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