quakeforge/tools/qfbsp/source/merge.c

/*  Copyright (C) 1996-1997  Id Software, Inc.

    This program 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.

    This program 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 this program; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA

    See file, 'COPYING', for details.
*/

// merge.c

#ifdef HAVE_CONFIG_H
# include "config.h"
#endif

#include "QF/sys.h"

#include "bsp5.h"


#define CONTINUOUS_EPSILON	0.001

/*
================
CheckColinear

================
*/
void
CheckColinear (face_t * f)
{
	int         i, j;
	vec3_t      v1, v2;

	for (i = 0; i < f->numpoints; i++) {
// skip the point if the vector from the previous point is the same
// as the vector to the next point
		j = (i - 1 < 0) ? f->numpoints - 1 : i - 1;
		VectorSubtract (f->pts[i], f->pts[j], v1);
		VectorNormalize (v1);

		j = (i + 1 == f->numpoints) ? 0 : i + 1;
		VectorSubtract (f->pts[j], f->pts[i], v2);
		VectorNormalize (v2);

		if (VectorCompare (v1, v2))
			Sys_Error ("Colinear edge");
	}

}


/*
=============
TryMerge

If two polygons share a common edge and the edges that meet at the
common points are both inside the other polygons, merge them

Returns NULL if the faces couldn't be merged, or the new face.
The originals will NOT be freed.
=============
*/
face_t     *
TryMerge (face_t * f1, face_t * f2)
{
	vec_t      *p1, *p2, *p3, *p4, *back;
	face_t     *newf;
	int         i, j, k, l;
	vec3_t      normal, delta, planenormal;
	vec_t       dot;
	plane_t    *plane;
	qboolean    keep1, keep2;

	if (f1->numpoints == -1 || f2->numpoints == -1)
		return NULL;
	if (f1->planeside != f2->planeside)
		return NULL;
	if (f1->texturenum != f2->texturenum)
		return NULL;
	if (f1->contents[0] != f2->contents[0])
		return NULL;
	if (f1->contents[1] != f2->contents[1])
		return NULL;

//
// find a common edge
//  
	p1 = p2 = NULL;						// stop compiler warning
	j = 0;								// 

	for (i = 0; i < f1->numpoints; i++) {
		p1 = f1->pts[i];
		p2 = f1->pts[(i + 1) % f1->numpoints];
		for (j = 0; j < f2->numpoints; j++) {
			p3 = f2->pts[j];
			p4 = f2->pts[(j + 1) % f2->numpoints];
			for (k = 0; k < 3; k++) {
				if (fabs (p1[k] - p4[k]) > EQUAL_EPSILON)
					break;
				if (fabs (p2[k] - p3[k]) > EQUAL_EPSILON)
					break;
			}
			if (k == 3)
				break;
		}
		if (j < f2->numpoints)
			break;
	}

	if (i == f1->numpoints)
		return NULL;					// no matching edges

//
// check slope of connected lines
// if the slopes are colinear, the point can be removed
//
	plane = &planes[f1->planenum];
	VectorCopy (plane->normal, planenormal);
	if (f1->planeside)
		VectorSubtract (vec3_origin, planenormal, planenormal);

	back = f1->pts[(i + f1->numpoints - 1) % f1->numpoints];
	VectorSubtract (p1, back, delta);
	CrossProduct (planenormal, delta, normal);
	VectorNormalize (normal);

	back = f2->pts[(j + 2) % f2->numpoints];
	VectorSubtract (back, p1, delta);
	dot = DotProduct (delta, normal);
	if (dot > CONTINUOUS_EPSILON)
		return NULL;					// not a convex polygon
	keep1 = dot < -CONTINUOUS_EPSILON;

	back = f1->pts[(i + 2) % f1->numpoints];
	VectorSubtract (back, p2, delta);
	CrossProduct (planenormal, delta, normal);
	VectorNormalize (normal);

	back = f2->pts[(j + f2->numpoints - 1) % f2->numpoints];
	VectorSubtract (back, p2, delta);
	dot = DotProduct (delta, normal);
	if (dot > CONTINUOUS_EPSILON)
		return NULL;					// not a convex polygon
	keep2 = dot < -CONTINUOUS_EPSILON;

//
// build the new polygon
//
	if (f1->numpoints + f2->numpoints > MAXEDGES) {
//      Sys_Error ("TryMerge: too many edges!");
		return NULL;
	}

	newf = NewFaceFromFace (f1);

// copy first polygon
	for (k = (i + 1) % f1->numpoints; k != i; k = (k + 1) % f1->numpoints) {
		if (k == (i + 1) % f1->numpoints && !keep2)
			continue;

		VectorCopy (f1->pts[k], newf->pts[newf->numpoints]);
		newf->numpoints++;
	}

// copy second polygon
	for (l = (j + 1) % f2->numpoints; l != j; l = (l + 1) % f2->numpoints) {
		if (l == (j + 1) % f2->numpoints && !keep1)
			continue;
		VectorCopy (f2->pts[l], newf->pts[newf->numpoints]);
		newf->numpoints++;
	}

	return newf;
}


/*
===============
MergeFaceToList
===============
*/
qboolean    mergedebug;
face_t     *
MergeFaceToList (face_t * face, face_t * list)
{
	face_t     *newf, *f;

	for (f = list; f; f = f->next) {
//CheckColinear (f);        
		if (mergedebug) {
			Draw_ClearWindow ();
			Draw_DrawFace (face);
			Draw_DrawFace (f);
			Draw_SetBlack ();
		}
		newf = TryMerge (face, f);
		if (!newf)
			continue;
		FreeFace (face);
		f->numpoints = -1;				// merged out
		return MergeFaceToList (newf, list);
	}

// didn't merge, so add at start
	face->next = list;
	return face;
}


/*
===============
FreeMergeListScraps
===============
*/
face_t     *
FreeMergeListScraps (face_t * merged)
{
	face_t     *head, *next;

	head = NULL;
	for (; merged; merged = next) {
		next = merged->next;
		if (merged->numpoints == -1)
			FreeFace (merged);
		else {
			merged->next = head;
			head = merged;
		}
	}

	return head;
}


/*
===============
MergePlaneFaces
===============
*/
void
MergePlaneFaces (surface_t * plane)
{
	face_t     *f1, *next;
	face_t     *merged;

	merged = NULL;

	for (f1 = plane->faces; f1; f1 = next) {
		next = f1->next;
		merged = MergeFaceToList (f1, merged);
	}

// chain all of the non-empty faces to the plane
	plane->faces = FreeMergeListScraps (merged);
}


/*
============
MergeAll
============
*/
void
MergeAll (surface_t * surfhead)
{
	surface_t  *surf;
	int         mergefaces;
	face_t     *f;

	printf ("---- MergeAll ----\n");

	mergefaces = 0;
	for (surf = surfhead; surf; surf = surf->next) {
		MergePlaneFaces (surf);
		Draw_ClearWindow ();
		for (f = surf->faces; f; f = f->next) {
			Draw_DrawFace (f);
			mergefaces++;
		}
	}

	printf ("%i mergefaces\n", mergefaces);
}