lots of hacks, but it is starting to work
This commit is contained in:
Trammell hudson
parent
d321a1e86d
commit
ae46476d09
373
hiddenwire.c
373
hiddenwire.c
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@ -49,12 +49,9 @@ struct _tri_t
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};
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// line segment has to track its source so that it knows which to not
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// compare against in its occlusion checks.
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typedef struct _seg_t seg_t;
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struct _seg_t {
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v3_t p[2];
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v3_t src[2];
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seg_t * next;
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};
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@ -242,15 +239,16 @@ static float poly_min[2], poly_max[2];
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static inline int
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v2_eq(
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const float p0[],
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const float p1[]
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const float p1[],
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const float eps
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)
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{
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const float dx = p0[0] - p1[0];
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const float dy = p0[1] - p1[1];
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// are the points within epsilon of each other?
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if (-EPS < dx && dx < EPS
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&& -EPS < dy && dy < EPS)
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if (-eps < dx && dx < eps
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&& -eps < dy && dy < eps)
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return 1;
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// nope, not equal
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@ -299,7 +297,7 @@ get_line_intersection(
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if (s > EPS && s < 1-EPS && t > EPS && t < 1-EPS)
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{
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if(0) fprintf(stderr, "collision: %f,%f->%f,%f %f,%f->%f,%f == %f,%f\n",
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if(1) fprintf(stderr, "collision: %f,%f->%f,%f %f,%f->%f,%f == %f,%f\n",
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p0_x, p0_y,
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p1_x, p1_y,
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p2_x, p2_y,
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@ -320,30 +318,96 @@ get_line_intersection(
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}
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int
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intersect(
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const v3_t * const p00,
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const v3_t * const p01,
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const v3_t * const p10,
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const v3_t * const p11,
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float *px,
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float *py
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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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// special case; if this is the same line, it does not intersect
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if (v2_eq(p00->p, p10->p) && v2_eq(p01->p, p11->p))
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return 0;
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if (v2_eq(p01->p, p10->p) && v2_eq(p00->p, p11->p))
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return 0;
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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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return get_line_intersection(
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p00->p[0], p00->p[1],
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p01->p[0], p01->p[1],
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p10->p[0], p10->p[1],
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p11->p[0], p11->p[1],
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px,
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py
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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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@ -924,14 +988,79 @@ seg_new(
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return NULL;
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s->p[0] = p0;
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s->p[1] = p1;
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s->src[0] = p0;
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s->src[1] = p1;
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s->next = NULL;
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return s;
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}
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void
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seg_print(
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const seg_t * const s
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)
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{
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fprintf(stderr, "%.0f,%.0f -> %.0f,%.0f\n",
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s->p[0].p[0],
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s->p[0].p[1],
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s->p[1].p[0],
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s->p[1].p[1]
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);
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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\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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);
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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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*/
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float
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find_z(
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const v3_t * const p0,
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const v3_t * const p1,
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const float x,
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const float y
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)
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{
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const float dx = p1->p[0] - p0->p[0];
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const float dy = p1->p[1] - p0->p[1];
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const float dz = p1->p[2] - p0->p[2];
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// find the z value of the intersection point
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// on the segment. we don't care about the triangle
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float ratio = 0;
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if (dx != 0)
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{
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ratio = (x - p0->p[0]) / dx;
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} else
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if (dy != 0)
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{
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ratio = (y - p0->p[1]) / dy;
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} else {
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fprintf(stderr, "uh, dx and dy both zero?\n");
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return -1;
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}
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return p0->p[2] + dz * ratio;
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}
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/*
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int
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tri_line_intersect(
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@ -967,22 +1096,41 @@ tri_seg_intersect(
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seg_t ** slist_visible
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)
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{
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const float p0x = s->p[0].p[0];
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const float p0y = s->p[0].p[1];
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const float p0z = s->p[0].p[2];
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const float p1x = s->p[1].p[0];
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const float p1y = s->p[1].p[1];
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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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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 (p0z < t->min[2] && p1z < t->min[2])
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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, 0.1)
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&& v2_eq(s->src[1].p, t->p[1].p, 0.1))
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continue;
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if (v2_eq(s->src[0].p, t->p[1].p, 0.1)
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&& v2_eq(s->src[1].p, t->p[2].p, 0.1))
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continue;
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if (v2_eq(s->src[0].p, t->p[2].p, 0.1)
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&& v2_eq(s->src[1].p, t->p[0].p, 0.1))
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continue;
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if (v2_eq(s->src[0].p, t->p[1].p, 0.1)
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&& v2_eq(s->src[1].p, t->p[0].p, 0.1))
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continue;
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if (v2_eq(s->src[0].p, t->p[2].p, 0.1)
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&& v2_eq(s->src[1].p, t->p[1].p, 0.1))
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continue;
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if (v2_eq(s->src[0].p, t->p[0].p, 0.1)
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&& v2_eq(s->src[1].p, t->p[2].p, 0.1))
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continue;
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// do a quick test of does this segment even comes
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// close to this triangle
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if (p0x < t->min[0] && p1x < t->min[0]
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@ -1012,27 +1160,49 @@ tri_seg_intersect(
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// if both are inside we discard this segment
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if (inside0 && inside1)
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{
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//svg_line("#0000FF", s->p[0].p, s->p[1].p, 0);
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//svg_line("#00FF00", t->p[0].p, t->p[1].p, 0);
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//svg_line("#00FF00", t->p[1].p, t->p[2].p, 0);
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//svg_line("#00FF00", t->p[2].p, t->p[0].p, 0);
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fprintf(stderr, "BOTH INSIDE\n");
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tri_print(t);
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seg_print(s);
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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 ix[3] = {};
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const float max_z = max(s->p[0].p[2], s->p[1].p[2]);
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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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ix[j].p[2] = max_z;
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int rc = intersect(
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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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&ix[intersections].p[0], &ix[intersections].p[1]
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&is[intersections],
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&it[intersections]
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);
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if (!rc)
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if (ratio < 0)
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continue;
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intersections++;
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// deal with corner cases where the segment
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// exactly lines up with the triangle edge
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// we do not treat this as an intersection
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if (-EPS < ratio && ratio < EPS)
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{
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inside0 = 0;
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} else
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if (1-EPS < ratio && ratio < 1+EPS)
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{
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inside1 = 0;
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} else {
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// this is a real intersection
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intersections++;
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}
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}
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// if none of them intersect, we keep looking
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@ -1051,31 +1221,46 @@ fprintf(stderr, "split %d %d inter %d\n", inside0 , inside1, intersections);
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if (inside0 || inside1)
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{
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fprintf(stderr, "uh, inside but two intersections?\n");
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return;
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//return;
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}
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// if the segment intersection is closer than the triangle,
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// then we do nothing. degenerate cases are not handled
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if (is[0].p[2] <= it[0].p[2]
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|| is[1].p[2] <= it[1].p[2])
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{
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fprintf(stderr, "ignoring collision since z %f < %f || %f < %f\n",
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is[0].p[2], it[0].p[2],
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is[1].p[2], it[1].p[2]);
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continue;
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}
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// segment is behind the triangle,
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// we have to create a new segment
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// and shorten the existing segment
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// find the two intersections that we have
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// update the src field
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fprintf(stderr, "two intersections\n");
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const float d0 = v2_dist(s->p[0].p, ix[0].p);
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const float d1 = v2_dist(s->p[1].p, ix[0].p);
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const float d0 = v3_len(&s->p[0], &is[0]);
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const float d1 = v3_len(&s->p[0], &is[1]);
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fprintf(stderr, "two intersections %.0f %.0f\n", d0, d1);
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seg_t * news;
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if (d0 < d1)
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{
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// split from p0 to ix0
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news = seg_new(s->p[0], ix[0]);
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news->src[1] = s->p[1];
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s->p[1] = ix[1];
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news = seg_new(s->p[0], is[0]);
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s->p[0] = is[1];
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} else {
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// split from p0 to ix1
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news = seg_new(s->p[0], ix[1]);
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news->src[1] = s->p[1];
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s->p[1] = ix[0];
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news = seg_new(s->p[0], is[1]);
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s->p[0] = is[0];
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}
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fprintf(stderr, "old segment:" );
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seg_print(s);
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fprintf(stderr, "new segment:" );
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seg_print(news);
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// recursively start splitting the new segment
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// starting at our current z-depth
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@ -1087,36 +1272,47 @@ fprintf(stderr, "split %d %d inter %d\n", inside0 , inside1, intersections);
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if (intersections == 1)
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{
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fprintf(stderr, "split %d %d\n", inside0, inside1);
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// if there is an intersection, but the segment intercept
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// is close than the triangle intercept, then no problem.
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// we do not bother with degenerate cases of intersecting
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// triangles
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if (is[0].p[2] <= it[0].p[2])
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continue;
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// segment is behind the triangle, so it needs to be
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// cut into pieces
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if (inside0)
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{
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// shorten it on the 0 side
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s->p[0] = ix[0];
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s->p[0] = is[0];
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continue;
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} else
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if (inside1)
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{
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// shorten it on the 1 side
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s->p[1] = ix[0];
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s->p[1] = is[0];
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continue;
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} else
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if (v2_eq(s->p[0].p, is[0].p, 0.1))
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{
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// the 0 side is on the triangle, don't bother
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continue;
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} else
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if (v2_eq(s->p[1].p, is[0].p, 0.1))
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{
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// the 1 side is on the triangle, don't bother
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continue;
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} else {
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fprintf(stderr, "uh, both outside but one intersection?\n");
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return;
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fprintf(stderr, "uh, both outside but one intersection? %.3f,%.3f\n",
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is[0].p[0],
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is[0].p[1]
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);
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seg_print(s);
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tri_print(t);
|
||||
//svg_line("#00FF00", s->p[0].p, s->p[1].p, 0);
|
||||
continue;
|
||||
}
|
||||
}
|
||||
|
||||
|
||||
if(0) fprintf(stderr, "check: %.0f,%.0f -> %.0f,%.0f %.0f,%.0f %.0f,%.0f %.0f,%.0f\n",
|
||||
s->p[0].p[0],
|
||||
s->p[0].p[1],
|
||||
s->p[1].p[0],
|
||||
s->p[1].p[1],
|
||||
t->p[0].p[0],
|
||||
t->p[0].p[1],
|
||||
t->p[1].p[0],
|
||||
t->p[1].p[1],
|
||||
t->p[2].p[0],
|
||||
t->p[2].p[1]
|
||||
);
|
||||
//return;
|
||||
}
|
||||
|
||||
// if we've reached here the segment is visible
|
||||
|
|
@ -1141,6 +1337,13 @@ int main(
|
|||
char ** argv
|
||||
)
|
||||
{
|
||||
v3_t p0 = {{ 0, 0, 0 }};
|
||||
v3_t p1 = {{ 100, 100, 100 }};
|
||||
v3_t p2 = {{ 200, -100, 0 }};
|
||||
v3_t p3 = {{ 0, 100, 200 }};
|
||||
v3_t is, it;
|
||||
hidden_intersect(&p0, &p1, &p2, &p3, &is, &it);
|
||||
|
||||
const size_t max_len = 32 << 20;
|
||||
uint8_t * const buf = calloc(max_len, 1);
|
||||
|
||||
|
|
@ -1178,6 +1381,8 @@ int main(
|
|||
seg_t * slist = NULL;
|
||||
seg_t * slist_visible = NULL;
|
||||
|
||||
int retained = 0;
|
||||
|
||||
// transform the stl by the camera projection and generate
|
||||
// a z-sorted list of triangles
|
||||
for (int i = 0 ; i < num_triangles ; i++)
|
||||
|
|
@ -1212,6 +1417,10 @@ int main(
|
|||
slist = s;
|
||||
}
|
||||
|
||||
retained++;
|
||||
if( retained > 3)
|
||||
break;
|
||||
|
||||
continue;
|
||||
|
||||
reject:
|
||||
|
|
@ -1220,19 +1429,29 @@ reject:
|
|||
}
|
||||
|
||||
if (debug)
|
||||
fprintf(stderr, "Rejected %d triangles\n", rejected);
|
||||
fprintf(stderr, "Retained %d, rejected %d triangles\n", retained, rejected);
|
||||
|
||||
for( const tri_t * t = zlist ; t ; t = t->next )
|
||||
tri_print(t);
|
||||
|
||||
// we now have a z-sorted list of triangles
|
||||
rejected = 0;
|
||||
|
||||
// work on each segment, intersecting it with all of the triangles
|
||||
while(slist)
|
||||
if(1)
|
||||
{
|
||||
seg_t * s = slist;
|
||||
slist = s->next;
|
||||
// work on each segment, intersecting it with all of the triangles
|
||||
while(slist)
|
||||
{
|
||||
seg_t * s = slist;
|
||||
slist = s->next;
|
||||
|
||||
tri_seg_intersect(zlist, s, &slist_visible);
|
||||
tri_seg_intersect(zlist, s, &slist_visible);
|
||||
|
||||
}
|
||||
} else {
|
||||
// don't do any intersection tests
|
||||
slist_visible = slist;
|
||||
slist = NULL;
|
||||
}
|
||||
|
||||
// display all of the visible segments
|
||||
|
|
|
|||
Loading…
Reference in New Issue