make backface and coplanar optional
This commit is contained in:
Trammell hudson
parent
f2fe56eb86
commit
5d9e0b3673
2
camera.c
2
camera.c
@ -90,7 +90,7 @@ camera_project(
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// is this rotating?
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float px = p.p[1] / p.p[2];
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float py = p.p[0] / p.p[2];
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float pz = p.p[2];
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float pz = p.p[2] / c->zoom;
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// return it to the caller
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v_out->p[0] = px * c->zoom;
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121
hiddenwire.c
121
hiddenwire.c
@ -835,6 +835,7 @@ if(0) fprintf(stderr, "%p: %f,%f inside %f,%f %f,%f %f,%f\n",
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}
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tri_t *
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tri_new(
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const v3_t * p
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@ -844,14 +845,13 @@ tri_new(
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if (!t)
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return NULL;
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for(int i = 0 ; i < 3 ; i++)
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for(int j = 0 ; j < 3 ; j++)
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t->p[i].p[j] = p[i].p[j];
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t->p[i] = p[i];
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// precompute the normal
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t->normal = v3_cross(
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t->normal = v3_norm(v3_cross(
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v3_sub(t->p[1], t->p[0]),
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v3_sub(t->p[2], t->p[1])
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);
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));
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// compute the bounding box for the triangle
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@ -963,6 +963,52 @@ tri_print(
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);
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}
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/* Check if two triangles are coplanar and share an edge.
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*
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* Returns -1 if not coplanar, 0-2 for the edge in t0 that they share.
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*/
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int
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tri_coplanar(
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const tri_t * const t0,
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const tri_t * const t1,
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const float coplanar_eps
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)
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{
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// the two normals must be parallel-enough
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const float angle = v3_mag(v3_sub(t0->normal, t1->normal));
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if (angle < -coplanar_eps || +coplanar_eps < angle)
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return -1;
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// find if there are two points shared
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unsigned matches = 0;
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for(int i = 0 ; i < 3 ; i++)
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{
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for(int j = 0 ; j < 3 ; j++)
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{
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if (!v3_eq(&t0->p[i], &t1->p[j]))
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continue;
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matches |= 1 << i;
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break;
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}
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}
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switch(matches)
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{
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case 0x3: return 0;
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case 0x6: return 1;
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case 0x5: return 2;
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case 0x7:
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fprintf(stderr, "uh, three points match?\n");
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tri_print(t0);
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tri_print(t1);
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return -1;
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default:
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// no shared edge
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return -1;
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}
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}
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/** Find the Z point of a given xy point along the segment from p0 to p1.
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*
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* Returns -1 if there is no known Z point.
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@ -1337,6 +1383,11 @@ int main(
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const stl_face_t * const stl_faces = (const void*)(hdr+1);
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const int num_triangles = hdr->num_triangles;
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int backface = 1;
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int coplanar = 1;
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int hidden = 1;
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float coplanar_eps = 0.01;
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if(debug)
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{
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fprintf(stderr, "header: '%s'\n", hdr->header);
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@ -1351,7 +1402,7 @@ int main(
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printf("<svg xmlns=\"http://www.w3.org/2000/svg\">\n");
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float off_x = 500;
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float off_y = 1200;
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float off_y = 500;
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printf("<g transform=\"translate(%f %f)\">\n", off_x, off_y);
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int rejected = 0;
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@ -1372,6 +1423,14 @@ int main(
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for(int j = 0 ; j < 3 ; j++)
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camera_project(cam, &stl->p[j], &s[j]);
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fprintf(stderr, "%.3f,%.3f,%.3f -> %.0f,%.0f\n",
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stl->p[0].p[0],
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stl->p[0].p[1],
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stl->p[0].p[2],
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s[0].p[0],
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s[0].p[1]
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);
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tri_t * const tri = tri_new(s);
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// reject this face if any of the vertices are behind us
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@ -1381,7 +1440,7 @@ int main(
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// do a back-face cull to determine if this triangle
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// is not facing us. we have to determine the orientation
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// from the winding of the new projection
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if (tri->normal.p[2] <= 0)
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if (backface && tri->normal.p[2] <= 0)
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goto reject;
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retained++;
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@ -1389,15 +1448,6 @@ int main(
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// it passes the first tests, so insert the triangle
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// into the list and the three line segments
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tri_insert(&zlist, tri);
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for(int j = 0 ; j < 3 ; j++)
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{
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seg_t * s = seg_new(tri->p[j], tri->p[(j+1) % 3]);
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s->next = slist;
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slist = s;
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}
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continue;
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reject:
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@ -1408,10 +1458,48 @@ reject:
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if (debug)
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fprintf(stderr, "Retained %d, rejected %d triangles\n", retained, rejected);
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// generate a list of segments, dropping any coplanar ones
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rejected = 0;
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for(tri_t * t = zlist ; t ; t = t->next)
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{
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unsigned matches = 0;
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if(coplanar)
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for(tri_t * t2 = zlist ; t2 ; t2 = t2->next)
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{
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if (t == t2)
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continue;
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const int edge = tri_coplanar(t, t2, coplanar_eps);
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if (edge < 0)
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continue;
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matches |= 1 << edge;
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}
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for(int j = 0 ; j < 3 ; j++)
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{
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// drop any that are coplanar
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if (matches & (1 << j))
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{
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rejected++;
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continue;
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}
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seg_t * s = seg_new(t->p[j], t->p[(j+1) % 3]);
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s->next = slist;
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slist = s;
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}
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}
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if (debug)
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fprintf(stderr, "Rejected %d coplanar segments\n", rejected);
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// we now have a z-sorted list of triangles
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rejected = 0;
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if(1)
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if(hidden)
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{
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// work on each segment, intersecting it with all of the triangles
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while(slist)
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@ -1420,7 +1508,6 @@ reject:
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slist = s->next;
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tri_seg_intersect(zlist, s, &slist_visible);
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}
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} else {
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// don't do any intersection tests
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