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ericw-tools/common/polylib.c

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/* common/polylib.c */
#include <stddef.h>
#include <common/cmdlib.h>
#include <common/mathlib.h>
#include <common/polylib.h>
#define BOGUS_RANGE 8192
/*
* =============
* AllocWinding
* =============
*/
winding_t *
AllocWinding(int points)
{
winding_t *w;
int s;
s = sizeof(vec_t) * 3 * points + sizeof(int);
w = malloc(s);
memset(w, 0, s);
return w;
}
/*
* ============
* RemoveColinearPoints
* ============
*/
int c_removed;
void
RemoveColinearPoints(winding_t * w)
{
int i, j, k;
vec3_t v1, v2;
int nump;
vec3_t p[MAX_POINTS_ON_WINDING];
nump = 0;
for (i = 0; i < w->numpoints; i++) {
j = (i + 1) % w->numpoints;
k = (i + w->numpoints - 1) % w->numpoints;
VectorSubtract(w->p[j], w->p[i], v1);
VectorSubtract(w->p[i], w->p[k], v2);
VectorNormalize(v1);
VectorNormalize(v2);
if (DotProduct(v1, v2) < 0.999) {
VectorCopy(w->p[i], p[nump]);
nump++;
}
}
if (nump == w->numpoints)
return;
c_removed += w->numpoints - nump;
w->numpoints = nump;
memcpy(w->p, p, nump * sizeof(p[0]));
}
/*
* ============
* WindingPlane
* ============
*/
void
WindingPlane(winding_t * w, vec3_t normal, vec_t *dist)
{
vec3_t v1, v2;
VectorSubtract(w->p[1], w->p[0], v1);
VectorSubtract(w->p[2], w->p[0], v2);
CrossProduct(v1, v2, normal);
VectorNormalize(normal);
*dist = DotProduct(w->p[0], normal);
}
/*
* =============
* WindingArea
* =============
*/
vec_t
WindingArea(winding_t * w)
{
int i;
vec3_t d1, d2, cross;
vec_t total;
total = 0;
for (i = 2; i < w->numpoints; i++) {
VectorSubtract(w->p[i - 1], w->p[0], d1);
VectorSubtract(w->p[i], w->p[0], d2);
CrossProduct(d1, d2, cross);
total += 0.5 * VectorLength(cross);
}
return total;
}
/*
* =============
* WindingCenter
* =============
*/
void
WindingCenter(winding_t * w, vec3_t center)
{
int i;
vec3_t d1, d2, cross;
float scale;
VectorCopy(vec3_origin, center);
for (i = 0; i < w->numpoints; i++)
VectorAdd(w->p[i], center, center);
scale = 1.0 / w->numpoints;
VectorScale(center, scale, center);
}
/*
* =================
* BaseWindingForPlane
* =================
*/
winding_t *
BaseWindingForPlane(vec3_t normal, float dist)
{
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(normal[i]);
if (v > max) {
x = i;
max = v;
}
}
if (x == -1)
Error("%s: no axis found", __func__);
VectorCopy(vec3_origin, vup);
switch (x) {
case 0:
case 1:
vup[2] = 1;
break;
case 2:
vup[0] = 1;
break;
}
v = DotProduct(vup, normal);
VectorMA(vup, -v, normal, vup);
VectorNormalize(vup);
VectorScale(normal, dist, org);
CrossProduct(vup, normal, vright);
VectorScale(vup, 8192, vup);
VectorScale(vright, 8192, vright);
/* project a really big axis aligned box onto the plane */
w = AllocWinding(4);
VectorSubtract(org, vright, w->p[0]);
VectorAdd(w->p[0], vup, w->p[0]);
VectorAdd(org, vright, w->p[1]);
VectorAdd(w->p[1], vup, w->p[1]);
VectorAdd(org, vright, w->p[2]);
VectorSubtract(w->p[2], vup, w->p[2]);
VectorSubtract(org, vright, w->p[3]);
VectorSubtract(w->p[3], vup, w->p[3]);
w->numpoints = 4;
return w;
}
/*
* ==================
* CopyWinding
* ==================
*/
winding_t *
CopyWinding(winding_t * w)
{
int size;
winding_t *c;
size = offsetof(winding_t, p[w->numpoints]);
c = malloc(size);
memcpy(c, w, size);
return c;
}
/*
* =============
* ClipWinding
* =============
*/
void
ClipWinding(winding_t * in, vec3_t normal, vec_t dist,
winding_t ** front, winding_t ** back)
{
vec_t dists[MAX_POINTS_ON_WINDING + 4];
int sides[MAX_POINTS_ON_WINDING + 4];
int counts[3];
vec_t dot;
int i, j;
vec_t *p1, *p2;
vec3_t mid;
winding_t *f, *b;
int maxpts;
counts[0] = counts[1] = counts[2] = 0;
/* determine sides for each point */
for (i = 0; i < in->numpoints; i++) {
dot = DotProduct(in->p[i], normal);
dot -= 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];
*front = *back = NULL;
if (!counts[0]) {
*back = CopyWinding(in);
return;
}
if (!counts[1]) {
*front = CopyWinding(in);
return;
}
maxpts = in->numpoints + 4; /* can't use counts[0]+2 because */
/* of fp grouping errors */
*front = f = AllocWinding(maxpts);
*back = b = AllocWinding(maxpts);
for (i = 0; i < in->numpoints; i++) {
p1 = in->p[i];
if (sides[i] == SIDE_ON) {
VectorCopy(p1, f->p[f->numpoints]);
f->numpoints++;
VectorCopy(p1, b->p[b->numpoints]);
b->numpoints++;
continue;
}
if (sides[i] == SIDE_FRONT) {
VectorCopy(p1, f->p[f->numpoints]);
f->numpoints++;
}
if (sides[i] == SIDE_BACK) {
VectorCopy(p1, b->p[b->numpoints]);
b->numpoints++;
}
if (sides[i + 1] == SIDE_ON || sides[i + 1] == sides[i])
continue;
/* generate a split point */
p2 = in->p[(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 (normal[j] == 1)
mid[j] = dist;
else if (normal[j] == -1)
mid[j] = -dist;
else
mid[j] = p1[j] + dot * (p2[j] - p1[j]);
}
VectorCopy(mid, f->p[f->numpoints]);
f->numpoints++;
VectorCopy(mid, b->p[b->numpoints]);
b->numpoints++;
}
if (f->numpoints > maxpts || b->numpoints > maxpts)
Error("%s: points exceeded estimate", __func__);
if (f->numpoints > MAX_POINTS_ON_WINDING
|| b->numpoints > MAX_POINTS_ON_WINDING)
Error("%s: MAX_POINTS_ON_WINDING", __func__);
}
/*
* =================
* ChopWinding
* Returns the fragment of in that is on the front side
* of the cliping plane. The original is freed.
* =================
*/
winding_t *
ChopWinding(winding_t * in, vec3_t normal, vec_t dist)
{
winding_t *f, *b;
ClipWinding(in, normal, dist, &f, &b);
free(in);
if (b)
free(b);
return f;
}
/*
* =================
* CheckWinding
* =================
*/
void
CheckWinding(winding_t * w)
{
int i, j;
vec_t *p1, *p2;
vec_t d, edgedist;
vec3_t dir, edgenormal, facenormal;
vec_t area;
vec_t facedist;
if (w->numpoints < 3)
Error("%s: %i points", __func__, w->numpoints);
area = WindingArea(w);
if (area < 1)
Error("%s: %f area", __func__, area);
WindingPlane(w, facenormal, &facedist);
for (i = 0; i < w->numpoints; i++) {
p1 = w->p[i];
for (j = 0; j < 3; j++)
if (p1[j] > BOGUS_RANGE || p1[j] < -BOGUS_RANGE)
Error("%s: BUGUS_RANGE: %f", __func__, p1[j]);
j = i + 1 == w->numpoints ? 0 : i + 1;
/* check the point is on the face plane */
d = DotProduct(p1, facenormal) - facedist;
if (d < -ON_EPSILON || d > ON_EPSILON)
Error("%s: point off plane", __func__);
/* check the edge isn't degenerate */
p2 = w->p[j];
VectorSubtract(p2, p1, dir);
if (VectorLength(dir) < ON_EPSILON)
Error("%s: degenerate edge", __func__);
CrossProduct(facenormal, dir, edgenormal);
VectorNormalize(edgenormal);
edgedist = DotProduct(p1, edgenormal);
edgedist += ON_EPSILON;
/* all other points must be on front side */
for (j = 0; j < w->numpoints; j++) {
if (j == i)
continue;
d = DotProduct(w->p[j], edgenormal);
if (d > edgedist)
Error("%s: non-convex", __func__);
}
}
}
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