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stl: computing normals in the stl module by cross product now

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git-svn-id: svn://anubis/misc/stl@7 bd8a9e45-a331-0410-811e-c64571078777
This commit is contained in:
josh 2007-06-03 03:23:32 +00:00
parent 2b94b8b523
commit 47911edec3
3 changed files with 40 additions and 2 deletions
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11
stl-viewer.c
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@ -101,13 +101,14 @@ GLuint buildDL(void)
unsigned int i;
int dfltClrAct = 1;
GLfloat color[4];
float normal[3];
color[3] = 0.0f;
GLuint dl = glGenLists(1);
glNewList(dl, GL_COMPILE);
glBegin(GL_TRIANGLES);
glMaterialfv(GL_FRONT, GL_AMBIENT_AND_DIFFUSE, default_color);
for (i = 0; i < n_faces; i++)
{
#if 0
if (stl_attr_color_valid(stl_face(stl, i).attribute))
{
color[0] = stl_attr_color_r(stl_face(stl, i).attribute) / (float) 255;
@ -119,7 +120,13 @@ GLuint buildDL(void)
else if (!dfltClrAct)
glMaterialfv(GL_FRONT, GL_AMBIENT_AND_DIFFUSE,
default_color);
glNormal3fv(stl_face(stl, i).normal);
#endif
stl_get_face_normal(stl, i, normal);
printf("normal: %f, %f, %f\n",
normal[0],
normal[1],
normal[2]);
glNormal3fv(normal);
int j;
for (j = 0; j < 3; j++)
glVertex3fv(stl_face(stl, i).vertices[j]);

30
stl.c
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@ -2,6 +2,7 @@
#include <sys/stat.h> /* struct stat */
#include <stdlib.h> /* malloc() */
#include <stdio.h> /* fprintf() */
#include <math.h> /* sqrt() */
#include "stl.h"
/* load a STL file and return a pointer to the stl_t struct */
@ -37,3 +38,32 @@ stl_t * stl_load(const char * filename)
}
return stl;
}
/* fill vector pointed to by normal with the normal of the face */
void stl_get_face_normal(stl_t * stl, int face, float * normal)
{
float e1[3];
float e2[3];
int i;
for (i = 0; i < 3; i++)
{
e1[i] = stl_face(stl, face).vertices[1][i] -
stl_face(stl, face).vertices[0][i];
e2[i] = stl_face(stl, face).vertices[2][i] -
stl_face(stl, face).vertices[1][i];
}
/* take the cross product of the first two edges */
normal[0] = e1[1] * e2[2] - e1[2] * e2[1];
normal[1] = e1[2] * e2[0] - e1[0] * e2[2];
normal[2] = e1[0] * e2[1] - e1[1] * e2[0];
/* then normalize */
double l;
l = sqrt(normal[0] * normal[0] +
normal[1] * normal[1] +
normal[2] * normal[2]);
normal[0] /= l;
normal[1] /= l;
normal[2] /= l;
}

1
stl.h
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@ -37,6 +37,7 @@ typedef struct stl_s
/* functions */
stl_t * stl_load(const char * filename);
void stl_get_face_normal(stl_t * stl, int face, float * normal);
#ifdef __cplusplus