
	/* emit some statistics */
	Sys_FPrintf( SYS_VRB, "%9d structural brushes\n", c_unique );
	Sys_FPrintf( SYS_VRB, "%9d cluster references\n", c_clusters );
}



/*
================
AllocTree
================
*/
tree_t *AllocTree (void)
{
	tree_t	*tree;

	tree = safe_malloc(sizeof(*tree));
	memset (tree, 0, sizeof(*tree));
	ClearBounds (tree->mins, tree->maxs);

	return tree;
}

/*
================
AllocNode
================
*/
node_t *AllocNode (void)
{
	node_t	*node;

	node = safe_malloc(sizeof(*node));
	memset (node, 0, sizeof(*node));

	return node;
}


/*
================
WindingIsTiny

Returns true if the winding would be crunched out of
existance by the vertex snapping.
================
*/
#define	EDGE_LENGTH	0.2
qboolean WindingIsTiny (winding_t *w)
{
/*
	if (WindingArea (w) < 1)
		return qtrue;
	return qfalse;
*/
	int		i, j;
	vec_t	len;
	vec3_t	delta;
	int		edges;

	edges = 0;
	for (i=0 ; i<w->numpoints ; i++)
	{
		j = i == w->numpoints - 1 ? 0 : i+1;
		VectorSubtract (w->p[j], w->p[i], delta);
		len = VectorLength (delta);
		if (len > EDGE_LENGTH)
		{
			if (++edges == 3)
				return qfalse;
		}
	}
	return qtrue;
}

/*
================
WindingIsHuge

Returns true if the winding still has one of the points
from basewinding for plane
================
*/
qboolean WindingIsHuge (winding_t *w)
{
	int		i, j;

	for (i=0 ; i<w->numpoints ; i++)
	{
		for (j=0 ; j<3 ; j++)
			if (w->p[i][j] <= MIN_WORLD_COORD || w->p[i][j] >= MAX_WORLD_COORD)
				return qtrue;
	}
	return qfalse;
}

//============================================================

/*
==================
BrushMostlyOnSide

==================
*/
int BrushMostlyOnSide (brush_t *brush, plane_t *plane)
{
	int			i, j;
	winding_t	*w;
	vec_t		d, max;
	int			side;

	max = 0;
	side = PSIDE_FRONT;
	for (i=0 ; i<brush->numsides ; i++)
	{
		w = brush->sides[i].winding;
		if (!w)
			continue;
		for (j=0 ; j<w->numpoints ; j++)
		{
			d = DotProduct (w->p[j], plane->normal) - plane->dist;
			if (d > max)
			{
				max = d;
				side = PSIDE_FRONT;
			}
			if (-d > max)
			{
				max = -d;
				side = PSIDE_BACK;
			}
		}
	}
	return side;
}



/*
SplitBrush()
generates two new brushes, leaving the original unchanged
*/

void SplitBrush( brush_t *brush, int planenum, brush_t **front, brush_t **back )
{
	brush_t		*b[2];
	int			i, j;
	winding_t	*w, *cw[2], *midwinding;
	plane_t		*plane, *plane2;
	side_t		*s, *cs;
	float		d, d_front, d_back;
	
	
	*front = NULL;
	*back = NULL;
	plane = &mapplanes[planenum];
	
	// check all points
	d_front = d_back = 0;
	for (i=0 ; i<brush->numsides ; i++)
	{
		w = brush->sides[i].winding;
		if (!w)
			continue;
		for (j=0 ; j<w->numpoints ; j++)
		{
			d = DotProduct (w->p[j], plane->normal) - plane->dist;
			if (d > 0 && d > d_front)
				d_front = d;
			if (d < 0 && d < d_back)
				d_back = d;
		}
	}
	
	if (d_front < 0.1) // PLANESIDE_EPSILON)
	{	// only on back
		*back = CopyBrush( brush );
		return;
	}
	
	if (d_back > -0.1) // PLANESIDE_EPSILON)
	{	// only on front
		*front = CopyBrush( brush );
		return;
	}
	
	// create a new winding from the split plane
	w = BaseWindingForPlane (plane->normal, plane->dist);
	for (i=0 ; i<brush->numsides && w ; i++)
	{
		plane2 = &mapplanes[brush->sides[i].planenum ^ 1];
		ChopWindingInPlace (&w, plane2->normal, plane2->dist, 0); // PLANESIDE_EPSILON);
	}

	if (!w || WindingIsTiny (w) )
	{	// the brush isn't really split
		int		side;

		side = BrushMostlyOnSide (brush, plane);
		if (side == PSIDE_FRONT)
			*front = CopyBrush (brush);
		if (side == PSIDE_BACK)
			*back = CopyBrush (brush);
		return;
	}
	
	if( WindingIsHuge( w ) )
		Sys_FPrintf( SYS_VRB,"WARNING: huge winding\n" );

	midwinding = w;

	// split it for real

	for (i=0 ; i<2 ; i++)
	{
		b[i] = AllocBrush (brush->numsides+1);
		memcpy( b[i], brush, sizeof( brush_t ) - sizeof( brush->sides ) );
		b[i]->numsides = 0;
		b[i]->next = NULL;
		b[i]->original = brush->original;
	}

	// split all the current windings

	for (i=0 ; i<brush->numsides ; i++)
	{
		s = &brush->sides[i];
		w = s->winding;
		if (!w)
			continue;
		ClipWindingEpsilon (w, plane->normal, plane->dist,
			0 /*PLANESIDE_EPSILON*/, &cw[0], &cw[1]);
		for (j=0 ; j<2 ; j++)
		{
			if (!cw[j])
				continue;
			cs = &b[j]->sides[b[j]->numsides];
			b[j]->numsides++;
			*cs = *s;
			cs->winding = cw[j];
		}
	}


	// see if we have valid polygons on both sides
	for (i=0 ; i<2 ; i++)
	{
		if (b[i]->numsides < 3 || !BoundBrush (b[i]))
		{
			if (b[i]->numsides >= 3)
				Sys_FPrintf (SYS_VRB,"bogus brush after clip\n");
			FreeBrush (b[i]);
			b[i] = NULL;
		}
	}
	
	if ( !(b[0] && b[1]) )
	{
		if (!b[0] && !b[1])
			Sys_FPrintf (SYS_VRB,"split removed brush\n");
		else
			Sys_FPrintf (SYS_VRB,"split not on both sides\n");
		if (b[0])
		{
			FreeBrush (b[0]);
			*front = CopyBrush (brush);
		}
		if (b[1])
		{
			FreeBrush (b[1]);
			*back = CopyBrush (brush);
		}
		return;
	}
	
	// add the midwinding to both sides
	for (i=0 ; i<2 ; i++)
	{
		cs = &b[i]->sides[b[i]->numsides];
		b[i]->numsides++;

		cs->planenum = planenum^i^1;
		cs->shaderInfo = NULL;
		if (i==0)
			cs->winding = CopyWinding (midwinding);
		else
			cs->winding = midwinding;
	}
	
	{
		vec_t	v1;
		int		i;
		
		
		for (i=0 ; i<2 ; i++)
		{
			v1 = BrushVolume (b[i]);
			if (v1 < 1.0)
			{
				FreeBrush (b[i]);
				b[i] = NULL;
	//			Sys_FPrintf (SYS_VRB,"tiny volume after clip\n");
			}
		}
	}
	
	*front = b[0];
	*back = b[1];
}