1472 lines
29 KiB
C
1472 lines
29 KiB
C
/** \file
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* Render a hidden wireframe version of an STL file.
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*
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <stdint.h>
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#include <stdarg.h>
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#include <unistd.h>
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#include <math.h>
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#include <err.h>
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#include <assert.h>
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#include "v3.h"
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#include "camera.h"
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#ifndef M_PI
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#define M_PI 3.1415926535897932384
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#endif
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static int debug = 1;
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typedef struct
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{
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char header[80];
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uint32_t num_triangles;
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} __attribute__((__packed__))
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stl_header_t;
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typedef struct
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{
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v3_t normal;
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v3_t p[3];
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uint16_t attr;
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} __attribute__((__packed__))
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stl_face_t;
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typedef struct _tri_t tri_t;
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struct _tri_t
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{
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v3_t p[3];
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v3_t normal;
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float area;
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float min[3];
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float max[3];
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tri_t * next;
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tri_t ** prev;
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};
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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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seg_t * next;
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};
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#if 0
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typedef struct face face_t;
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typedef struct poly poly_t;
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struct face
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{
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float sides[3];
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face_t * next[3];
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int next_edge[3];
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int coplanar[3];
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int used;
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};
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// once this triangle has been used, it will be placed
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// in a polygon group and fixed in a position relative to that group
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struct poly
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{
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int start_edge;
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int printed;
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// local coordinates of the triangle vertices
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float a;
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float x2;
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float y2;
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float rot;
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// absolute coordintes of the triangle vertices
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float p[3][2];
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// todo: make this const and add backtracking
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face_t * face;
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poly_t * next[3];
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poly_t * work_next;
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};
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/* Compare two edges in two triangles.
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*
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* note that if the windings are all the same, the edges will
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* compare in the opposite order (for example, the edge from 0 to 1
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* compares to the edge from 2 to 1 in the other triangle).
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*/
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static int
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edge_eq2(
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const stl_face_t * const t0,
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const stl_face_t * const t1,
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int e0,
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int e1
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)
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{
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const v3_t * const v00 = &t0->p[e0];
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const v3_t * const v01 = &t0->p[(e0+1) % 3];
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const v3_t * const v10 = &t1->p[e1];
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const v3_t * const v11 = &t1->p[(e1+1) % 3];
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if (v3_eq(v00, v11) && v3_eq(v01, v10))
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return 1;
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return 0;
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}
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#endif
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void
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svg_line(
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const char * color,
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const float * p1,
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const float * p2,
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int dash
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)
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{
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if (!dash)
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{
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printf("<line x1=\"%f\" y1=\"%f\" x2=\"%f\" y2=\"%f\" stroke=\"%s\" stroke-width=\"0.5px\"/>\n",
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p1[0],
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p1[1],
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p2[0],
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p2[1],
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color
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);
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return;
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}
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// dashed line, split in the middle
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const float dx = p2[0] - p1[0];
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const float dy = p2[1] - p1[1];
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const float h1[] = {
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p1[0] + dx*0.45,
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p1[1] + dy*0.45,
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};
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const float h2[] = {
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p1[0] + dx*0.55,
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p1[1] + dy*0.55,
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};
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svg_line(color, p1, h1, 0);
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svg_line(color, h2, p2, 0);
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}
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#if 0
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void
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rotate(
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float * p,
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const float * origin,
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float a,
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float x,
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float y
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)
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{
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p[0] = cos(a) * x - sin(a) * y + origin[0];
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p[1] = sin(a) * x + cos(a) * y + origin[1];
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}
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/* Rotate and translate a triangle */
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void
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poly_position(
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poly_t * const g,
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const poly_t * const g_src,
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float rot,
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float trans_x,
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float trans_y
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)
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{
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const face_t * const f = g->face;
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const int start_edge = g->start_edge;
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float a = f->sides[(start_edge + 0) % 3];
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float c = f->sides[(start_edge + 1) % 3];
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float b = f->sides[(start_edge + 2) % 3];
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float x2 = (a*a + b*b - c*c) / (2*a);
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float y2 = sqrt(b*b - x2*x2);
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// translate by trans_x/trans_y in the original ref frame
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// to get the origin point
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float origin[2];
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rotate(origin, g_src->p[0], g_src->rot, trans_x, trans_y);
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g->rot = g_src->rot + rot;
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g->a = a;
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g->x2 = x2;
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g->y2 = y2;
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//fprintf(stderr, "%p %d %f %f %f %f => %f %f %f\n", f, start_edge, g->rot*180/M_PI, a, b, c, x2, y2, rot);
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rotate(g->p[0], origin, g->rot, 0, 0);
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rotate(g->p[1], origin, g->rot, a, 0);
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rotate(g->p[2], origin, g->rot, x2, y2);
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}
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static void
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enqueue(
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poly_t * g,
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poly_t * const new_g,
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int at_head
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)
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{
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if (at_head)
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{
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new_g->work_next = g->work_next;
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g->work_next = new_g;
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return;
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}
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// go to the end of the line
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while (g->work_next)
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g = g->work_next;
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g->work_next = new_g;
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}
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static poly_t * poly_root;
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static float poly_min[2], poly_max[2];
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#endif
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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 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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return 1;
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// nope, not equal
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return 0;
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}
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static inline int
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v2_dist(
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const float p0[],
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const float p1[]
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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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return sqrt(dx*dx + dy*dy);
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}
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// Returns 1 if the lines intersect, otherwise 0. In addition, if the lines
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// intersect the intersection point may be stored in the floats i_x and i_y.
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int
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get_line_intersection(
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float p0_x,
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float p0_y,
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float p1_x,
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float p1_y,
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float p2_x,
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float p2_y,
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float p3_x,
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float p3_y,
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float *i_x,
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float *i_y
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)
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{
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float s1_x = p1_x - p0_x;
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float s1_y = p1_y - p0_y;
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float s2_x = p3_x - p2_x;
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float s2_y = p3_y - p2_y;
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float s = (-s1_y * (p0_x - p2_x) + s1_x * (p0_y - p2_y))
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/ (-s2_x * s1_y + s1_x * s2_y);
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float t = ( s2_x * (p0_y - p2_y) - s2_y * (p0_x - p2_x))
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/ (-s2_x * s1_y + s1_x * s2_y);
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if (s > EPS && s < 1-EPS && t > EPS && t < 1-EPS)
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{
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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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p3_x, p3_y,
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s,
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t
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);
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// Collision detected
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if (i_x != NULL)
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*i_x = p0_x + (t * s1_x);
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if (i_y != NULL)
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*i_y = p0_y + (t * s1_y);
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return 1;
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}
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return 0; // No collision
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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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#if 0
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/** Check to see if two triangles overlap */
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int
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overlap_poly(
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const poly_t * const g1,
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const poly_t * const g2
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)
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{
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if (intersect(g1->p[0], g1->p[1], g2->p[0], g2->p[1]))
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return 1;
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if (intersect(g1->p[0], g1->p[1], g2->p[1], g2->p[2]))
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return 1;
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if (intersect(g1->p[0], g1->p[1], g2->p[2], g2->p[0]))
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return 1;
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if (intersect(g1->p[1], g1->p[2], g2->p[0], g2->p[1]))
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return 1;
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if (intersect(g1->p[1], g1->p[2], g2->p[1], g2->p[2]))
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return 1;
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if (intersect(g1->p[1], g1->p[2], g2->p[2], g2->p[0]))
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return 1;
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if (intersect(g1->p[2], g1->p[0], g2->p[0], g2->p[1]))
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return 1;
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if (intersect(g1->p[2], g1->p[0], g2->p[1], g2->p[2]))
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return 1;
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if (intersect(g1->p[2], g1->p[0], g2->p[2], g2->p[0]))
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return 1;
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return 0;
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}
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/** Check to see if any triangles overlap */
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int
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overlap_check(
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const poly_t * g,
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const poly_t * const new_g
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)
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{
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// special case -- if the root is the same as the one that we
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// are checking, then it does not overlap
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if (g == new_g)
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return 0;
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while (g)
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{
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if (overlap_poly(g, new_g))
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return 1;
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g = g->work_next;
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}
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return 0;
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}
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|
|
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/** recursively try to fix up the triangles.
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*
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* returns the maximum number of triangles added
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*/
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int
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poly_build(
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poly_t * const g
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)
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{
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face_t * const f = g->face;
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const int start_edge = g->start_edge;
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f->used = 1;
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// update the group's bounding box
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for (int i = 0 ; i < 3 ; i++)
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{
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const float px = g->p[i][0];
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const float py = g->p[i][1];
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if (px < poly_min[0]) poly_min[0] = px;
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if (px > poly_max[0]) poly_max[0] = px;
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if (py < poly_min[1]) poly_min[1] = py;
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if (py > poly_max[1]) poly_max[1] = py;
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}
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|
|
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if (debug) fprintf(stderr, "%p: adding to poly\n", f);
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for(int pass = 0 ; pass < 2 ; pass++)
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{
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// for each edge, find the triangle that matches
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for (int i = 0 ; i < 3 ; i++)
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{
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const int edge = (i + start_edge) % 3;
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face_t * const f2 = f->next[edge];
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assert(f2 != NULL);
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if (f2->used)
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continue;
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if (pass == 0 && f->coplanar[edge] == 0)
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continue;
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|
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// create a group that translates and rotates
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// such that it lines up with this edge
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float trans_x, trans_y, rotate;
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if (i == 0)
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{
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trans_x = g->a;
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trans_y = 0;
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rotate = M_PI;
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} else
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if (i == 1)
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{
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trans_x = g->x2;
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trans_y = g->y2;
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rotate = -atan2(g->y2, g->a - g->x2);
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} else
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if (i == 2)
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{
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trans_x = 0;
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trans_y = 0;
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rotate = atan2(g->y2, g->x2);
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} else {
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errx(EXIT_FAILURE, "edge %d invalid?\n", i);
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}
|
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|
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// position this one translated and rotated
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|
poly_t * const g2 = calloc(1, sizeof(*g2));
|
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g2->face = f2;
|
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g2->start_edge = f->next_edge[edge];
|
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|
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poly_position(
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g2,
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g,
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rotate,
|
|
trans_x,
|
|
trans_y
|
|
);
|
|
|
|
if (overlap_check(poly_root, g2))
|
|
{
|
|
free(g2);
|
|
continue;
|
|
}
|
|
|
|
// no overlap, add it to the current group
|
|
g->next[i] = g2;
|
|
g2->next[0] = g;
|
|
f2->used = 1;
|
|
|
|
// if g2 is a coplanar triangle, process it now rather than
|
|
// defering the work.
|
|
if (f->coplanar[edge] == 0)
|
|
enqueue(g, g2, 1);
|
|
else
|
|
enqueue(g, g2, 0);
|
|
}
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
|
|
void
|
|
svg_text(
|
|
float x,
|
|
float y,
|
|
float angle,
|
|
const char * fmt,
|
|
...
|
|
)
|
|
{
|
|
|
|
printf("<g transform=\"translate(%f %f) rotate(%f)\">",
|
|
x,
|
|
y,
|
|
angle
|
|
);
|
|
|
|
printf("<text x=\"-2\" y=\"1.5\" style=\"font-size:1.5px;\">");
|
|
|
|
va_list ap;
|
|
va_start(ap, fmt);
|
|
vprintf(fmt, ap);
|
|
va_end(ap);
|
|
|
|
printf("</text></g>\n");
|
|
}
|
|
|
|
void
|
|
poly_print(
|
|
poly_t * const g
|
|
)
|
|
{
|
|
const face_t * const f = g->face;
|
|
const int start_edge = g->start_edge;
|
|
|
|
g->printed = 1;
|
|
|
|
// draw this triangle;
|
|
// if the edge is an outside, which means that the group
|
|
// has no next element, draw a cut line. If there is an
|
|
// adjacent neighbor and it is not coplanar, draw a score line
|
|
printf("<g><!-- %p %d %f %f->%p %f->%p %f->%p -->\n",
|
|
f,
|
|
g->start_edge, g->rot * 180/M_PI,
|
|
f->sides[0],
|
|
f->next[0],
|
|
f->sides[1],
|
|
f->next[1],
|
|
f->sides[2],
|
|
f->next[2]
|
|
);
|
|
|
|
int cut_lines = 0;
|
|
const uintptr_t a1 = (0x7FFFF & (uintptr_t) f) >> 3;
|
|
|
|
for (int i = 0 ; i < 3 ; i++)
|
|
{
|
|
const int edge = (start_edge + i) % 3;
|
|
poly_t * const next = g->next[i];
|
|
|
|
if (!next)
|
|
{
|
|
// draw a cut line
|
|
const float * const p1 = g->p[i];
|
|
const float * const p2 = g->p[(i+1) % 3];
|
|
const float cx = (p2[0] + p1[0]) / 2;
|
|
const float cy = (p2[1] + p1[1]) / 2;
|
|
const float dx = (p2[0] - p1[0]);
|
|
const float dy = (p2[1] - p1[1]);
|
|
const float angle = atan2(dy, dx) * 180 / M_PI;
|
|
|
|
svg_line("#FF0000", p1, p2, 0);
|
|
cut_lines++;
|
|
|
|
// use the lower address as the label
|
|
if (draw_labels)
|
|
{
|
|
uintptr_t a2 = (0x7FFFF & (uintptr_t) f->next[edge]) >> 3;
|
|
if (a2 > a1)
|
|
a2 = a1;
|
|
svg_text(cx, cy, angle, "%04x", a2);
|
|
}
|
|
|
|
continue;
|
|
}
|
|
|
|
if (next->printed)
|
|
continue;
|
|
|
|
if (f->coplanar[edge] < 0)
|
|
{
|
|
// draw a mountain score line since they are not coplanar
|
|
svg_line("#00FF00", g->p[i], g->p[(i+1) % 3], 1);
|
|
} else
|
|
if (f->coplanar[edge] > 0)
|
|
{
|
|
// draw a valley score line since they are not coplanar
|
|
svg_line("#00FF00", g->p[i], g->p[(i+1) % 3], 0);
|
|
} else {
|
|
// draw a shadow line since they are coplanar
|
|
//svg_line("#F0F0F0", g->p[i], g->p[(i+1) % 3]);
|
|
}
|
|
}
|
|
|
|
/*
|
|
// only draw labels if requested and if there are any cut-edges
|
|
// on this polygon.
|
|
const float tx = (g->p[0][0] + g->p[1][0] + g->p[2][0]) / 3.0;
|
|
const float ty = (g->p[0][1] + g->p[1][1] + g->p[2][1]) / 3.0;
|
|
if (draw_labels && cut_lines > 0)
|
|
svg_text(tx, ty, 0, "%04x",
|
|
(0x7FFFF & (uintptr_t) f) >> 3);
|
|
*/
|
|
|
|
printf("</g>\n");
|
|
|
|
for (int i = 0 ; i < 3 ; i++)
|
|
{
|
|
poly_t * const next = g->next[i];
|
|
if (!next || next->printed)
|
|
continue;
|
|
|
|
poly_print(next);
|
|
}
|
|
}
|
|
|
|
|
|
/* Returns the 0 for coplanar, negative for mountain, positive for valley.
|
|
* (approximates the angle between two triangles that share one edge).
|
|
*/
|
|
int
|
|
coplanar_check(
|
|
const stl_face_t * const f1,
|
|
const stl_face_t * const f2
|
|
)
|
|
{
|
|
// find the four distinct points
|
|
v3_t x1 = f1->p[0];
|
|
v3_t x2 = f1->p[1];
|
|
v3_t x3 = f1->p[2];
|
|
v3_t x4;
|
|
|
|
for (int i = 0 ; i < 3 ; i++)
|
|
{
|
|
x4 = f2->p[i];
|
|
if (v3_eq(&x1, &x4))
|
|
continue;
|
|
if (v3_eq(&x2, &x4))
|
|
continue;
|
|
if (v3_eq(&x3, &x4))
|
|
continue;
|
|
break;
|
|
}
|
|
|
|
// (x3-x1) . ((x2-x1) X (x4-x3)) == 0
|
|
v3_t dx31 = v3_sub(x3, x1);
|
|
v3_t dx21 = v3_sub(x2, x1);
|
|
v3_t dx43 = v3_sub(x4, x3);
|
|
v3_t cross = v3_cross(dx21, dx43);
|
|
float dot = v3_dot(dx31, cross);
|
|
|
|
int check = -EPS < dot && dot < +EPS;
|
|
if (debug) fprintf( stderr, "%p %p %s: %f\n", f1, f2, check ? "yes" : "no", dot);
|
|
return (int) dot;
|
|
}
|
|
|
|
|
|
/** Translate a list of STL triangles into a connected graph of faces.
|
|
*
|
|
* If there are any triangles that do not have three connected edges,
|
|
* the first error will be reported and NULL will be returned.
|
|
*/
|
|
face_t *
|
|
stl2faces(
|
|
const stl_face_t * const stl_faces,
|
|
const int num_triangles
|
|
)
|
|
{
|
|
face_t * const faces = calloc(num_triangles, sizeof(*faces));
|
|
|
|
// convert the stl triangles into faces
|
|
for (int i = 0 ; i < num_triangles ; i++)
|
|
{
|
|
const stl_face_t * const stl = &stl_faces[i];
|
|
face_t * const f = &faces[i];
|
|
|
|
f->sides[0] = v3_len(&stl->p[0], &stl->p[1]);
|
|
f->sides[1] = v3_len(&stl->p[1], &stl->p[2]);
|
|
f->sides[2] = v3_len(&stl->p[2], &stl->p[0]);
|
|
if (debug) fprintf(stderr, "%p %f %f %f\n",
|
|
f, f->sides[0], f->sides[1], f->sides[2]);
|
|
}
|
|
|
|
// look to see if there is a matching point
|
|
// in the faces that we've already built
|
|
for (int i = 0 ; i < num_triangles ; i++)
|
|
{
|
|
const stl_face_t * const stl = &stl_faces[i];
|
|
face_t * const f = &faces[i];
|
|
|
|
for (int j = 0 ; j < num_triangles ; j++)
|
|
{
|
|
if (i == j)
|
|
continue;
|
|
|
|
const stl_face_t * const stl2 = &stl_faces[j];
|
|
face_t * const f2 = &faces[j];
|
|
|
|
for (int edge = 0 ; edge < 3 ; edge++)
|
|
{
|
|
if (f->next[edge])
|
|
continue;
|
|
|
|
for (int edge2 = 0 ; edge2 < 3 ; edge2++)
|
|
{
|
|
if (f2->next[edge2])
|
|
continue;
|
|
|
|
if (!edge_eq2(stl, stl2, edge, edge2))
|
|
continue;
|
|
|
|
f->next[edge] = f2;
|
|
f->next_edge[edge] = edge2;
|
|
f2->next[edge2] = f;
|
|
f2->next_edge[edge2] = edge;
|
|
|
|
f->coplanar[edge] =
|
|
f2->coplanar[edge2] = coplanar_check(stl, stl2);
|
|
}
|
|
}
|
|
}
|
|
|
|
// all three edges should be matched
|
|
if (f->next[0] && f->next[1] && f->next[2])
|
|
continue;
|
|
fprintf(stderr, "%d missing edges?\n", i);
|
|
free(faces);
|
|
return NULL;
|
|
}
|
|
|
|
return faces;
|
|
}
|
|
#endif
|
|
|
|
/*
|
|
s = 1/(2*Area)*(p0y*p2x - p0x*p2y + (p2y - p0y)*px + (p0x - p2x)*py);
|
|
t = 1/(2*Area)*(p0x*p1y - p0y*p1x + (p0y - p1y)*px + (p1x - p0x)*py);
|
|
where Area is the (signed) area of the triangle:
|
|
|
|
Area = 0.5 *(-p1y*p2x + p0y*(-p1x + p2x) + p0x*(p1y - p2y) + p1x*p2y);
|
|
Just evaluate s, t and 1-s-t. The point p is inside the triangle if and only if they are all positive.
|
|
*/
|
|
int
|
|
tri_inside(
|
|
const tri_t * const t,
|
|
const v3_t * const p
|
|
)
|
|
{
|
|
const float p0x = t->p[0].p[0];
|
|
const float p0y = t->p[0].p[1];
|
|
const float p1x = t->p[1].p[0];
|
|
const float p1y = t->p[1].p[1];
|
|
const float p2x = t->p[2].p[0];
|
|
const float p2y = t->p[2].p[1];
|
|
|
|
const float px = p->p[0];
|
|
const float py = p->p[1];
|
|
|
|
const float u = p0y*p2x - p0x*p2y + (p2y - p0y)*px + (p0x - p2x)*py;
|
|
const float v = p0x*p1y - p0y*p1x + (p0y - p1y)*px + (p1x - p0x)*py;
|
|
|
|
if (u <= 0 || v <= 0)
|
|
return 0;
|
|
|
|
// maybe inside; check for sure
|
|
if (u + v >= 2 * t->area)
|
|
return 0;
|
|
|
|
// inside!
|
|
if(0) fprintf(stderr, "%p: %f,%f inside %f,%f %f,%f %f,%f\n",
|
|
t,
|
|
px, py,
|
|
p0x, p0y,
|
|
p1x, p1y,
|
|
p2x, p2y
|
|
);
|
|
|
|
return 1;
|
|
}
|
|
|
|
|
|
tri_t *
|
|
tri_new(
|
|
const v3_t * p
|
|
)
|
|
{
|
|
tri_t * const t = calloc(1, sizeof(*t));
|
|
if (!t)
|
|
return NULL;
|
|
for(int i = 0 ; i < 3 ; i++)
|
|
t->p[i] = p[i];
|
|
|
|
// precompute the area
|
|
const float p0x = t->p[0].p[0];
|
|
const float p0y = t->p[0].p[1];
|
|
const float p1x = t->p[1].p[0];
|
|
const float p1y = t->p[1].p[1];
|
|
const float p2x = t->p[2].p[0];
|
|
const float p2y = t->p[2].p[1];
|
|
|
|
t->area = 0.5 *(-p1y*p2x + p0y*(-p1x + p2x) + p0x*(p1y - p2y) + p1x*p2y);
|
|
|
|
// precompute the normal
|
|
t->normal = v3_cross(
|
|
v3_sub(t->p[1], t->p[0]),
|
|
v3_sub(t->p[2], t->p[1])
|
|
);
|
|
|
|
|
|
// compute the bounding box for the triangle
|
|
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
|
|
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;
|
|
*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);
|
|
}
|
|
|
|
|
|
int
|
|
tri_occluded(
|
|
const tri_t * zlist,
|
|
const tri_t * t
|
|
)
|
|
{
|
|
for( const tri_t * t2 = zlist ; t2 ; t2 = t2->next )
|
|
{
|
|
if (t2 == t)
|
|
continue;
|
|
|
|
// if any of the points of t are outside of t2,
|
|
// then t2 does not totally occlude t
|
|
if (!tri_inside(t2, &t->p[0]))
|
|
continue;
|
|
if (!tri_inside(t2, &t->p[1]))
|
|
continue;
|
|
if (!tri_inside(t2, &t->p[2]))
|
|
continue;
|
|
|
|
// if any point of t2 is behind t, then it does not occlude
|
|
// (might intersect, but we don't handle that)
|
|
if (t2->min[2] > t->min[2])
|
|
continue;
|
|
|
|
// looks like we might be occluded
|
|
return 1;
|
|
}
|
|
|
|
// probably not occluded
|
|
return 0;
|
|
}
|
|
|
|
|
|
seg_t *
|
|
seg_new(
|
|
const v3_t p0,
|
|
const v3_t p1
|
|
)
|
|
{
|
|
seg_t * const s = calloc(1, sizeof(*s));
|
|
if (!s)
|
|
return NULL;
|
|
s->p[0] = p0;
|
|
s->p[1] = p1;
|
|
s->next = NULL;
|
|
|
|
return s;
|
|
}
|
|
|
|
|
|
void
|
|
seg_print(
|
|
const seg_t * const s
|
|
)
|
|
{
|
|
fprintf(stderr, "%.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]
|
|
);
|
|
}
|
|
|
|
void
|
|
tri_print(
|
|
const tri_t * const t
|
|
)
|
|
{
|
|
fprintf(stderr, "%.0f,%.0f,%.0f %.0f,%.0f,%.0f %.0f,%.0f,%.0f\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]
|
|
);
|
|
}
|
|
|
|
/** Find the Z point of a given xy point along the segment from p0 to p1.
|
|
*
|
|
* Returns -1 if there is no known Z point.
|
|
*/
|
|
float
|
|
find_z(
|
|
const v3_t * const p0,
|
|
const v3_t * const p1,
|
|
const float x,
|
|
const float y
|
|
)
|
|
{
|
|
const float dx = p1->p[0] - p0->p[0];
|
|
const float dy = p1->p[1] - p0->p[1];
|
|
const float dz = p1->p[2] - p0->p[2];
|
|
|
|
// find the z value of the intersection point
|
|
// on the segment. we don't care about the triangle
|
|
float ratio = 0;
|
|
if (dx != 0)
|
|
{
|
|
ratio = (x - p0->p[0]) / dx;
|
|
} else
|
|
if (dy != 0)
|
|
{
|
|
ratio = (y - p0->p[1]) / dy;
|
|
} else {
|
|
fprintf(stderr, "uh, dx and dy both zero?\n");
|
|
return -1;
|
|
}
|
|
|
|
return p0->p[2] + dz * ratio;
|
|
}
|
|
|
|
|
|
|
|
/*
|
|
int
|
|
tri_line_intersect(
|
|
const tri_t * zlist,
|
|
const tri_t * t
|
|
)
|
|
{
|
|
for( const tri_t * t2 = zlist ; t2 ; t2 = t2->next )
|
|
{
|
|
if (t2 == t)
|
|
continue;
|
|
for(int j = 0 ; j < 3 ; j++)
|
|
{
|
|
const v3_t * const p0 = &t->p[j].p;
|
|
const v3_t * const p1 = &t->p[(j+1) % 3].p;
|
|
*/
|
|
|
|
|
|
/*
|
|
* Recursive algorithm:
|
|
* Given a line segment and a list of triangles,
|
|
* find if the line segment crosses any triangle.
|
|
* If it crosses a triangle the segment will be shortened
|
|
* and an additional one might be created.
|
|
* Recusively try intersecting the new segment (starting at the same triangle)
|
|
* and then continue trying the shortened segment.
|
|
*/
|
|
|
|
void
|
|
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);
|
|
|
|
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, 0.1)
|
|
&& v2_eq(s->src[1].p, t->p[1].p, 0.1))
|
|
continue;
|
|
if (v2_eq(s->src[0].p, t->p[1].p, 0.1)
|
|
&& v2_eq(s->src[1].p, t->p[2].p, 0.1))
|
|
continue;
|
|
if (v2_eq(s->src[0].p, t->p[2].p, 0.1)
|
|
&& v2_eq(s->src[1].p, t->p[0].p, 0.1))
|
|
continue;
|
|
if (v2_eq(s->src[0].p, t->p[1].p, 0.1)
|
|
&& v2_eq(s->src[1].p, t->p[0].p, 0.1))
|
|
continue;
|
|
if (v2_eq(s->src[0].p, t->p[2].p, 0.1)
|
|
&& v2_eq(s->src[1].p, t->p[1].p, 0.1))
|
|
continue;
|
|
if (v2_eq(s->src[0].p, t->p[0].p, 0.1)
|
|
&& v2_eq(s->src[1].p, t->p[2].p, 0.1))
|
|
continue;
|
|
// do a quick test of does this segment even comes
|
|
// close to this triangle
|
|
if (p0x < t->min[0] && p1x < t->min[0]
|
|
&& p0y < t->min[1] && p1y < t->min[1])
|
|
continue;
|
|
if (p0x > t->max[0] && p1x > t->max[0]
|
|
&& p0y > t->max[2] && p1y > t->max[2])
|
|
continue;
|
|
if (p0x < t->min[0] && p1x < t->min[0]
|
|
&& p0y > t->max[2] && p1y > t->max[2])
|
|
continue;
|
|
if (p0x > t->max[0] && p1x > t->max[0]
|
|
&& p0y < t->min[1] && p1y < t->min[1])
|
|
continue;
|
|
|
|
// make sure this isn't the same actual line
|
|
if (v3_eq(&s->src[0], &t->p[0]) || v3_eq(&s->src[1], &t->p[1]))
|
|
continue;
|
|
if (v3_eq(&s->src[0], &t->p[1]) || v3_eq(&s->src[1], &t->p[2]))
|
|
continue;
|
|
if (v3_eq(&s->src[0], &t->p[2]) || v3_eq(&s->src[1], &t->p[0]))
|
|
continue;
|
|
#endif
|
|
|
|
int inside0 = tri_inside(t, &s->p[0]);
|
|
int inside1 = tri_inside(t, &s->p[1]);
|
|
|
|
// if both are inside we discard this segment
|
|
if (inside0 && inside1)
|
|
{
|
|
//svg_line("#0000FF", s->p[0].p, s->p[1].p, 0);
|
|
//svg_line("#00FF00", t->p[0].p, t->p[1].p, 0);
|
|
//svg_line("#00FF00", t->p[1].p, t->p[2].p, 0);
|
|
//svg_line("#00FF00", t->p[2].p, t->p[0].p, 0);
|
|
fprintf(stderr, "BOTH INSIDE\n");
|
|
tri_print(t);
|
|
seg_print(s);
|
|
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;
|
|
|
|
// deal with corner cases where the segment
|
|
// exactly lines up with the triangle edge
|
|
// we do not treat this as an intersection
|
|
if (-EPS < ratio && ratio < EPS)
|
|
{
|
|
inside0 = 0;
|
|
} else
|
|
if (1-EPS < ratio && ratio < 1+EPS)
|
|
{
|
|
inside1 = 0;
|
|
} else {
|
|
// this is a real intersection
|
|
intersections++;
|
|
}
|
|
}
|
|
|
|
// if none of them intersect, we keep looking
|
|
if (intersections == 0)
|
|
continue;
|
|
|
|
fprintf(stderr, "split %d %d inter %d\n", inside0 , inside1, intersections);
|
|
if (intersections == 3)
|
|
{
|
|
fprintf(stderr, "uh, three intersections?\n");
|
|
return;
|
|
}
|
|
|
|
if (intersections == 2)
|
|
{
|
|
if (inside0 || inside1)
|
|
{
|
|
fprintf(stderr, "uh, inside but two intersections?\n");
|
|
//return;
|
|
}
|
|
|
|
// if the segment intersection is closer than the triangle,
|
|
// then we do nothing. degenerate cases are not handled
|
|
if (is[0].p[2] <= it[0].p[2]
|
|
|| is[1].p[2] <= it[1].p[2])
|
|
{
|
|
fprintf(stderr, "ignoring collision since z %f < %f || %f < %f\n",
|
|
is[0].p[2], it[0].p[2],
|
|
is[1].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
|
|
|
|
|
|
const float d0 = v3_len(&s->p[0], &is[0]);
|
|
const float d1 = v3_len(&s->p[0], &is[1]);
|
|
fprintf(stderr, "two intersections %.0f %.0f\n", d0, d1);
|
|
seg_t * news;
|
|
if (d0 < d1)
|
|
{
|
|
// split from p0 to ix0
|
|
news = seg_new(s->p[0], is[0]);
|
|
s->p[0] = is[1];
|
|
} else {
|
|
// split from p0 to ix1
|
|
news = seg_new(s->p[0], is[1]);
|
|
s->p[0] = is[0];
|
|
}
|
|
fprintf(stderr, "old segment:" );
|
|
seg_print(s);
|
|
fprintf(stderr, "new segment:" );
|
|
seg_print(news);
|
|
|
|
// recursively start splitting the new segment
|
|
// starting at our current z-depth
|
|
tri_seg_intersect(zlist, news, slist_visible);
|
|
|
|
// continue splitting our current segment
|
|
continue;
|
|
}
|
|
|
|
if (intersections == 1)
|
|
{
|
|
// if there is an intersection, but the segment intercept
|
|
// is close 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])
|
|
continue;
|
|
|
|
// segment is behind the triangle, so it needs to be
|
|
// cut into pieces
|
|
if (inside0)
|
|
{
|
|
// shorten it on the 0 side
|
|
s->p[0] = is[0];
|
|
continue;
|
|
} else
|
|
if (inside1)
|
|
{
|
|
// shorten it on the 1 side
|
|
s->p[1] = is[0];
|
|
continue;
|
|
} else
|
|
if (v2_eq(s->p[0].p, is[0].p, 0.1))
|
|
{
|
|
// the 0 side is on the triangle, don't bother
|
|
continue;
|
|
} else
|
|
if (v2_eq(s->p[1].p, is[0].p, 0.1))
|
|
{
|
|
// the 1 side is on the triangle, don't bother
|
|
continue;
|
|
} else {
|
|
fprintf(stderr, "uh, both outside but one intersection? %.3f,%.3f\n",
|
|
is[0].p[0],
|
|
is[0].p[1]
|
|
);
|
|
seg_print(s);
|
|
tri_print(t);
|
|
//svg_line("#00FF00", s->p[0].p, s->p[1].p, 0);
|
|
continue;
|
|
}
|
|
}
|
|
}
|
|
|
|
// if we've reached here the segment is visible
|
|
// and should be added to the visible list
|
|
if(0) fprintf(stderr, "good: %.0f,%.0f,%.0f-> %.0f,%.0f,%.0f\n",
|
|
s->p[0].p[0],
|
|
s->p[0].p[1],
|
|
s->p[0].p[2],
|
|
s->p[1].p[0],
|
|
s->p[1].p[1],
|
|
s->p[1].p[2]
|
|
);
|
|
|
|
s->next = *slist_visible;
|
|
*slist_visible = s;
|
|
}
|
|
|
|
|
|
|
|
int main(
|
|
int argc,
|
|
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);
|
|
|
|
float phi = argc > 1 ? atof(argv[1]) * M_PI/180 : 0;
|
|
float theta = argc > 2 ? atof(argv[2]) * M_PI/180 : 0;
|
|
float psi = argc > 3 ? atof(argv[3]) * M_PI/180 : 0;
|
|
|
|
ssize_t rc = read(0, buf, max_len);
|
|
if (rc == -1)
|
|
return EXIT_FAILURE;
|
|
|
|
const stl_header_t * const hdr = (const void*) buf;
|
|
const stl_face_t * const stl_faces = (const void*)(hdr+1);
|
|
const int num_triangles = hdr->num_triangles;
|
|
|
|
if(debug)
|
|
{
|
|
fprintf(stderr, "header: '%s'\n", hdr->header);
|
|
fprintf(stderr, "num: %d\n", num_triangles);
|
|
}
|
|
|
|
|
|
// looking at (0,0,0)
|
|
v3_t eye = { { 0, 0, 400 } };
|
|
const camera_t * const cam = camera_new(eye, phi, theta, psi);
|
|
|
|
printf("<svg xmlns=\"http://www.w3.org/2000/svg\">\n");
|
|
|
|
float off_x = 500;
|
|
float off_y = 500;
|
|
printf("<g transform=\"translate(%f %f)\">\n", off_x, off_y);
|
|
|
|
int rejected = 0;
|
|
tri_t * zlist = NULL;
|
|
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++)
|
|
{
|
|
const stl_face_t * const stl = &stl_faces[i];
|
|
|
|
v3_t s[3];
|
|
|
|
for(int j = 0 ; j < 3 ; j++)
|
|
camera_project(cam, &stl->p[j], &s[j]);
|
|
|
|
tri_t * const tri = tri_new(s);
|
|
|
|
// reject this face if any of the vertices are behind us
|
|
if (tri->min[2] < 0)
|
|
goto reject;
|
|
|
|
// do a back-face cull to determine if this triangle
|
|
// is not facing us. we have to determine the orientation
|
|
// from the winding of the new projection
|
|
if (tri->normal.p[2] <= 0)
|
|
goto reject;
|
|
|
|
// it passes the first tests, so insert the triangle
|
|
// into the list and the three line segments
|
|
tri_insert(&zlist, tri);
|
|
|
|
for(int j = 0 ; j < 3 ; j++)
|
|
{
|
|
seg_t * s = seg_new(tri->p[j], tri->p[(j+1) % 3]);
|
|
s->next = slist;
|
|
slist = s;
|
|
}
|
|
|
|
retained++;
|
|
if( retained > 3)
|
|
break;
|
|
|
|
continue;
|
|
|
|
reject:
|
|
tri_delete(tri);
|
|
rejected++;
|
|
}
|
|
|
|
if (debug)
|
|
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;
|
|
|
|
if(1)
|
|
{
|
|
// 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);
|
|
|
|
}
|
|
} else {
|
|
// don't do any intersection tests
|
|
slist_visible = slist;
|
|
slist = NULL;
|
|
}
|
|
|
|
// display all of the visible segments
|
|
for(seg_t * s = slist_visible ; s ; s = s->next)
|
|
{
|
|
svg_line("#FF0000", s->p[0].p, s->p[1].p, 0);
|
|
}
|
|
|
|
if (debug)
|
|
fprintf(stderr, "Occluded %d triangles\n", rejected);
|
|
|
|
|
|
printf("</g>\n");
|
|
printf("</svg>\n");
|
|
|
|
return 0;
|
|
}
|