127 lines
2.3 KiB
C
127 lines
2.3 KiB
C
#include <stdio.h>
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#include <stdlib.h>
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#include <stdint.h>
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#include <unistd.h>
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#define EPS 0.0001
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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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float p[3];
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} v3_t;
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typedef struct
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{
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v3_t normal;
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v3_t p0;
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v3_t p1;
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v3_t p2;
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} __attribute__((__packed__))
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stl_face_t;
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#define MAX_POINTS 24
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typedef struct
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{
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int n;
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int p[MAX_POINTS];
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} poly_t;
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static int
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v3_eq(
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const v3_t * v1,
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const v3_t * v2
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)
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{
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float dx = v1->p[0] - v2->p[0];
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float dy = v1->p[1] - v2->p[1];
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float dz = v1->p[2] - v2->p[2];
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if (-EPS < dx && dx < EPS
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&& -EPS < dy && dy < EPS
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&& -EPS < dz && dz < EPS)
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return 1;
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return 0;
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}
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int main(void)
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{
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const size_t max_len = 1 << 20;
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uint8_t * const buf = calloc(max_len, 1);
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ssize_t rc = read(0, buf, max_len);
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if (rc == -1)
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return EXIT_FAILURE;
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const stl_header_t * const hdr = (const void*) buf;
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const stl_face_t * const faces = (const void*)(hdr+1);
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const int num_triangles = hdr->num_triangles;
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fprintf(stderr, "header: '%s'\n", hdr->header);
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fprintf(stderr, "num: %d\n", num_triangles);
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// worst case -- all separate polygons
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poly_t * const polys = calloc(num_triangles, sizeof(*polys));
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// Collapse coplanar triangles into larger polygons
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v3_t * const vertices = calloc(num_triangles, 3);
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int num_vertices = 0;
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for(int i = 0 ; i < num_triangles ; i++)
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{
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// see if this matches an existing vertex
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const stl_face_t * const t = &faces[i];
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poly_t * const p = &polys[i];
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p->n = 3;
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p->p[0] = p->p[1] = p->p[2] = -1;
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for (int j = 0 ; j < num_vertices ; j++)
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{
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const v3_t * const v = &vertices[j];
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if (p->p[0] == -1 && v3_eq(v, &t->p0))
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p->p[1] = j;
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if (p->p[1] == -1 && v3_eq(v, &t->p1))
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p->p[1] = j;
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if (p->p[2] == -1 && v3_eq(v, &t->p2))
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p->p[2] = j;
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// check if we've found all of them
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if (p->p[0] >= 0 && p->p[1] >= 0 && p->p[2] >= 0)
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break;
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}
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// create new points if we haven't found matches
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if (p->p[0] < 0)
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{
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p->p[0] = num_vertices;
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vertices[num_vertices++] = t->p0;
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}
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if (p->p[1] < 0)
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{
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p->p[1] = num_vertices;
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vertices[num_vertices++] = t->p1;
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}
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if (p->p[3] < 0)
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{
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p->p[3] = num_vertices;
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vertices[num_vertices++] = t->p2;
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}
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}
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fprintf(stderr, "unique vertices: %d\n", num_vertices);
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return 0;
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}
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