split tri.h into tri.c for test purposes
This commit is contained in:
Trammell hudson
parent
ea48ff38dc
commit
a356ac6490
5
Makefile
5
Makefile
@ -16,7 +16,10 @@ unfold: unfold.o
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wireframe: wireframe.o
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corners: corners.o stl_3d.o
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faces: faces.o stl_3d.o
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hiddenwire: hiddenwire.o camera.o
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hiddenwire: hiddenwire.o camera.o tri.o
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# Test the triangle intersection code
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test-intersect: test-intersect.o tri.o
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clean:
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$(RM) *.o
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4
seg.h
4
seg.h
@ -10,7 +10,7 @@ struct _seg_t {
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seg_t * next;
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};
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seg_t *
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static inline seg_t *
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seg_new(
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const v3_t p0,
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const v3_t p1
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@ -29,7 +29,7 @@ seg_new(
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}
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void
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static inline void
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seg_print(
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const seg_t * const s
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)
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614
tri.c
Normal file
614
tri.c
Normal file
@ -0,0 +1,614 @@
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/*
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* Triangle manipulations
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*/
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#include <stdio.h>
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#include <math.h>
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#include <stdint.h>
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#include "tri.h"
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int tri_debug = 0;
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tri_t *
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tri_new(
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const v3_t * p_cam,
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const v3_t * p_xyz
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)
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{
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tri_t * const t = calloc(1, sizeof(*t));
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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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t->p[i] = p_cam[i];
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// precompute the normals
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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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t->normal_xyz = v3_norm(v3_cross(
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v3_sub(p_xyz[1], p_xyz[0]),
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v3_sub(p_xyz[2], p_xyz[1])
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));
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// compute the bounding box for the triangle in camera space
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for(int j = 0 ; j < 3 ; j++)
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{
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t->min[j] = min(min(t->p[0].p[j], t->p[1].p[j]), t->p[2].p[j]);
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t->max[j] = max(max(t->p[0].p[j], t->p[1].p[j]), t->p[2].p[j]);
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}
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return t;
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}
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// insert a triangle into our z-sorted list
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void
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tri_insert(
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tri_t ** zlist,
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tri_t * t
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)
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{
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while(1)
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{
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tri_t * const iter = *zlist;
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if (!iter)
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break;
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// check to see if our new triangle is closer than
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// the current triangle
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if(iter->min[2] > t->min[2])
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break;
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zlist = &(iter->next);
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}
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// either we reached the end of the list,
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// or we have found where our new triangle is sorted
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t->next = *zlist;
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t->prev = zlist;
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*zlist = t;
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if (t->next)
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t->next->prev = &t->next;
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}
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void
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tri_delete(tri_t * t)
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{
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if (t->next)
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t->next->prev = t->prev;
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if (t->prev)
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*(t->prev) = t->next;
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t->next = NULL;
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t->prev = NULL;
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free(t);
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}
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// Compute the 2D area of a triangle in screen space
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// using Heron's formula
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float
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tri_area_2d(
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const tri_t * const t
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)
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{
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const float a = v3_dist_2d(&t->p[0], &t->p[1]);
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const float b = v3_dist_2d(&t->p[1], &t->p[2]);
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const float c = v3_dist_2d(&t->p[2], &t->p[0]);
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const float s = (a + b + c) / 2;
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return sqrt(s * (s-a) * (s-b) * (s-c));
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}
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void
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tri_print(
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const tri_t * const t
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)
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{
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fprintf(stderr, "%.0f,%.0f,%.0f %.0f,%.0f,%.0f %.0f,%.0f,%.0f norm %.3f,%.3f,%.3f\n",
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t->p[0].p[0],
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t->p[0].p[1],
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t->p[0].p[2],
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t->p[1].p[0],
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t->p[1].p[1],
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t->p[1].p[2],
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t->p[2].p[0],
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t->p[2].p[1],
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t->p[2].p[2],
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t->normal.p[0],
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t->normal.p[1],
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t->normal.p[2]
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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_xyz, t1->normal_xyz));
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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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/*
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* Find the Z point of an XY coordinate in a triangle.
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*
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* p can be written as a combination of t01 and t02,
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* p - t0 = a * (t1 - t0) + b * (t2 - t0)
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* setting t0 to 0, this becomes:
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* p = a * t1 + b * t2
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* which is two equations with two unknowns
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*
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* Returns true if the point is inside the triangle
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*/
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int
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tri_find_z(
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const tri_t * const t,
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const v3_t * const p,
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float * const zout
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)
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{
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const float t1x = t->p[1].p[0] - t->p[0].p[0];
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const float t1y = t->p[1].p[1] - t->p[0].p[1];
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const float t1z = t->p[1].p[2] - t->p[0].p[2];
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const float t2x = t->p[2].p[0] - t->p[0].p[0];
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const float t2y = t->p[2].p[1] - t->p[0].p[1];
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const float t2z = t->p[2].p[2] - t->p[0].p[2];
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const float px = p->p[0] - t->p[0].p[0];
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const float py = p->p[1] - t->p[0].p[1];
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const float a = (px * t2y - py * t2x) / (t1x * t2y - t2x * t1y);
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const float b = (px * t1y - py * t1x) / (t2x * t1y - t1x * t2y);
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const float z = t->p[0].p[2] + a * t1z + b * t2z;
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if (zout)
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*zout = z;
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return 0 <= a && 0 <= b && a + b <= 1;
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}
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/** Compute the points of intersection for two segments in 2d, and z points.
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*
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* This is a specialized ray intersection algorithm for the
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* hidden wire-frame removal code that computes the intersection
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* points for two rays (in 2D, "orthographic") and then computes
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* the Z depth for the intersections along each of the segments.
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*
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* Returns -1 for non-intersecting, otherwise a ratio of how far
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* along the intersection is on the l0.
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*/
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float
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hidden_intersect(
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const v3_t * const p0,
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const v3_t * const p1,
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const v3_t * const p2,
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const v3_t * const p3,
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v3_t * const l0_int,
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v3_t * const l1_int
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)
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{
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const float p0_x = p0->p[0];
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const float p0_y = p0->p[1];
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const float p0_z = p0->p[2];
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const float p1_x = p1->p[0];
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const float p1_y = p1->p[1];
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const float p1_z = p1->p[2];
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const float p2_x = p2->p[0];
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const float p2_y = p2->p[1];
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const float p2_z = p2->p[2];
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const float p3_x = p3->p[0];
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const float p3_y = p3->p[1];
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const float p3_z = p3->p[2];
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const float s1_x = p1_x - p0_x;
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const float s1_y = p1_y - p0_y;
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const float s2_x = p3_x - p2_x;
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const float s2_y = p3_y - p2_y;
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// compute r x s
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const float d = -s2_x * s1_y + s1_x * s2_y;
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// if they are close to parallel, then we do not need to check
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// for intersection (we define that as "non-intersecting")
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if (-EPS < d && d < EPS)
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return -1;
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// Compute how far along each line they would interesect
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const float r0 = ( s2_x * (p0_y - p2_y) - s2_y * (p0_x - p2_x)) / d;
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const float r1 = (-s1_y * (p0_x - p2_x) + s1_x * (p0_y - p2_y)) / d;
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// if they are not within the ratio (0,1), then the intersecton occurs
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// outside of the segments and is not of concern
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if (r0 < 0 || r0 > 1)
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return -1;
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if (r1 < 0 || r1 > 1)
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return -1;
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// Collision detected with the segments
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if(0) fprintf(stderr, "collision: %.0f,%.0f,%.0f->%.0f,%.0f,%.0f %.0f,%.0f,%.0f->%.0f,%.0f,%.0f == %.3f,%.3f\n",
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p0_x, p0_y, p0_z,
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p1_x, p1_y, p1_z,
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p2_x, p2_y, p2_z,
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p3_x, p3_y, p2_z,
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r0,
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r1
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);
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const float ix = p0_x + (r0 * s1_x);
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const float iy = p0_y + (r0 * s1_y);
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// compute the z intercept for each on the two different coordinates
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if(l0_int)
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{
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*l0_int = (v3_t){{
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ix,
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iy,
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p0_z + r0 * (p1_z - p0_z)
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}};
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}
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if(l1_int)
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{
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*l1_int = (v3_t){{
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ix,
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iy,
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p2_z + r1 * (p3_z - p2_z)
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}};
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}
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return r0;
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}
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/*
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* Recursive algorithm:
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* Given a line segment and a list of triangles,
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* find if the line segment crosses any triangle.
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* If it crosses a triangle the segment will be shortened
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* and an additional one might be created.
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* Recusively try intersecting the new segment (starting at the same triangle)
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* and then continue trying the shortened segment.
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*/
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void
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tri_seg_intersect(
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const tri_t * zlist,
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seg_t * s,
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seg_t ** slist_visible
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)
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{
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const float p0z = s->p[0].p[2];
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const float p1z = s->p[1].p[2];
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const float seg_max_z = max(p0z, p1z);
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// avoid processing empty segments
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const float seg_len = v3_len(&s->p[0], &s->p[1]);
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if (seg_len < EPS)
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return;
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static int recursive;
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recursive++;
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//fprintf(stderr, "%d: processing segment ", recursive); seg_print(s);
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fprintf(stderr, "--- recursive %d\n", recursive);
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seg_print(s);
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for( const tri_t * t = zlist ; t ; t = t->next )
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{
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// if the segment is closer than the triangle,
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// then we no longer have to check any further into
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// the zlist (it is sorted by depth).
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if (seg_max_z <= t->min[2])
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break;
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#if 0
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// make sure that we're not comparing to our own triangle
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// or one that shares an edge with us (which might be in
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// a different order)
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if (v2_eq(s->src[0].p, t->p[0].p, 0.0005)
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&& v2_eq(s->src[1].p, t->p[1].p, 0.0005))
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continue;
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if (v2_eq(s->src[0].p, t->p[1].p, 0.0005)
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&& v2_eq(s->src[1].p, t->p[2].p, 0.0005))
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continue;
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if (v2_eq(s->src[0].p, t->p[2].p, 0.0005)
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&& v2_eq(s->src[1].p, t->p[0].p, 0.0005))
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continue;
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if (v2_eq(s->src[0].p, t->p[1].p, 0.0005)
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&& v2_eq(s->src[1].p, t->p[0].p, 0.0005))
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continue;
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if (v2_eq(s->src[0].p, t->p[2].p, 0.0005)
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&& v2_eq(s->src[1].p, t->p[1].p, 0.0005))
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continue;
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if (v2_eq(s->src[0].p, t->p[0].p, 0.0005)
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&& v2_eq(s->src[1].p, t->p[2].p, 0.0005))
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continue;
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#endif
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if (tri_debug >= 2)
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tri_print(t);
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/*
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// if the segment is co-linear to any of the
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// triangle edges, include it
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for(int i = 0 ; i < 3 ; i++)
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{
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if (parallel(
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&s->p[0], &s->p[1],
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&t->p[i], &t->p[(i+1)%3]
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))
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goto next_segment;
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}
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*/
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float z0, z1;
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int inside0 = tri_find_z(t, &s->p[0], &z0);
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int inside1 = tri_find_z(t, &s->p[1], &z1);
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if (tri_debug >= 2 && (inside0 || inside1))
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{
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fprintf(stderr, "inside %d %d\n", inside0, inside1);
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}
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// if both are inside but the segment is infront of the
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// triangle, then we retain the segment.
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// otherwies we discard the segment
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if (inside0 && inside1)
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{
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if (s->p[0].p[2] <= z0
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&& s->p[1].p[2] <= z1)
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continue;
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if (tri_debug >= 2)
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fprintf(stderr, "BOTH INSIDE\n");
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recursive--;
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return;
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}
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// split the segment for each intersection with the
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// triangle segments and add it to the work queue.
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int intersections = 0;
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v3_t is[3] = {}; // 3d point of segment intercept
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v3_t it[3] = {}; // 3d point of triangle intercept
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for(int j = 0 ; j < 3 ; j++)
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{
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float ratio = hidden_intersect(
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&s->p[0], &s->p[1],
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&t->p[j], &t->p[(j+1)%3],
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&is[intersections],
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&it[intersections]
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);
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if (ratio < 0)
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continue;
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if (tri_debug >= 2)
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fprintf(stderr, "%d ratio=%.2f\n", j, ratio);
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intersections++;
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}
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// if none of them intersect, we keep looking
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if (intersections == 0)
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continue;
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if (tri_debug >= 2)
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fprintf(stderr, "%d intersections\n", intersections);
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if (intersections == 3)
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{
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// this likely means that the triangle is very, very
|
||||
// small, so let's just ignore this triangle
|
||||
if (tri_debug >= 2)
|
||||
fprintf(stderr, "Three intersections\n");
|
||||
continue;
|
||||
}
|
||||
|
||||
|
||||
if (intersections == 2)
|
||||
{
|
||||
// figure out how far it is to each of the intersections
|
||||
const float d00 = v3_len(&s->p[0], &is[0]);
|
||||
const float d01 = v3_len(&s->p[0], &is[1]);
|
||||
const float d10 = v3_len(&s->p[1], &is[0]);
|
||||
const float d11 = v3_len(&s->p[1], &is[1]);
|
||||
|
||||
if (tri_debug >= 2)
|
||||
fprintf(stderr, "Two intersections\n");
|
||||
|
||||
// discard segments that have two interesections that match
|
||||
// the segment exactly (distance from segment ends to
|
||||
// intersection point close enough to zero).
|
||||
if (d00 < EPS && d11 < EPS)
|
||||
{
|
||||
recursive--;
|
||||
return;
|
||||
}
|
||||
if (d01 < EPS && d10 < EPS)
|
||||
{
|
||||
recursive--;
|
||||
return;
|
||||
}
|
||||
|
||||
// if the segment intersection is closer than the triangle,
|
||||
// then we do nothing. degenerate cases are not handled
|
||||
if (d00 <= d01
|
||||
&& is[0].p[2] <= it[0].p[2]
|
||||
&& is[1].p[2] <= it[1].p[2])
|
||||
continue;
|
||||
if (d00 > d01
|
||||
&& is[1].p[2] <= it[0].p[2]
|
||||
&& is[0].p[2] <= it[1].p[2])
|
||||
continue;
|
||||
|
||||
// segment is behind the triangle,
|
||||
// we have to create a new segment
|
||||
// and shorten the existing segment
|
||||
// find the two intersections that we have
|
||||
// update the src field
|
||||
|
||||
// we need to create a new segment
|
||||
seg_t * news;
|
||||
if (d00 < d01)
|
||||
{
|
||||
// split from p0 to ix0
|
||||
news = seg_new(s->p[0], is[0]);
|
||||
news->src[0] = s->src[0];
|
||||
news->src[1] = s->src[1];
|
||||
s->p[0] = is[1];
|
||||
} else {
|
||||
// split from p0 to ix1
|
||||
news = seg_new(s->p[0], is[1]);
|
||||
news->src[0] = s->src[0];
|
||||
news->src[1] = s->src[1];
|
||||
s->p[0] = is[0];
|
||||
}
|
||||
|
||||
// recursively start splitting the new segment
|
||||
// starting at the next triangle down the z-depth
|
||||
tri_seg_intersect(zlist->next, news, slist_visible);
|
||||
|
||||
// continue splitting our current segment
|
||||
continue;
|
||||
}
|
||||
|
||||
if (intersections == 1)
|
||||
{
|
||||
// if there is an intersection, but the segment intercept
|
||||
// is closer than the triangle intercept, then no problem.
|
||||
// we do not bother with degenerate cases of intersecting
|
||||
// triangles
|
||||
if (is[0].p[2] <= it[0].p[2]
|
||||
&& is[1].p[2] <= it[0].p[2])
|
||||
{
|
||||
//svg_line("#00FF00", s->p[0].p, s->p[1].p, 10);
|
||||
continue;
|
||||
}
|
||||
|
||||
if (inside0)
|
||||
{
|
||||
// shorten it on the 0 side
|
||||
s->p[0] = is[0];
|
||||
// huh? shouldn't we process this one?
|
||||
return;
|
||||
continue;
|
||||
} else
|
||||
if (inside1)
|
||||
{
|
||||
// shorten it on the 1 side
|
||||
s->p[1] = is[0];
|
||||
// huh? shouldn't we process this one?
|
||||
return;
|
||||
continue;
|
||||
} else {
|
||||
// both outside, but an intersection?
|
||||
// split at that point and hope for the best
|
||||
seg_t * const news = seg_new(s->p[0], is[0]);
|
||||
news->src[0] = s->src[0];
|
||||
news->src[1] = s->src[1];
|
||||
s->p[0] = is[0];
|
||||
|
||||
tri_seg_intersect(zlist->next, news, slist_visible);
|
||||
// continue splitting our current segment
|
||||
continue;
|
||||
}
|
||||
}
|
||||
|
||||
next_segment:
|
||||
continue;
|
||||
}
|
||||
|
||||
// if we've reached here the segment is visible
|
||||
// and should be added to the visible list
|
||||
s->next = *slist_visible;
|
||||
*slist_visible = s;
|
||||
recursive--;
|
||||
}
|
||||
|
||||
|
||||
/*
|
||||
* Fast check to see if t2 is entire occluded by t.
|
||||
*/
|
||||
int
|
||||
tri_behind(
|
||||
const tri_t * const t,
|
||||
const tri_t * const t2
|
||||
)
|
||||
{
|
||||
float z0, z1, z2;
|
||||
int inside0 = tri_find_z(t, &t2->p[0], &z0);
|
||||
int inside1 = tri_find_z(t, &t2->p[1], &z1);
|
||||
int inside2 = tri_find_z(t, &t2->p[2], &z2);
|
||||
|
||||
// easy check -- if none of the points are inside,
|
||||
// t2 is not entirely occluded
|
||||
if (!inside0 || !inside1 || !inside2)
|
||||
return 0;
|
||||
|
||||
// are all of the intersection points ahead of t2?
|
||||
int behind0 = t2->p[0].p[2] >= z0;
|
||||
int behind1 = t2->p[1].p[2] >= z1;
|
||||
int behind2 = t2->p[2].p[2] >= z2;
|
||||
if (behind0 && behind1 && behind2)
|
||||
return 1;
|
||||
|
||||
// it is a STL violation if they are not all on the
|
||||
// same side (this would indicate that t and t2 intersect
|
||||
// go ahead and prune since it will cause problems
|
||||
if (behind0 || behind1 || behind2)
|
||||
{
|
||||
/*
|
||||
fprintf(stderr, "WARNING: triangles intersect %.0f %.0f %.0f inside %d %d %d behind %d %d %d\n", z0, z1, z2, inside0, inside1, inside2, behind0, behind1, behind2);
|
||||
tri_print(t);
|
||||
tri_print(t2);
|
||||
*/
|
||||
return 1;
|
||||
}
|
||||
|
||||
// they are all on the same side
|
||||
return 0;
|
||||
}
|
||||
507
tri.h
507
tri.h
@ -7,6 +7,7 @@
|
||||
#include "v3.h"
|
||||
#include "seg.h"
|
||||
|
||||
extern int tri_debug;
|
||||
|
||||
typedef struct _tri_t tri_t;
|
||||
struct _tri_t
|
||||
@ -21,39 +22,11 @@ struct _tri_t
|
||||
};
|
||||
|
||||
|
||||
|
||||
tri_t *
|
||||
tri_new(
|
||||
const v3_t * p_cam,
|
||||
const v3_t * p_xyz
|
||||
)
|
||||
{
|
||||
tri_t * const t = calloc(1, sizeof(*t));
|
||||
if (!t)
|
||||
return NULL;
|
||||
for(int i = 0 ; i < 3 ; i++)
|
||||
t->p[i] = p_cam[i];
|
||||
|
||||
// precompute the normals
|
||||
t->normal = v3_norm(v3_cross(
|
||||
v3_sub(t->p[1], t->p[0]),
|
||||
v3_sub(t->p[2], t->p[1])
|
||||
));
|
||||
t->normal_xyz = v3_norm(v3_cross(
|
||||
v3_sub(p_xyz[1], p_xyz[0]),
|
||||
v3_sub(p_xyz[2], p_xyz[1])
|
||||
));
|
||||
|
||||
|
||||
// compute the bounding box for the triangle in camera space
|
||||
for(int j = 0 ; j < 3 ; j++)
|
||||
{
|
||||
t->min[j] = min(min(t->p[0].p[j], t->p[1].p[j]), t->p[2].p[j]);
|
||||
t->max[j] = max(max(t->p[0].p[j], t->p[1].p[j]), t->p[2].p[j]);
|
||||
}
|
||||
|
||||
return t;
|
||||
}
|
||||
);
|
||||
|
||||
|
||||
// insert a triangle into our z-sorted list
|
||||
@ -61,44 +34,11 @@ void
|
||||
tri_insert(
|
||||
tri_t ** zlist,
|
||||
tri_t * t
|
||||
)
|
||||
{
|
||||
while(1)
|
||||
{
|
||||
tri_t * const iter = *zlist;
|
||||
if (!iter)
|
||||
break;
|
||||
|
||||
// check to see if our new triangle is closer than
|
||||
// the current triangle
|
||||
if(iter->min[2] > t->min[2])
|
||||
break;
|
||||
|
||||
zlist = &(iter->next);
|
||||
}
|
||||
|
||||
// either we reached the end of the list,
|
||||
// or we have found where our new triangle is sorted
|
||||
t->next = *zlist;
|
||||
t->prev = zlist;
|
||||
*zlist = t;
|
||||
if (t->next)
|
||||
t->next->prev = &t->next;
|
||||
}
|
||||
);
|
||||
|
||||
|
||||
void
|
||||
tri_delete(tri_t * t)
|
||||
{
|
||||
if (t->next)
|
||||
t->next->prev = t->prev;
|
||||
if (t->prev)
|
||||
*(t->prev) = t->next;
|
||||
|
||||
t->next = NULL;
|
||||
t->prev = NULL;
|
||||
free(t);
|
||||
}
|
||||
tri_delete(tri_t * t);
|
||||
|
||||
|
||||
// Compute the 2D area of a triangle in screen space
|
||||
@ -106,37 +46,13 @@ tri_delete(tri_t * t)
|
||||
float
|
||||
tri_area_2d(
|
||||
const tri_t * const t
|
||||
)
|
||||
{
|
||||
const float a = v3_dist_2d(&t->p[0], &t->p[1]);
|
||||
const float b = v3_dist_2d(&t->p[1], &t->p[2]);
|
||||
const float c = v3_dist_2d(&t->p[2], &t->p[0]);
|
||||
const float s = (a + b + c) / 2;
|
||||
|
||||
return sqrt(s * (s-a) * (s-b) * (s-c));
|
||||
}
|
||||
);
|
||||
|
||||
|
||||
void
|
||||
tri_print(
|
||||
const tri_t * const t
|
||||
)
|
||||
{
|
||||
fprintf(stderr, "%.0f,%.0f,%.0f %.0f,%.0f,%.0f %.0f,%.0f,%.0f norm %.3f,%.3f,%.3f\n",
|
||||
t->p[0].p[0],
|
||||
t->p[0].p[1],
|
||||
t->p[0].p[2],
|
||||
t->p[1].p[0],
|
||||
t->p[1].p[1],
|
||||
t->p[1].p[2],
|
||||
t->p[2].p[0],
|
||||
t->p[2].p[1],
|
||||
t->p[2].p[2],
|
||||
t->normal.p[0],
|
||||
t->normal.p[1],
|
||||
t->normal.p[2]
|
||||
);
|
||||
}
|
||||
|
||||
|
||||
/* Check if two triangles are coplanar and share an edge.
|
||||
@ -148,41 +64,7 @@ tri_coplanar(
|
||||
const tri_t * const t0,
|
||||
const tri_t * const t1,
|
||||
const float coplanar_eps
|
||||
)
|
||||
{
|
||||
// the two normals must be parallel-enough
|
||||
const float angle = v3_mag(v3_sub(t0->normal_xyz, t1->normal_xyz));
|
||||
if (angle < -coplanar_eps || +coplanar_eps < angle)
|
||||
return -1;
|
||||
|
||||
// find if there are two points shared
|
||||
unsigned matches = 0;
|
||||
for(int i = 0 ; i < 3 ; i++)
|
||||
{
|
||||
for(int j = 0 ; j < 3 ; j++)
|
||||
{
|
||||
if (!v3_eq(&t0->p[i], &t1->p[j]))
|
||||
continue;
|
||||
matches |= 1 << i;
|
||||
break;
|
||||
}
|
||||
}
|
||||
|
||||
switch(matches)
|
||||
{
|
||||
case 0x3: return 0;
|
||||
case 0x6: return 1;
|
||||
case 0x5: return 2;
|
||||
case 0x7:
|
||||
fprintf(stderr, "uh, three points match?\n");
|
||||
tri_print(t0);
|
||||
tri_print(t1);
|
||||
return -1;
|
||||
default:
|
||||
// no shared edge
|
||||
return -1;
|
||||
}
|
||||
}
|
||||
);
|
||||
|
||||
|
||||
/*
|
||||
@ -201,27 +83,7 @@ tri_find_z(
|
||||
const tri_t * const t,
|
||||
const v3_t * const p,
|
||||
float * const zout
|
||||
)
|
||||
{
|
||||
const float t1x = t->p[1].p[0] - t->p[0].p[0];
|
||||
const float t1y = t->p[1].p[1] - t->p[0].p[1];
|
||||
const float t1z = t->p[1].p[2] - t->p[0].p[2];
|
||||
const float t2x = t->p[2].p[0] - t->p[0].p[0];
|
||||
const float t2y = t->p[2].p[1] - t->p[0].p[1];
|
||||
const float t2z = t->p[2].p[2] - t->p[0].p[2];
|
||||
const float px = p->p[0] - t->p[0].p[0];
|
||||
const float py = p->p[1] - t->p[0].p[1];
|
||||
|
||||
const float a = (px * t2y - py * t2x) / (t1x * t2y - t2x * t1y);
|
||||
const float b = (px * t1y - py * t1x) / (t2x * t1y - t1x * t2y);
|
||||
|
||||
const float z = t->p[0].p[2] + a * t1z + b * t2z;
|
||||
|
||||
if (zout)
|
||||
*zout = z;
|
||||
|
||||
return 0 <= a && 0 <= b && a + b <= 1;
|
||||
}
|
||||
);
|
||||
|
||||
|
||||
/** Compute the points of intersection for two segments in 2d, and z points.
|
||||
@ -242,80 +104,8 @@ hidden_intersect(
|
||||
const v3_t * const p3,
|
||||
v3_t * const l0_int,
|
||||
v3_t * const l1_int
|
||||
)
|
||||
{
|
||||
const float p0_x = p0->p[0];
|
||||
const float p0_y = p0->p[1];
|
||||
const float p0_z = p0->p[2];
|
||||
const float p1_x = p1->p[0];
|
||||
const float p1_y = p1->p[1];
|
||||
const float p1_z = p1->p[2];
|
||||
const float p2_x = p2->p[0];
|
||||
const float p2_y = p2->p[1];
|
||||
const float p2_z = p2->p[2];
|
||||
const float p3_x = p3->p[0];
|
||||
const float p3_y = p3->p[1];
|
||||
const float p3_z = p3->p[2];
|
||||
|
||||
const float s1_x = p1_x - p0_x;
|
||||
const float s1_y = p1_y - p0_y;
|
||||
const float s2_x = p3_x - p2_x;
|
||||
const float s2_y = p3_y - p2_y;
|
||||
|
||||
// compute r x s
|
||||
const float d = -s2_x * s1_y + s1_x * s2_y;
|
||||
|
||||
// if they are close to parallel, then we do not need to check
|
||||
// for intersection (we define that as "non-intersecting")
|
||||
if (-EPS < d && d < EPS)
|
||||
return -1;
|
||||
|
||||
// Compute how far along each line they would interesect
|
||||
const float r0 = ( s2_x * (p0_y - p2_y) - s2_y * (p0_x - p2_x)) / d;
|
||||
const float r1 = (-s1_y * (p0_x - p2_x) + s1_x * (p0_y - p2_y)) / d;
|
||||
|
||||
// if they are not within the ratio (0,1), then the intersecton occurs
|
||||
// outside of the segments and is not of concern
|
||||
if (r0 < 0 || r0 > 1)
|
||||
return -1;
|
||||
if (r1 < 0 || r1 > 1)
|
||||
return -1;
|
||||
|
||||
// Collision detected with the segments
|
||||
if(0) fprintf(stderr, "collision: %.0f,%.0f,%.0f->%.0f,%.0f,%.0f %.0f,%.0f,%.0f->%.0f,%.0f,%.0f == %.3f,%.3f\n",
|
||||
p0_x, p0_y, p0_z,
|
||||
p1_x, p1_y, p1_z,
|
||||
p2_x, p2_y, p2_z,
|
||||
p3_x, p3_y, p2_z,
|
||||
r0,
|
||||
r1
|
||||
);
|
||||
|
||||
const float ix = p0_x + (r0 * s1_x);
|
||||
const float iy = p0_y + (r0 * s1_y);
|
||||
|
||||
// compute the z intercept for each on the two different coordinates
|
||||
if(l0_int)
|
||||
{
|
||||
*l0_int = (v3_t){{
|
||||
ix,
|
||||
iy,
|
||||
p0_z + r0 * (p1_z - p0_z)
|
||||
}};
|
||||
}
|
||||
|
||||
if(l1_int)
|
||||
{
|
||||
*l1_int = (v3_t){{
|
||||
ix,
|
||||
iy,
|
||||
p2_z + r1 * (p3_z - p2_z)
|
||||
}};
|
||||
}
|
||||
|
||||
return r0;
|
||||
}
|
||||
|
||||
|
||||
/*
|
||||
* Recursive algorithm:
|
||||
@ -332,255 +122,8 @@ tri_seg_intersect(
|
||||
const tri_t * zlist,
|
||||
seg_t * s,
|
||||
seg_t ** slist_visible
|
||||
)
|
||||
{
|
||||
const float p0z = s->p[0].p[2];
|
||||
const float p1z = s->p[1].p[2];
|
||||
const float seg_max_z = max(p0z, p1z);
|
||||
|
||||
// avoid processing empty segments
|
||||
const float seg_len = v3_len(&s->p[0], &s->p[1]);
|
||||
if (seg_len < EPS)
|
||||
return;
|
||||
|
||||
static int recursive;
|
||||
recursive++;
|
||||
|
||||
//fprintf(stderr, "%d: processing segment ", recursive); seg_print(s);
|
||||
fprintf(stderr, "--- recursive %d\n", recursive);
|
||||
seg_print(s);
|
||||
|
||||
for( const tri_t * t = zlist ; t ; t = t->next )
|
||||
{
|
||||
// if the segment is closer than the triangle,
|
||||
// then we no longer have to check any further into
|
||||
// the zlist (it is sorted by depth).
|
||||
if (seg_max_z <= t->min[2])
|
||||
break;
|
||||
|
||||
#if 0
|
||||
// make sure that we're not comparing to our own triangle
|
||||
// or one that shares an edge with us (which might be in
|
||||
// a different order)
|
||||
if (v2_eq(s->src[0].p, t->p[0].p, 0.0005)
|
||||
&& v2_eq(s->src[1].p, t->p[1].p, 0.0005))
|
||||
continue;
|
||||
if (v2_eq(s->src[0].p, t->p[1].p, 0.0005)
|
||||
&& v2_eq(s->src[1].p, t->p[2].p, 0.0005))
|
||||
continue;
|
||||
if (v2_eq(s->src[0].p, t->p[2].p, 0.0005)
|
||||
&& v2_eq(s->src[1].p, t->p[0].p, 0.0005))
|
||||
continue;
|
||||
if (v2_eq(s->src[0].p, t->p[1].p, 0.0005)
|
||||
&& v2_eq(s->src[1].p, t->p[0].p, 0.0005))
|
||||
continue;
|
||||
if (v2_eq(s->src[0].p, t->p[2].p, 0.0005)
|
||||
&& v2_eq(s->src[1].p, t->p[1].p, 0.0005))
|
||||
continue;
|
||||
if (v2_eq(s->src[0].p, t->p[0].p, 0.0005)
|
||||
&& v2_eq(s->src[1].p, t->p[2].p, 0.0005))
|
||||
continue;
|
||||
#endif
|
||||
|
||||
if (debug >= 2)
|
||||
tri_print(t);
|
||||
/*
|
||||
// if the segment is co-linear to any of the
|
||||
// triangle edges, include it
|
||||
for(int i = 0 ; i < 3 ; i++)
|
||||
{
|
||||
if (parallel(
|
||||
&s->p[0], &s->p[1],
|
||||
&t->p[i], &t->p[(i+1)%3]
|
||||
))
|
||||
goto next_segment;
|
||||
}
|
||||
*/
|
||||
|
||||
float z0, z1;
|
||||
int inside0 = tri_find_z(t, &s->p[0], &z0);
|
||||
int inside1 = tri_find_z(t, &s->p[1], &z1);
|
||||
|
||||
if (debug >= 2 && (inside0 || inside1))
|
||||
{
|
||||
fprintf(stderr, "inside %d %d\n", inside0, inside1);
|
||||
}
|
||||
|
||||
// if both are inside but the segment is infront of the
|
||||
// triangle, then we retain the segment.
|
||||
// otherwies we discard the segment
|
||||
if (inside0 && inside1)
|
||||
{
|
||||
if (s->p[0].p[2] <= z0
|
||||
&& s->p[1].p[2] <= z1)
|
||||
continue;
|
||||
if (debug >= 2)
|
||||
fprintf(stderr, "BOTH INSIDE\n");
|
||||
recursive--;
|
||||
return;
|
||||
}
|
||||
|
||||
// split the segment for each intersection with the
|
||||
// triangle segments and add it to the work queue.
|
||||
int intersections = 0;
|
||||
v3_t is[3] = {}; // 3d point of segment intercept
|
||||
v3_t it[3] = {}; // 3d point of triangle intercept
|
||||
|
||||
for(int j = 0 ; j < 3 ; j++)
|
||||
{
|
||||
float ratio = hidden_intersect(
|
||||
&s->p[0], &s->p[1],
|
||||
&t->p[j], &t->p[(j+1)%3],
|
||||
&is[intersections],
|
||||
&it[intersections]
|
||||
);
|
||||
|
||||
if (ratio < 0)
|
||||
continue;
|
||||
|
||||
if (debug >= 2)
|
||||
fprintf(stderr, "%d ratio=%.2f\n", j, ratio);
|
||||
intersections++;
|
||||
}
|
||||
|
||||
|
||||
// if none of them intersect, we keep looking
|
||||
if (intersections == 0)
|
||||
continue;
|
||||
|
||||
if (debug >= 2)
|
||||
fprintf(stderr, "%d intersections\n", intersections);
|
||||
|
||||
if (intersections == 3)
|
||||
{
|
||||
// this likely means that the triangle is very, very
|
||||
// small, so let's just ignore this triangle
|
||||
if (debug >= 2)
|
||||
fprintf(stderr, "Three intersections\n");
|
||||
continue;
|
||||
}
|
||||
|
||||
|
||||
if (intersections == 2)
|
||||
{
|
||||
// figure out how far it is to each of the intersections
|
||||
const float d00 = v3_len(&s->p[0], &is[0]);
|
||||
const float d01 = v3_len(&s->p[0], &is[1]);
|
||||
const float d10 = v3_len(&s->p[1], &is[0]);
|
||||
const float d11 = v3_len(&s->p[1], &is[1]);
|
||||
|
||||
if (debug >= 2)
|
||||
fprintf(stderr, "Two intersections\n");
|
||||
|
||||
// discard segments that have two interesections that match
|
||||
// the segment exactly (distance from segment ends to
|
||||
// intersection point close enough to zero).
|
||||
if (d00 < EPS && d11 < EPS)
|
||||
{
|
||||
recursive--;
|
||||
return;
|
||||
}
|
||||
if (d01 < EPS && d10 < EPS)
|
||||
{
|
||||
recursive--;
|
||||
return;
|
||||
}
|
||||
|
||||
// if the segment intersection is closer than the triangle,
|
||||
// then we do nothing. degenerate cases are not handled
|
||||
if (d00 <= d01
|
||||
&& is[0].p[2] <= it[0].p[2]
|
||||
&& is[1].p[2] <= it[1].p[2])
|
||||
continue;
|
||||
if (d00 > d01
|
||||
&& is[1].p[2] <= it[0].p[2]
|
||||
&& is[0].p[2] <= it[1].p[2])
|
||||
continue;
|
||||
|
||||
// segment is behind the triangle,
|
||||
// we have to create a new segment
|
||||
// and shorten the existing segment
|
||||
// find the two intersections that we have
|
||||
// update the src field
|
||||
|
||||
// we need to create a new segment
|
||||
seg_t * news;
|
||||
if (d00 < d01)
|
||||
{
|
||||
// split from p0 to ix0
|
||||
news = seg_new(s->p[0], is[0]);
|
||||
news->src[0] = s->src[0];
|
||||
news->src[1] = s->src[1];
|
||||
s->p[0] = is[1];
|
||||
} else {
|
||||
// split from p0 to ix1
|
||||
news = seg_new(s->p[0], is[1]);
|
||||
news->src[0] = s->src[0];
|
||||
news->src[1] = s->src[1];
|
||||
s->p[0] = is[0];
|
||||
}
|
||||
|
||||
// recursively start splitting the new segment
|
||||
// starting at the next triangle down the z-depth
|
||||
tri_seg_intersect(zlist->next, news, slist_visible);
|
||||
|
||||
// continue splitting our current segment
|
||||
continue;
|
||||
}
|
||||
|
||||
if (intersections == 1)
|
||||
{
|
||||
// if there is an intersection, but the segment intercept
|
||||
// is closer than the triangle intercept, then no problem.
|
||||
// we do not bother with degenerate cases of intersecting
|
||||
// triangles
|
||||
if (is[0].p[2] <= it[0].p[2]
|
||||
&& is[1].p[2] <= it[0].p[2])
|
||||
{
|
||||
//svg_line("#00FF00", s->p[0].p, s->p[1].p, 10);
|
||||
continue;
|
||||
}
|
||||
|
||||
if (inside0)
|
||||
{
|
||||
// shorten it on the 0 side
|
||||
s->p[0] = is[0];
|
||||
// huh? shouldn't we process this one?
|
||||
return;
|
||||
continue;
|
||||
} else
|
||||
if (inside1)
|
||||
{
|
||||
// shorten it on the 1 side
|
||||
s->p[1] = is[0];
|
||||
// huh? shouldn't we process this one?
|
||||
return;
|
||||
continue;
|
||||
} else {
|
||||
// both outside, but an intersection?
|
||||
// split at that point and hope for the best
|
||||
seg_t * const news = seg_new(s->p[0], is[0]);
|
||||
news->src[0] = s->src[0];
|
||||
news->src[1] = s->src[1];
|
||||
s->p[0] = is[0];
|
||||
|
||||
tri_seg_intersect(zlist->next, news, slist_visible);
|
||||
// continue splitting our current segment
|
||||
continue;
|
||||
}
|
||||
}
|
||||
|
||||
next_segment:
|
||||
continue;
|
||||
}
|
||||
|
||||
// if we've reached here the segment is visible
|
||||
// and should be added to the visible list
|
||||
s->next = *slist_visible;
|
||||
*slist_visible = s;
|
||||
recursive--;
|
||||
}
|
||||
|
||||
|
||||
/*
|
||||
* Fast check to see if t2 is entire occluded by t.
|
||||
@ -589,40 +132,6 @@ int
|
||||
tri_behind(
|
||||
const tri_t * const t,
|
||||
const tri_t * const t2
|
||||
)
|
||||
{
|
||||
float z0, z1, z2;
|
||||
int inside0 = tri_find_z(t, &t2->p[0], &z0);
|
||||
int inside1 = tri_find_z(t, &t2->p[1], &z1);
|
||||
int inside2 = tri_find_z(t, &t2->p[2], &z2);
|
||||
|
||||
// easy check -- if none of the points are inside,
|
||||
// t2 is not entirely occluded
|
||||
if (!inside0 || !inside1 || !inside2)
|
||||
return 0;
|
||||
|
||||
// are all of the intersection points ahead of t2?
|
||||
int behind0 = t2->p[0].p[2] >= z0;
|
||||
int behind1 = t2->p[1].p[2] >= z1;
|
||||
int behind2 = t2->p[2].p[2] >= z2;
|
||||
if (behind0 && behind1 && behind2)
|
||||
return 1;
|
||||
|
||||
// it is a STL violation if they are not all on the
|
||||
// same side (this would indicate that t and t2 intersect
|
||||
// go ahead and prune since it will cause problems
|
||||
if (behind0 || behind1 || behind2)
|
||||
{
|
||||
/*
|
||||
fprintf(stderr, "WARNING: triangles intersect %.0f %.0f %.0f inside %d %d %d behind %d %d %d\n", z0, z1, z2, inside0, inside1, inside2, behind0, behind1, behind2);
|
||||
tri_print(t);
|
||||
tri_print(t2);
|
||||
*/
|
||||
return 1;
|
||||
}
|
||||
|
||||
// they are all on the same side
|
||||
return 0;
|
||||
}
|
||||
);
|
||||
|
||||
#endif
|
||||
|
||||
Loading…
Reference in New Issue
Block a user