nuclear@28: #include <stdio.h>
nuclear@28: #include <string.h>
nuclear@28: #include <assert.h>
nuclear@28: #include "mingl.h"
nuclear@28: #include "mglimpl.h"
nuclear@28: 
nuclear@28: static struct state *st;
nuclear@28: 
nuclear@28: static float distance_signed(vec3_t p, const struct plane *plane);
nuclear@28: static int intersect(const ray3_t *ray, const struct plane *plane, float *t);
nuclear@28: static int clip_polygon(struct vertex *vout, int *voutnum, const struct vertex *vin, int vnum,
nuclear@28: 		const struct plane *plane);
nuclear@28: 
nuclear@28: #define ZNEAR	MAX_CLIP_PLANES
nuclear@28: 
nuclear@28: int mgl_clip_init(struct state *state)
nuclear@28: {
nuclear@28: 	st = state;
nuclear@28: 
nuclear@28: 	memset(st->clip_planes, 0, sizeof st->clip_planes);
nuclear@28: 
nuclear@28: 	/* always setup a near clipping plane */
nuclear@28: 	st->clip_planes[ZNEAR].normal.x = st->clip_planes[ZNEAR].normal.y = 0;
nuclear@28: 	st->clip_planes[ZNEAR].normal.z = -1;
nuclear@28: 	st->clip_planes[ZNEAR].pt.x = st->clip_planes[ZNEAR].pt.y = 0;
nuclear@28: 	st->clip_planes[ZNEAR].pt.z = -0.5;
nuclear@28: 
nuclear@28: 	return 0;
nuclear@28: }
nuclear@28: 
nuclear@28: int mgl_clip_poly(struct vertex *v, int vnum)
nuclear@28: {
nuclear@28: 	int i, res, clipped_vnum;
nuclear@28: 	struct vertex tmp[6];
nuclear@28: 
nuclear@28: 	for(i=0; i<MAX_CLIP_PLANES + 1; i++) {
nuclear@28: 		if(i < ZNEAR && !mgl_isenabled(MGL_CLIP_PLANE0 + i)) {
nuclear@28: 			continue;
nuclear@28: 		}
nuclear@28: 
nuclear@28: 		res = clip_polygon(tmp, &clipped_vnum, v, vnum, st->clip_planes + i);
nuclear@28: 		if(res == -1) {
nuclear@28: 			/* the polygon was completely outside */
nuclear@28: 			return 0;
nuclear@28: 		}
nuclear@28: 		if(res == 0) {
nuclear@28: 			/* the polygon was clipped, update v and vnum */
nuclear@28: 			vnum = clipped_vnum;
nuclear@28: 			memcpy(v, tmp, clipped_vnum * sizeof *v);
nuclear@28: 		}
nuclear@28: 		/* otherwise the polygon was completely inside, nothing to do... */
nuclear@28: 	}
nuclear@28: 
nuclear@28: 	return vnum;
nuclear@28: }
nuclear@28: 
nuclear@28: static float distance_signed(vec3_t p, const struct plane *plane)
nuclear@28: {
nuclear@28: 	vec3_t ptdir;
nuclear@28: 	ptdir.x = p.x - plane->pt.x;
nuclear@28: 	ptdir.y = p.y - plane->pt.y;
nuclear@28: 	ptdir.z = p.z - plane->pt.z;
nuclear@28: 
nuclear@28: 	return vec3_dot(ptdir, plane->normal);
nuclear@28: }
nuclear@28: 
nuclear@28: static int intersect(const ray3_t *ray, const struct plane *plane, float *t)
nuclear@28: {
nuclear@28: 	vec3_t orig_pt_dir;
nuclear@28: 
nuclear@28: 	float ndotdir = vec3_dot(plane->normal, ray->dir);
nuclear@28: 	if(fabs(ndotdir) < 1e-4) {
nuclear@28: 		*t = 0.0f;
nuclear@28: 		return 0;
nuclear@28: 	}
nuclear@28: 
nuclear@28: 	orig_pt_dir.x = plane->pt.x - ray->origin.x;
nuclear@28: 	orig_pt_dir.y = plane->pt.y - ray->origin.y;
nuclear@28: 	orig_pt_dir.z = plane->pt.z - ray->origin.z;
nuclear@28: 
nuclear@28: 	*t = vec3_dot(plane->normal, orig_pt_dir) / ndotdir;
nuclear@28: 	return 1;
nuclear@28: }
nuclear@28: 
nuclear@28: static int clip_edge(struct vertex *poly, int *vnum, const struct vertex *v0,
nuclear@28: 		const struct vertex *v1, const struct plane *plane);
nuclear@28: 
nuclear@28: /* returns:
nuclear@28:  *  1 -> both inside
nuclear@28:  *  0 -> straddling and clipped
nuclear@28:  * -1 -> both outside
nuclear@28:  *
nuclear@28:  * the size of the vout polygon is returned throug voutnum
nuclear@28:  */
nuclear@28: static int clip_polygon(struct vertex *vout, int *voutnum, const struct vertex *vin, int vnum,
nuclear@28: 		const struct plane *plane)
nuclear@28: {
nuclear@28: 	int i;
nuclear@28: 	int edges_clipped = 0;
nuclear@28: 	int out_vnum = 0;
nuclear@28: 
nuclear@28: 	for(i=0; i<vnum; i++) {
nuclear@28: 		int res = clip_edge(vout, &out_vnum, vin + i, vin + (i + 1) % vnum, plane);
nuclear@28: 		if(res == 0) {
nuclear@28: 			edges_clipped++;
nuclear@28: 		}
nuclear@28: 	}
nuclear@28: 
nuclear@28: 	if(out_vnum <= 0) {
nuclear@28: 		assert(edges_clipped == 0);
nuclear@28: 		return -1;
nuclear@28: 	}
nuclear@28: 
nuclear@28: 	*voutnum = out_vnum;
nuclear@28: 	return edges_clipped > 0 ? 0 : 1;
nuclear@28: }
nuclear@28: 
nuclear@28: /* returns:
nuclear@28:  *  1 -> both inside
nuclear@28:  *  0 -> straddling and clipped
nuclear@28:  * -1 -> both outside
nuclear@28:  *
nuclear@28:  *  also returns the size of the polygon through vnumptr
nuclear@28:  */
nuclear@28: static int clip_edge(struct vertex *poly, int *vnumptr, const struct vertex *v0,
nuclear@28: 		const struct vertex *v1, const struct plane *plane)
nuclear@28: {
nuclear@28: 	vec3_t pos0, pos1;
nuclear@28: 	float d0, d1, t;
nuclear@28: 	ray3_t ray;
nuclear@28: 	int vnum = *vnumptr;
nuclear@28: 
nuclear@28: 	pos0.x = v0->pos.x; pos0.y = v0->pos.y; pos0.z = v0->pos.z;
nuclear@28: 	pos1.x = v1->pos.x; pos1.y = v1->pos.y; pos1.z = v1->pos.z;
nuclear@28: 
nuclear@28: 	d0 = distance_signed(pos0, plane);
nuclear@28: 	d1 = distance_signed(pos1, plane);
nuclear@28: 
nuclear@28: 	ray.origin = pos0;
nuclear@28: 	ray.dir.x = pos1.x - pos0.x;
nuclear@28: 	ray.dir.y = pos1.y - pos0.y;
nuclear@28: 	ray.dir.z = pos1.z - pos0.z;
nuclear@28: 
nuclear@28: 	if(d0 >= 0.0) {
nuclear@28: 		/* start inside */
nuclear@28: 		if(d1 >= 0.0) {
nuclear@28: 			/* all inside */
nuclear@28: 			poly[vnum++] = *v1;	/* append v1 */
nuclear@28: 			*vnumptr = vnum;
nuclear@28: 			return 1;
nuclear@28: 		} else {
nuclear@28: 			/* going out */
nuclear@28: 			intersect(&ray, plane, &t);
nuclear@28: 
nuclear@28: 			ray3_point(poly[vnum].pos, ray, t);
nuclear@28: 			poly[vnum].pos.w = 1.0;
nuclear@28: 
nuclear@28: 			vec3_lerp(poly[vnum].norm, v0->norm, v1->norm, t);
nuclear@28: 			vec2_lerp(poly[vnum].tc, v0->tc, v1->tc, t);
nuclear@28: 			poly[vnum].energy = v0->energy + (v1->energy - v0->energy) * t;
nuclear@28: 			poly[vnum].cidx = v0->cidx;
nuclear@28: 			vnum++;	/* append new vertex on the intersection point */
nuclear@28: 		}
nuclear@28: 	} else {
nuclear@28: 		/* start outside */
nuclear@28: 		if(d1 >= 0) {
nuclear@28: 			/* going in */
nuclear@28: 			intersect(&ray, plane, &t);
nuclear@28: 
nuclear@28: 			ray3_point(poly[vnum].pos, ray, t);
nuclear@28: 			poly[vnum].pos.w = 1.0;
nuclear@28: 
nuclear@28: 			vec3_lerp(poly[vnum].norm, v0->norm, v1->norm, t);
nuclear@28: 			vec2_lerp(poly[vnum].tc, v0->tc, v1->tc, t);
nuclear@28: 			poly[vnum].energy = v0->energy + (v1->energy - v0->energy) * t;
nuclear@28: 			poly[vnum].cidx = v0->cidx;
nuclear@28: 			vnum++;	/* append new vertex on the intersection point */
nuclear@28: 
nuclear@28: 			/* then append v1 ... */
nuclear@28: 			poly[vnum++] = *v1;
nuclear@28: 		} else {
nuclear@28: 			/* all outside */
nuclear@28: 			return -1;
nuclear@28: 		}
nuclear@28: 	}
nuclear@28: 
nuclear@28: 	*vnumptr = vnum;
nuclear@28: 	return 0;
nuclear@28: }