X-Git-Url: http://git.mutantstargoat.com/user/nuclear/?a=blobdiff_plain;f=src%2Fgeom.c;h=81e9df4117d181cd2263e0fc9aa42304077d8d13;hb=bf7eceb7d1cef825a64a1db7a20628f7d7005654;hp=21786644f8532b96a14701ef1ad0a76e931cae53;hpb=7e22a9e6549bf0ff36dc9a73c243de1f4b36b4a4;p=meshfrac

diff --git a/src/geom.c b/src/geom.c
index 2178664..81e9df4 100644
--- a/src/geom.c
+++ b/src/geom.c
@@ -1,3 +1,4 @@
+#include <stdio.h>
 #include "geom.h"
 #include "dynarr.h"
 
@@ -42,6 +43,41 @@ void poly_plane(const struct poly *poly, struct plane *plane)
 	poly_normal(poly, &plane->norm);
 }
 
+int plane_poly(const struct plane *plane, struct poly *poly, float size)
+{
+	static const float corn[][2] = {{1,1}, {-1,1}, {-1,-1}, {1, -1}};
+	int i;
+	cgm_vec3 up, right;
+	struct vertex *vptr;
+	size *= 0.5f;
+
+	if(!(poly->verts = dynarr_alloc(4, sizeof *poly->verts))) {
+		fprintf(stderr, "plane_poly: failed to allocate polygon vertices\n");
+		return -1;
+	}
+
+	cgm_vcons(&up, 0, 1, 0);
+	if(1.0f - fabs(cgm_vdot(&up, &plane->norm)) < 1e-2) {
+		cgm_vcons(&up, 0, 0, -1);
+	}
+	cgm_vcross(&right, &up, &plane->norm);
+	cgm_vnormalize(&right);
+	cgm_vcross(&up, &plane->norm, &right);
+	cgm_vnormalize(&up);
+
+	vptr = poly->verts;
+	for(i=0; i<4; i++) {
+		vptr->pos.x = plane->pt.x + (right.x * corn[i][0] + up.x * corn[i][1]) * size;
+		vptr->pos.y = plane->pt.y + (right.y * corn[i][0] + up.y * corn[i][1]) * size;
+		vptr->pos.z = plane->pt.z + (right.z * corn[i][0] + up.z * corn[i][1]) * size;
+
+		vptr->norm = plane->norm;
+		vptr->uv.x = vptr->uv.y = 0;
+		vptr++;
+	}
+	return 0;
+}
+
 float ray_plane(const cgm_ray *ray, const struct plane *plane)
 {
 	float ndotdir, t;
@@ -93,3 +129,85 @@ float ray_poly(const cgm_ray *ray, const struct poly *poly)
 	}
 	return t;
 }
+
+
+/* returns:
+ *  1 -> both inside
+ *  0 -> straddling and clipped
+ * -1 -> both outside
+ */
+static int clip_edge(struct poly *pout, const struct vertex *v0, const struct vertex *v1,
+		const struct plane *plane)
+{
+	float d0, d1, t;
+	cgm_ray ray;
+	struct vertex vnew;
+
+	d0 = plane_sdist(plane, &v0->pos);
+	d1 = plane_sdist(plane, &v1->pos);
+
+	ray.origin = v0->pos;
+	ray.dir = v1->pos;
+	cgm_vsub(&ray.dir, &v0->pos);
+
+	if(d0 >= 0.0) {
+		/* start inside */
+		if(d1 >= 0.0) {
+			/* all inside */
+			DYNARR_PUSH(pout->verts, v1);	/* append v1 */
+			return 1;
+		} else {
+			/* going out */
+			t = ray_plane(&ray, plane);
+			cgm_raypos(&vnew.pos, &ray, t);
+
+			cgm_vlerp(&vnew.norm, &v0->norm, &v1->norm, t);
+			vnew.uv.x = cgm_lerp(v0->uv.x, v1->uv.x, t);
+			vnew.uv.y = cgm_lerp(v0->uv.y, v1->uv.y, t);
+			/* append new vertex on the intersection point */
+			DYNARR_PUSH(pout->verts, &vnew);
+		}
+	} else {
+		/* start outside */
+		if(d1 >= 0) {
+			/* going in */
+			t = ray_plane(&ray, plane);
+			cgm_raypos(&vnew.pos, &ray, t);
+
+			cgm_vlerp(&vnew.norm, &v0->norm, &v1->norm, t);
+			vnew.uv.x = cgm_lerp(v0->uv.x, v1->uv.x, t);
+			vnew.uv.y = cgm_lerp(v0->uv.y, v1->uv.y, t);
+			/* append new vertex on the intersection point */
+			DYNARR_PUSH(pout->verts, &vnew);
+			/* then append v1 ... */
+			DYNARR_PUSH(pout->verts, v1);
+		} else {
+			/* all outside */
+			return -1;
+		}
+	}
+
+	return 0;
+}
+
+
+int clip_poly(struct poly *pout, const struct poly *pin, const struct plane *plane)
+{
+	int i, nextidx, res = 0, vnum;
+	int edges_clipped = 0;
+
+	dynarr_clear(pout->verts);
+
+	vnum = dynarr_size(pin->verts);
+	for(i=0; i<vnum; i++) {
+		nextidx = i + 1;
+		if(nextidx >= vnum) nextidx = 0;
+		res = clip_edge(pout, pin->verts + i, pin->verts + nextidx, plane);
+		if(res == 0) {
+			++edges_clipped;
+		}
+	}
+
+	return edges_clipped > 0 ? 0 : 1;
+
+}