70 lines
1.7 KiB
C
70 lines
1.7 KiB
C
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#include <sys/stat.h> /* struct stat */
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#include <stdlib.h> /* malloc() */
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#include <stdio.h> /* fprintf() */
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#include <math.h> /* sqrt() */
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#include "stl.h"
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/* load a STL file and return a pointer to the stl_t struct */
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stl_t * stl_load(const char * filename)
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{
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struct stat s;
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if (stat(filename, &s))
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{
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fprintf(stderr, "Couldn't stat '%s'\n", filename);
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return NULL;
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}
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if (s.st_size < sizeof(stl_t))
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{
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fprintf(stderr, "Size of '%s' only %d bytes!\n", filename, s.st_size);
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return NULL;
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}
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FILE *fil;
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if ((fil = fopen(filename, "rb")) == NULL)
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{
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fprintf(stderr, "Couldn't open '%s'\n", filename);
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return NULL;
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}
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stl_t * stl = (stl_t *) malloc(s.st_size);
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fread(stl, 1, s.st_size, fil);
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fclose(fil);
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if (s.st_size <
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sizeof(stl_t) + sizeof(stl_face_t) * (stl_num_faces(stl)-1))
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{
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fprintf(stderr, "Size of '%s' only %d bytes, but has %d faces!\n",
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filename, s.st_size, stl_num_faces(stl));
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free(stl);
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return NULL;
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}
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return stl;
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}
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/* fill vector pointed to by normal with the normal of the face */
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void stl_get_face_normal(stl_t * stl, int face, float * normal)
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{
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float e1[3];
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float e2[3];
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int i;
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for (i = 0; i < 3; i++)
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{
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e1[i] = stl_face(stl, face).vertices[1][i] -
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stl_face(stl, face).vertices[0][i];
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e2[i] = stl_face(stl, face).vertices[2][i] -
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stl_face(stl, face).vertices[1][i];
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}
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/* take the cross product of the first two edges */
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normal[0] = e1[1] * e2[2] - e1[2] * e2[1];
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normal[1] = e1[2] * e2[0] - e1[0] * e2[2];
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normal[2] = e1[0] * e2[1] - e1[1] * e2[0];
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/* then normalize */
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double l;
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l = sqrt(normal[0] * normal[0] +
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normal[1] * normal[1] +
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normal[2] * normal[2]);
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normal[0] /= l;
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normal[1] /= l;
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normal[2] /= l;
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}
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