From: John Tsiombikas <nuclear@member.fsf.org>
Date: Sun, 29 Jan 2023 12:48:27 +0000 (+0200)
Subject: foo
X-Git-Url: http://git.mutantstargoat.com/user/nuclear/?p=meshfrac;a=commitdiff_plain;h=34e07fdc87e289e9ce574df7755e5e781136c20b

foo
---

diff --git a/src/frac.c b/src/frac.c
index 8a6bcae..071b5c2 100644
--- a/src/frac.c
+++ b/src/frac.c
@@ -4,6 +4,7 @@
 #include "dynarr.h"
 
 static void destroy_cell(struct frac_cell *cell);
+static int build_cell(struct fracture *frac, int cellidx);
 
 int frac_init(struct fracture *frac)
 {
@@ -70,6 +71,8 @@ int frac_num_cells(struct fracture *frac)
 	return dynarr_size(frac->cells);
 }
 
+/* --- step 1: generate a bunch of points (or let the user add them manually) */
+
 int frac_gen_points(struct fracture *frac, int num)
 {
 	int i;
@@ -97,11 +100,49 @@ int frac_gen_points(struct fracture *frac, int num)
 	return 0;
 }
 
+
+/* --- step 2: construct voronoi cells bounded by planes */
+
 int frac_build_cells(struct fracture *frac)
 {
+	int i;
+
+	for(i=0; i<dynarr_size(frac->cells); i++) {
+		if(build_cell(frac, i) == -1) {
+			return -1;
+		}
+	}
+
 	return -1;
 }
 
+static int build_cell(struct fracture *frac, int cellidx)
+{
+	int i, j, num;
+	struct plane plane, *pptr;
+	struct frac_cell *cell = frac->cells + cellidx;
+
+	num = dynarr_size(frac->cells);
+	for(i=0; i<num; i++) {
+		if(i == cellidx) continue;
+		midplane(&plane, &cell->pt, &frac->cells[i].pt);
+		if(!(pptr = dynarr_push(cell->planes, &plane))) {
+			return -1;
+		}
+		cell->planes = pptr;
+	}
+
+	/* clip all planes against each other to end up with a convex cell */
+	num = dynarr_size(cell->planes);
+	for(i=0; i<num; i++) {
+		for(j=0; j<num; j++) {
+			if(i == j) continue;
+
+			clip_poly...
+		}
+	}
+}
+
 int frac_build_shell(struct fracture *frac)
 {
 	return -1;
diff --git a/src/frac.h b/src/frac.h
index 03ae4e6..72192b7 100644
--- a/src/frac.h
+++ b/src/frac.h
@@ -3,11 +3,12 @@
 
 #include "cmesh.h"
 #include "cgmath/cgmath.h"
+#include "geom.h"
 
 struct frac_cell {
 	cgm_vec3 pt;
 	struct cmesh *mesh;
-	cgm_vec4 *planes;			/* dynarr */
+	struct plane *planes;			/* dynarr */
 };
 
 struct fracture {
diff --git a/src/geom.c b/src/geom.c
index 2178664..0b94385 100644
--- a/src/geom.c
+++ b/src/geom.c
@@ -42,6 +42,37 @@ 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 pos, up, right, dir;
+	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);
+
+	for(i=0; i<4; i++) {
+		v.x = plane->pt.x + (right.x * corn[i][0] + up.x * corn[i][1]) * size;
+		v.y = plane->pt.y + (right.y * corn[i][0] + up.y * corn[i][1]) * size;
+		v.z = plane->pt.z + (right.z * corn[i][0] + up.z * corn[i][1]) * size;
+
+
+
+
+}
+
 float ray_plane(const cgm_ray *ray, const struct plane *plane)
 {
 	float ndotdir, t;
@@ -93,3 +124,91 @@ 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;
+	int i, vnum = dynarr_size(pout->verts);
+	struct vertex vnew;
+
+	d0 = plane_sdist(plane, &v0->pos);
+	d1 = plane_sdist(plane, &v1->pos);
+
+	ray.orig = v0->pos;
+	ray.dir = v1->pos;
+	cgm_vsub(&ray.dir, &v0->pos);
+
+	for(i=0; i<3; i++) {
+		ray.origin[i] = pos0[i];
+		ray.dir[i] = pos1[i] - pos0[i];
+	}
+
+	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;
+
+}
diff --git a/src/geom.h b/src/geom.h
index 14faa82..ebb6659 100644
--- a/src/geom.h
+++ b/src/geom.h
@@ -21,9 +21,12 @@ float plane_sdist(const struct plane *p, const cgm_vec3 *pt);
 void midplane(struct plane *p, const cgm_vec3 *a, const cgm_vec3 *b);
 
 void poly_plane(const struct poly *poly, struct plane *plane);
+int plane_poly(const struct plane *plane, struct poly *poly, float size);
 
 /* returns negative if there's no intersection, parametric distance if there is */
 float ray_plane(const cgm_ray *ray, const struct plane *plane);
 float ray_poly(const cgm_ray *ray, const struct poly *poly);
 
+int clip_poly(struct poly *pout, const struct poly *pin, const struct plane *plane);
+
 #endif	/* GEOM_H_ */