quakeforge/tools/qfbsp/source/winding.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.
*/
#ifdef HAVE_CONFIG_H
# include "config.h"
#endif

static __attribute__ ((used)) const char rcsid[] =
	"$Id$";

#ifdef HAVE_STRING_H
# include <string.h>
#endif
#ifdef HAVE_STRINGS_H
# include <strings.h>
#endif
#ifdef HAVE_MALLOC_H
#include <malloc.h>
#endif
#include <stdlib.h>

#include "QF/sys.h"

#include "bsp5.h"
#include "winding.h"

int         c_activewindings, c_peakwindings;

winding_t *
BaseWindingForPlane (plane_t *p)
{
	int         i, x;
	vec_t       max, v;
	vec3_t      org, vright, vup;
	winding_t  *w;

	// find the major axis

	max = -BOGUS_RANGE;
	x = -1;
	for (i = 0; i < 3; i++) {
		v = fabs (p->normal[i]);
		if (v > max) {
			x = i;
			max = v;
		}
	}
	if (x == -1)
		Sys_Error ("BaseWindingForPlane: no axis found");

	VectorZero (vup);
	switch (x) {
		case 0:
		case 1:
			vup[2] = 1;
			break;
		case 2:
			vup[0] = 1;
			break;
	}

	v = DotProduct (vup, p->normal);
	VectorMultSub (vup, v, p->normal, vup);
	_VectorNormalize (vup);

	VectorScale (p->normal, p->dist, org);

	CrossProduct (vup, p->normal, vright);

	VectorScale (vup, BOGUS_RANGE, vup);
	VectorScale (vright, BOGUS_RANGE, vright);

	// project a really big axis aligned box onto the plane
	w = NewWinding (4);

	VectorSubtract (org, vright, w->points[0]);
	VectorAdd (w->points[0], vup, w->points[0]);

	VectorAdd (org, vright, w->points[1]);
	VectorAdd (w->points[1], vup, w->points[1]);

	VectorAdd (org, vright, w->points[2]);
	VectorSubtract (w->points[2], vup, w->points[2]);

	VectorSubtract (org, vright, w->points[3]);
	VectorSubtract (w->points[3], vup, w->points[3]);

	w->numpoints = 4;

	return w;
}

winding_t *
CopyWinding (winding_t *w)
{
	size_t      size;
	winding_t  *c;

	size = (size_t) (uintptr_t) &((winding_t *) 0)->points[w->numpoints];
	c = malloc (size);
	memcpy (c, w, size);
	return c;
}

winding_t *
CopyWindingReverse (winding_t *w)
{
	int         i;
	size_t      size;
	winding_t  *c;

	size = (size_t) (uintptr_t) &((winding_t *) 0)->points[w->numpoints];
	c = malloc (size);
	c->numpoints = w->numpoints;
	for (i = 0; i < w->numpoints; i++) {
		// add points backwards
		VectorCopy (w->points[w->numpoints - 1 - i], c->points[i]);
	}
	return c;
}

/*
	ClipWinding

	Clips the winding to the plane, returning the new winding on the positive
	side.

	Frees the input winding.

	If keepon is true, an exactly on-plane winding will be saved, otherwise
	it will be clipped away.
*/
winding_t *
ClipWinding (winding_t *in, plane_t *split, qboolean keepon)
{
	int         maxpts, i, j;
	int        *sides;
	int         counts[3];
	vec_t       dot;
	vec_t      *dists;
	vec_t      *p1, *p2;
	vec3_t      mid;
	winding_t  *neww;

	counts[0] = counts[1] = counts[2] = 0;

	sides = alloca ((in->numpoints + 1) * sizeof (int));
	dists = alloca ((in->numpoints + 1) * sizeof (vec_t));

	// determine sides for each point
	for (i = 0; i < in->numpoints; i++) {
		dot = DotProduct (in->points[i], split->normal);
		dot -= split->dist;
		dists[i] = dot;
		if (dot > ON_EPSILON)
			sides[i] = SIDE_FRONT;
		else if (dot < -ON_EPSILON)
			sides[i] = SIDE_BACK;
		else {
			sides[i] = SIDE_ON;
		}
		counts[sides[i]]++;
	}
	sides[i] = sides[0];
	dists[i] = dists[0];

	if (keepon && !counts[SIDE_FRONT] && !counts[SIDE_BACK])
		return in;

	if (!counts[SIDE_FRONT]) {
		FreeWinding (in);
		return NULL;
	}
	if (!counts[SIDE_BACK])
		return in;
	for (maxpts = 0, i = 0; i < in->numpoints; i++) {
		if (!(sides[i] & 1))
			maxpts++;
		if ((sides[i] ^ 1) == sides[i + 1])
			maxpts++;
	}
	neww = NewWinding (maxpts);

	for (i = 0; i < in->numpoints; i++) {
		p1 = in->points[i];

		if (sides[i] == SIDE_ON) {
			if (neww->numpoints == maxpts)
				Sys_Error ("ClipWinding: points exceeded estimate");
			VectorCopy (p1, neww->points[neww->numpoints]);
			neww->numpoints++;
			continue;
		}

		if (sides[i] == SIDE_FRONT) {
			if (neww->numpoints == maxpts)
				Sys_Error ("ClipWinding: points exceeded estimate");
			VectorCopy (p1, neww->points[neww->numpoints]);
			neww->numpoints++;
		}

		if (sides[i + 1] == SIDE_ON || sides[i + 1] == sides[i])
			continue;

		if (neww->numpoints == maxpts)
			Sys_Error ("ClipWinding: points exceeded estimate");

		// generate a split point
		p2 = in->points[(i + 1) % in->numpoints];

		dot = dists[i] / (dists[i] - dists[i + 1]);
		for (j = 0; j < 3; j++) {		// avoid round off error when possible
			if (split->normal[j] == 1)
				mid[j] = split->dist;
			else if (split->normal[j] == -1)
				mid[j] = -split->dist;
			else
				mid[j] = p1[j] + dot * (p2[j] - p1[j]);
		}

		VectorCopy (mid, neww->points[neww->numpoints]);
		neww->numpoints++;
	}

	// free the original winding
	FreeWinding (in);

	return neww;
}

/*
	DivideWinding

	Divides a winding by a plane, producing one or two windings.  The
	original winding is not damaged or freed.  If on only one side, the
	returned winding will be the input winding.  If on both sides, two
	new windings will be created.
*/
void
DivideWinding (winding_t *in, plane_t *split, winding_t **front,
			   winding_t **back)
{
	int         i;
	int         counts[3];
	plane_t     plane;
	vec_t       dot;
	winding_t  *tmp;

	counts[0] = counts[1] = counts[2] = 0;

	// determine sides for each point
	for (i = 0; i < in->numpoints; i++) {
		dot = DotProduct (in->points[i], split->normal) - split->dist;
		if (dot > ON_EPSILON)
			counts[SIDE_FRONT]++;
		else if (dot < -ON_EPSILON)
			counts[SIDE_BACK]++;
	}

	*front = *back = NULL;

	if (!counts[SIDE_FRONT]) {
		*back = in;
		return;
	}
	if (!counts[SIDE_BACK]) {
		*front = in;
		return;
	}

	tmp = CopyWinding (in);
	*front = ClipWinding (tmp, split, 0);

	plane.dist = -split->dist;
	VectorNegate (split->normal, plane.normal);

	tmp = CopyWinding (in);
	*back = ClipWinding (tmp, &plane, 0);
}

winding_t *
NewWinding (int points)
{
	size_t      size;
	winding_t  *w;

	if (points < 3)
		Sys_Error ("NewWinding: %i points", points);

	c_activewindings++;
	if (c_activewindings > c_peakwindings)
		c_peakwindings = c_activewindings;

	size = (size_t) (uintptr_t) &((winding_t *) 0)->points[points];
	w = malloc (size);
	memset (w, 0, size);

	return w;
}

void
FreeWinding (winding_t *w)
{
	c_activewindings--;
	free (w);
}