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glm.cpp
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/*
glm.c
Nate Robins, 1997
[email protected], http://www.pobox.com/~ndr/
Wavefront OBJ model file format reader/writer/manipulator.
Includes routines for generating smooth normals with
preservation of edges, welding redundant vertices & texture
coordinate generation (spheremap and planar projections) + more.
*/
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include "glm.h"
#define T(x) (model->triangles[(x)])
/* _GLMnode: general purpose node
*/
typedef struct _GLMnode {
GLuint index;
GLboolean averaged;
struct _GLMnode* next;
} GLMnode;
/* glmMax: returns the maximum of two floats */
static GLfloat
glmMax(GLfloat a, GLfloat b)
{
if (b > a)
return b;
return a;
}
/* glmAbs: returns the absolute value of a float */
static GLfloat
glmAbs(GLfloat f)
{
if (f < 0)
return -f;
return f;
}
/* glmDot: compute the dot product of two vectors
*
* u - array of 3 GLfloats (GLfloat u[3])
* v - array of 3 GLfloats (GLfloat v[3])
*/
static GLfloat
glmDot(GLfloat* u, GLfloat* v)
{
assert(u); assert(v);
return u[0]*v[0] + u[1]*v[1] + u[2]*v[2];
}
/* glmCross: compute the cross product of two vectors
*
* u - array of 3 GLfloats (GLfloat u[3])
* v - array of 3 GLfloats (GLfloat v[3])
* n - array of 3 GLfloats (GLfloat n[3]) to return the cross product in
*/
static GLvoid
glmCross(GLfloat* u, GLfloat* v, GLfloat* n)
{
assert(u); assert(v); assert(n);
n[0] = u[1]*v[2] - u[2]*v[1];
n[1] = u[2]*v[0] - u[0]*v[2];
n[2] = u[0]*v[1] - u[1]*v[0];
}
/* glmNormalize: normalize a vector
*
* v - array of 3 GLfloats (GLfloat v[3]) to be normalized
*/
static GLvoid
glmNormalize(GLfloat* v)
{
GLfloat l;
assert(v);
l = (GLfloat)sqrt(v[0]*v[0] + v[1]*v[1] + v[2]*v[2]);
v[0] /= l;
v[1] /= l;
v[2] /= l;
}
/* glmEqual: compares two vectors and returns GL_TRUE if they are
* equal (within a certain threshold) or GL_FALSE if not. An epsilon
* that works fairly well is 0.000001.
*
* u - array of 3 GLfloats (GLfloat u[3])
* v - array of 3 GLfloats (GLfloat v[3])
*/
static GLboolean
glmEqual(GLfloat* u, GLfloat* v, GLfloat epsilon)
{
if (glmAbs(u[0] - v[0]) < epsilon &&
glmAbs(u[1] - v[1]) < epsilon &&
glmAbs(u[2] - v[2]) < epsilon)
{
return GL_TRUE;
}
return GL_FALSE;
}
/* glmWeldVectors: eliminate (weld) vectors that are within an
* epsilon of each other.
*
* vectors - array of GLfloat[3]'s to be welded
* numvectors - number of GLfloat[3]'s in vectors
* epsilon - maximum difference between vectors
*
*/
GLfloat*
glmWeldVectors(GLfloat* vectors, GLuint* numvectors, GLfloat epsilon)
{
GLfloat* copies;
GLuint copied;
GLuint i, j;
copies = (GLfloat*)malloc(sizeof(GLfloat) * 3 * (*numvectors + 1));
memcpy(copies, vectors, (sizeof(GLfloat) * 3 * (*numvectors + 1)));
copied = 1;
for (i = 1; i <= *numvectors; i++) {
for (j = 1; j <= copied; j++) {
if (glmEqual(&vectors[3 * i], &copies[3 * j], epsilon)) {
goto duplicate;
}
}
/* must not be any duplicates -- add to the copies array */
copies[3 * copied + 0] = vectors[3 * i + 0];
copies[3 * copied + 1] = vectors[3 * i + 1];
copies[3 * copied + 2] = vectors[3 * i + 2];
j = copied; /* pass this along for below */
copied++;
duplicate:
/* set the first component of this vector to point at the correct
index into the new copies array */
vectors[3 * i + 0] = (GLfloat)j;
}
*numvectors = copied-1;
return copies;
}
/* glmFindGroup: Find a group in the model
*/
GLMgroup*
glmFindGroup(GLMmodel* model, char* name)
{
GLMgroup* group;
assert(model);
group = model->groups;
while(group) {
if (!strcmp(name, group->name))
break;
group = group->next;
}
return group;
}
/* glmAddGroup: Add a group to the model
*/
GLMgroup*
glmAddGroup(GLMmodel* model, char* name)
{
GLMgroup* group;
group = glmFindGroup(model, name);
if (!group) {
group = (GLMgroup*)malloc(sizeof(GLMgroup));
group->name = strdup(name);
group->material = 0;
group->numtriangles = 0;
group->triangles = NULL;
group->next = model->groups;
model->groups = group;
model->numgroups++;
}
return group;
}
/* glmFindGroup: Find a material in the model
*/
GLuint
glmFindMaterial(GLMmodel* model, char* name)
{
GLuint i;
/* XXX doing a linear search on a string key'd list is pretty lame,
but it works and is fast enough for now. */
for (i = 0; i < model->nummaterials; i++) {
if (!strcmp(model->materials[i].name, name))
goto found;
}
/* didn't find the name, so print a warning and return the default
material (0). */
printf("glmFindMaterial(): can't find material \"%s\".\n", name);
i = 0;
found:
return i;
}
/* glmDirName: return the directory given a path
*
* path - filesystem path
*
* NOTE: the return value should be free'd.
*/
static char*
glmDirName(char* path)
{
char* dir;
char* s;
dir = strdup(path);
s = strrchr(dir, '/');
if (s)
s[1] = '\0';
else
dir[0] = '\0';
return dir;
}
/* glmReadMTL: read a wavefront material library file
*
* model - properly initialized GLMmodel structure
* name - name of the material library
*/
static GLvoid
glmReadMTL(GLMmodel* model, char* name)
{
FILE* file;
char* dir;
char* filename;
char buf[128];
GLuint nummaterials, i;
dir = glmDirName(model->pathname);
filename = (char*)malloc(sizeof(char) * (strlen(dir) + strlen(name) + 1));
strcpy(filename, dir);
strcat(filename, name);
free(dir);
file = fopen(filename, "r");
if (!file) {
fprintf(stderr, "glmReadMTL() failed: can't open material file \"%s\".\n",
filename);
exit(1);
}
free(filename);
/* count the number of materials in the file */
nummaterials = 1;
while(fscanf(file, "%s", buf) != EOF) {
switch(buf[0]) {
case '#': /* comment */
/* eat up rest of line */
fgets(buf, sizeof(buf), file);
break;
case 'n': /* newmtl */
fgets(buf, sizeof(buf), file);
nummaterials++;
sscanf(buf, "%s %s", buf, buf);
break;
default:
/* eat up rest of line */
fgets(buf, sizeof(buf), file);
break;
}
}
rewind(file);
model->materials = (GLMmaterial*)malloc(sizeof(GLMmaterial) * nummaterials);
model->nummaterials = nummaterials;
/* set the default material */
for (i = 0; i < nummaterials; i++) {
model->materials[i].name = NULL;
model->materials[i].shininess = 65.0;
model->materials[i].diffuse[0] = 0.8;
model->materials[i].diffuse[1] = 0.8;
model->materials[i].diffuse[2] = 0.8;
model->materials[i].diffuse[3] = 1.0;
model->materials[i].ambient[0] = 0.2;
model->materials[i].ambient[1] = 0.2;
model->materials[i].ambient[2] = 0.2;
model->materials[i].ambient[3] = 1.0;
model->materials[i].specular[0] = 0.0;
model->materials[i].specular[1] = 0.0;
model->materials[i].specular[2] = 0.0;
model->materials[i].specular[3] = 1.0;
}
model->materials[0].name = strdup("default");
/* now, read in the data */
nummaterials = 0;
while(fscanf(file, "%s", buf) != EOF) {
switch(buf[0]) {
case '#': /* comment */
/* eat up rest of line */
fgets(buf, sizeof(buf), file);
break;
case 'n': /* newmtl */
fgets(buf, sizeof(buf), file);
sscanf(buf, "%s %s", buf, buf);
nummaterials++;
model->materials[nummaterials].name = strdup(buf);
break;
case 'N':
fscanf(file, "%f", &model->materials[nummaterials].shininess);
/* wavefront shininess is from [0, 1000], so scale for OpenGL */
model->materials[nummaterials].shininess /= 1000.0;
model->materials[nummaterials].shininess *= 128.0;
break;
case 'K':
switch(buf[1]) {
case 'd':
fscanf(file, "%f %f %f",
&model->materials[nummaterials].diffuse[0],
&model->materials[nummaterials].diffuse[1],
&model->materials[nummaterials].diffuse[2]);
break;
case 's':
fscanf(file, "%f %f %f",
&model->materials[nummaterials].specular[0],
&model->materials[nummaterials].specular[1],
&model->materials[nummaterials].specular[2]);
break;
case 'a':
fscanf(file, "%f %f %f",
&model->materials[nummaterials].ambient[0],
&model->materials[nummaterials].ambient[1],
&model->materials[nummaterials].ambient[2]);
break;
default:
/* eat up rest of line */
fgets(buf, sizeof(buf), file);
break;
}
break;
default:
/* eat up rest of line */
fgets(buf, sizeof(buf), file);
break;
}
}
}
/* glmWriteMTL: write a wavefront material library file
*
* model - properly initialized GLMmodel structure
* modelpath - pathname of the model being written
* mtllibname - name of the material library to be written
*/
static GLvoid
glmWriteMTL(GLMmodel* model, char* modelpath, char* mtllibname)
{
FILE* file;
char* dir;
char* filename;
GLMmaterial* material;
GLuint i;
dir = glmDirName(modelpath);
filename = (char*)malloc(sizeof(char) * (strlen(dir)+strlen(mtllibname)));
strcpy(filename, dir);
strcat(filename, mtllibname);
free(dir);
/* open the file */
file = fopen(filename, "w");
if (!file) {
fprintf(stderr, "glmWriteMTL() failed: can't open file \"%s\".\n",
filename);
exit(1);
}
free(filename);
/* spit out a header */
fprintf(file, "# \n");
fprintf(file, "# Wavefront MTL generated by GLM library\n");
fprintf(file, "# \n");
fprintf(file, "# GLM library\n");
fprintf(file, "# Nate Robins\n");
fprintf(file, "# [email protected]\n");
fprintf(file, "# http://www.pobox.com/~ndr\n");
fprintf(file, "# \n\n");
for (i = 0; i < model->nummaterials; i++) {
material = &model->materials[i];
fprintf(file, "newmtl %s\n", material->name);
fprintf(file, "Ka %f %f %f\n",
material->ambient[0], material->ambient[1], material->ambient[2]);
fprintf(file, "Kd %f %f %f\n",
material->diffuse[0], material->diffuse[1], material->diffuse[2]);
fprintf(file, "Ks %f %f %f\n",
material->specular[0],material->specular[1],material->specular[2]);
fprintf(file, "Ns %f\n", material->shininess / 128.0 * 1000.0);
fprintf(file, "\n");
}
}
/* glmFirstPass: first pass at a Wavefront OBJ file that gets all the
* statistics of the model (such as #vertices, #normals, etc)
*
* model - properly initialized GLMmodel structure
* file - (fopen'd) file descriptor
*/
static GLvoid
glmFirstPass(GLMmodel* model, FILE* file)
{
GLuint numvertices; /* number of vertices in model */
GLuint numnormals; /* number of normals in model */
GLuint numtexcoords; /* number of texcoords in model */
GLuint numtriangles; /* number of triangles in model */
GLMgroup* group; /* current group */
unsigned v, n, t;
char buf[128];
/* make a default group */
group = glmAddGroup(model, "default");
numvertices = numnormals = numtexcoords = numtriangles = 0;
while(fscanf(file, "%s", buf) != EOF) {
switch(buf[0]) {
case '#': /* comment */
/* eat up rest of line */
fgets(buf, sizeof(buf), file);
break;
case 'v': /* v, vn, vt */
switch(buf[1]) {
case '\0': /* vertex */
/* eat up rest of line */
fgets(buf, sizeof(buf), file);
numvertices++;
break;
case 'n': /* normal */
/* eat up rest of line */
fgets(buf, sizeof(buf), file);
numnormals++;
break;
case 't': /* texcoord */
/* eat up rest of line */
fgets(buf, sizeof(buf), file);
numtexcoords++;
break;
default:
printf("glmFirstPass(): Unknown token \"%s\".\n", buf);
exit(1);
break;
}
break;
case 'm':
fgets(buf, sizeof(buf), file);
sscanf(buf, "%s %s", buf, buf);
model->mtllibname = strdup(buf);
glmReadMTL(model, buf);
break;
case 'u':
/* eat up rest of line */
fgets(buf, sizeof(buf), file);
break;
case 'g': /* group */
/* eat up rest of line */
fgets(buf, sizeof(buf), file);
#if SINGLE_STRING_GROUP_NAMES
sscanf(buf, "%s", buf);
#else
buf[strlen(buf)-1] = '\0'; /* nuke '\n' */
#endif
group = glmAddGroup(model, buf);
break;
case 'f': /* face */
v = n = t = 0;
fscanf(file, "%s", buf);
/* can be one of %d, %d//%d, %d/%d, %d/%d/%d %d//%d */
if (strstr(buf, "//")) {
/* v//n */
sscanf(buf, "%d//%d", &v, &n);
fscanf(file, "%d//%d", &v, &n);
fscanf(file, "%d//%d", &v, &n);
numtriangles++;
group->numtriangles++;
while(fscanf(file, "%d//%d", &v, &n) > 0) {
numtriangles++;
group->numtriangles++;
}
} else if (sscanf(buf, "%d/%d/%d", &v, &t, &n) == 3) {
/* v/t/n */
fscanf(file, "%d/%d/%d", &v, &t, &n);
fscanf(file, "%d/%d/%d", &v, &t, &n);
numtriangles++;
group->numtriangles++;
while(fscanf(file, "%d/%d/%d", &v, &t, &n) > 0) {
numtriangles++;
group->numtriangles++;
}
} else if (sscanf(buf, "%d/%d", &v, &t) == 2) {
/* v/t */
fscanf(file, "%d/%d", &v, &t);
fscanf(file, "%d/%d", &v, &t);
numtriangles++;
group->numtriangles++;
while(fscanf(file, "%d/%d", &v, &t) > 0) {
numtriangles++;
group->numtriangles++;
}
} else {
/* v */
fscanf(file, "%d", &v);
fscanf(file, "%d", &v);
numtriangles++;
group->numtriangles++;
while(fscanf(file, "%d", &v) > 0) {
numtriangles++;
group->numtriangles++;
}
}
break;
default:
/* eat up rest of line */
fgets(buf, sizeof(buf), file);
break;
}
}
/* set the stats in the model structure */
model->numvertices = numvertices;
model->numnormals = numnormals;
model->numtexcoords = numtexcoords;
model->numtriangles = numtriangles;
/* allocate memory for the triangles in each group */
group = model->groups;
while(group) {
group->triangles = (GLuint*)malloc(sizeof(GLuint) * group->numtriangles);
group->numtriangles = 0;
group = group->next;
}
}
/* glmSecondPass: second pass at a Wavefront OBJ file that gets all
* the data.
*
* model - properly initialized GLMmodel structure
* file - (fopen'd) file descriptor
*/
static GLvoid
glmSecondPass(GLMmodel* model, FILE* file)
{
GLuint numvertices; /* number of vertices in model */
GLuint numnormals; /* number of normals in model */
GLuint numtexcoords; /* number of texcoords in model */
GLuint numtriangles; /* number of triangles in model */
GLfloat* vertices; /* array of vertices */
GLfloat* normals; /* array of normals */
GLfloat* texcoords; /* array of texture coordinates */
GLMgroup* group; /* current group pointer */
GLuint material; /* current material */
GLuint v, n, t;
char buf[128];
/* set the pointer shortcuts */
vertices = model->vertices;
normals = model->normals;
texcoords = model->texcoords;
group = model->groups;
/* on the second pass through the file, read all the data into the
allocated arrays */
numvertices = numnormals = numtexcoords = 1;
numtriangles = 0;
material = 0;
while(fscanf(file, "%s", buf) != EOF) {
switch(buf[0]) {
case '#': /* comment */
/* eat up rest of line */
fgets(buf, sizeof(buf), file);
break;
case 'v': /* v, vn, vt */
switch(buf[1]) {
case '\0': /* vertex */
fscanf(file, "%f %f %f",
&vertices[3 * numvertices + 0],
&vertices[3 * numvertices + 1],
&vertices[3 * numvertices + 2]);
numvertices++;
break;
case 'n': /* normal */
fscanf(file, "%f %f %f",
&normals[3 * numnormals + 0],
&normals[3 * numnormals + 1],
&normals[3 * numnormals + 2]);
numnormals++;
break;
case 't': /* texcoord */
fscanf(file, "%f %f",
&texcoords[2 * numtexcoords + 0],
&texcoords[2 * numtexcoords + 1]);
numtexcoords++;
break;
}
break;
case 'u':
fgets(buf, sizeof(buf), file);
sscanf(buf, "%s %s", buf, buf);
group->material = material = glmFindMaterial(model, buf);
break;
case 'g': /* group */
/* eat up rest of line */
fgets(buf, sizeof(buf), file);
#if SINGLE_STRING_GROUP_NAMES
sscanf(buf, "%s", buf);
#else
buf[strlen(buf)-1] = '\0'; /* nuke '\n' */
#endif
group = glmFindGroup(model, buf);
group->material = material;
break;
case 'f': /* face */
v = n = t = 0;
fscanf(file, "%s", buf);
/* can be one of %d, %d//%d, %d/%d, %d/%d/%d %d//%d */
if (strstr(buf, "//")) {
/* v//n */
sscanf(buf, "%d//%d", &v, &n);
T(numtriangles).vindices[0] = v;
T(numtriangles).nindices[0] = n;
fscanf(file, "%d//%d", &v, &n);
T(numtriangles).vindices[1] = v;
T(numtriangles).nindices[1] = n;
fscanf(file, "%d//%d", &v, &n);
T(numtriangles).vindices[2] = v;
T(numtriangles).nindices[2] = n;
group->triangles[group->numtriangles++] = numtriangles;
numtriangles++;
while(fscanf(file, "%d//%d", &v, &n) > 0) {
T(numtriangles).vindices[0] = T(numtriangles-1).vindices[0];
T(numtriangles).nindices[0] = T(numtriangles-1).nindices[0];
T(numtriangles).vindices[1] = T(numtriangles-1).vindices[2];
T(numtriangles).nindices[1] = T(numtriangles-1).nindices[2];
T(numtriangles).vindices[2] = v;
T(numtriangles).nindices[2] = n;
group->triangles[group->numtriangles++] = numtriangles;
numtriangles++;
}
} else if (sscanf(buf, "%d/%d/%d", &v, &t, &n) == 3) {
/* v/t/n */
T(numtriangles).vindices[0] = v;
T(numtriangles).tindices[0] = t;
T(numtriangles).nindices[0] = n;
fscanf(file, "%d/%d/%d", &v, &t, &n);
T(numtriangles).vindices[1] = v;
T(numtriangles).tindices[1] = t;
T(numtriangles).nindices[1] = n;
fscanf(file, "%d/%d/%d", &v, &t, &n);
T(numtriangles).vindices[2] = v;
T(numtriangles).tindices[2] = t;
T(numtriangles).nindices[2] = n;
group->triangles[group->numtriangles++] = numtriangles;
numtriangles++;
while(fscanf(file, "%d/%d/%d", &v, &t, &n) > 0) {
T(numtriangles).vindices[0] = T(numtriangles-1).vindices[0];
T(numtriangles).tindices[0] = T(numtriangles-1).tindices[0];
T(numtriangles).nindices[0] = T(numtriangles-1).nindices[0];
T(numtriangles).vindices[1] = T(numtriangles-1).vindices[2];
T(numtriangles).tindices[1] = T(numtriangles-1).tindices[2];
T(numtriangles).nindices[1] = T(numtriangles-1).nindices[2];
T(numtriangles).vindices[2] = v;
T(numtriangles).tindices[2] = t;
T(numtriangles).nindices[2] = n;
group->triangles[group->numtriangles++] = numtriangles;
numtriangles++;
}
} else if (sscanf(buf, "%d/%d", &v, &t) == 2) {
/* v/t */
T(numtriangles).vindices[0] = v;
T(numtriangles).tindices[0] = t;
fscanf(file, "%d/%d", &v, &t);
T(numtriangles).vindices[1] = v;
T(numtriangles).tindices[1] = t;
fscanf(file, "%d/%d", &v, &t);
T(numtriangles).vindices[2] = v;
T(numtriangles).tindices[2] = t;
group->triangles[group->numtriangles++] = numtriangles;
numtriangles++;
while(fscanf(file, "%d/%d", &v, &t) > 0) {
T(numtriangles).vindices[0] = T(numtriangles-1).vindices[0];
T(numtriangles).tindices[0] = T(numtriangles-1).tindices[0];
T(numtriangles).vindices[1] = T(numtriangles-1).vindices[2];
T(numtriangles).tindices[1] = T(numtriangles-1).tindices[2];
T(numtriangles).vindices[2] = v;
T(numtriangles).tindices[2] = t;
group->triangles[group->numtriangles++] = numtriangles;
numtriangles++;
}
} else {
/* v */
sscanf(buf, "%d", &v);
T(numtriangles).vindices[0] = v;
fscanf(file, "%d", &v);
T(numtriangles).vindices[1] = v;
fscanf(file, "%d", &v);
T(numtriangles).vindices[2] = v;
group->triangles[group->numtriangles++] = numtriangles;
numtriangles++;
while(fscanf(file, "%d", &v) > 0) {
T(numtriangles).vindices[0] = T(numtriangles-1).vindices[0];
T(numtriangles).vindices[1] = T(numtriangles-1).vindices[2];
T(numtriangles).vindices[2] = v;
group->triangles[group->numtriangles++] = numtriangles;
numtriangles++;
}
}
break;
default:
/* eat up rest of line */
fgets(buf, sizeof(buf), file);
break;
}
}
#if 0
/* announce the memory requirements */
printf(" Memory: %d bytes\n",
numvertices * 3*sizeof(GLfloat) +
numnormals * 3*sizeof(GLfloat) * (numnormals ? 1 : 0) +
numtexcoords * 3*sizeof(GLfloat) * (numtexcoords ? 1 : 0) +
numtriangles * sizeof(GLMtriangle));
#endif
}
/* public functions */
/* glmUnitize: "unitize" a model by translating it to the origin and
* scaling it to fit in a unit cube around the origin. Returns the
* scalefactor used.
*
* model - properly initialized GLMmodel structure
*/
GLfloat
glmUnitize(GLMmodel* model)
{
GLuint i;
GLfloat maxx, minx, maxy, miny, maxz, minz;
GLfloat cx, cy, cz, w, h, d;
GLfloat scale;
assert(model);
assert(model->vertices);
/* get the max/mins */
maxx = minx = model->vertices[3 + 0];
maxy = miny = model->vertices[3 + 1];
maxz = minz = model->vertices[3 + 2];
for (i = 1; i <= model->numvertices; i++) {
if (maxx < model->vertices[3 * i + 0])
maxx = model->vertices[3 * i + 0];
if (minx > model->vertices[3 * i + 0])
minx = model->vertices[3 * i + 0];
if (maxy < model->vertices[3 * i + 1])
maxy = model->vertices[3 * i + 1];
if (miny > model->vertices[3 * i + 1])
miny = model->vertices[3 * i + 1];
if (maxz < model->vertices[3 * i + 2])
maxz = model->vertices[3 * i + 2];
if (minz > model->vertices[3 * i + 2])
minz = model->vertices[3 * i + 2];
}
/* calculate model width, height, and depth */
w = glmAbs(maxx) + glmAbs(minx);
h = glmAbs(maxy) + glmAbs(miny);
d = glmAbs(maxz) + glmAbs(minz);
/* calculate center of the model */
cx = (maxx + minx) / 2.0;
cy = (maxy + miny) / 2.0;
cz = (maxz + minz) / 2.0;
/* calculate unitizing scale factor */
scale = 2.0 / glmMax(glmMax(w, h), d);
/* translate around center then scale */
for (i = 1; i <= model->numvertices; i++) {
model->vertices[3 * i + 0] -= cx;
model->vertices[3 * i + 1] -= cy;
model->vertices[3 * i + 2] -= cz;
model->vertices[3 * i + 0] *= scale;
model->vertices[3 * i + 1] *= scale;
model->vertices[3 * i + 2] *= scale;
}
return scale;
}
/* glmDimensions: Calculates the dimensions (width, height, depth) of
* a model.
*
* model - initialized GLMmodel structure
* dimensions - array of 3 GLfloats (GLfloat dimensions[3])
*/
GLvoid
glmDimensions(GLMmodel* model, GLfloat* dimensions)
{
GLuint i;
GLfloat maxx, minx, maxy, miny, maxz, minz;
assert(model);
assert(model->vertices);
assert(dimensions);
/* get the max/mins */
maxx = minx = model->vertices[3 + 0];
maxy = miny = model->vertices[3 + 1];
maxz = minz = model->vertices[3 + 2];
for (i = 1; i <= model->numvertices; i++) {
if (maxx < model->vertices[3 * i + 0])
maxx = model->vertices[3 * i + 0];
if (minx > model->vertices[3 * i + 0])
minx = model->vertices[3 * i + 0];
if (maxy < model->vertices[3 * i + 1])
maxy = model->vertices[3 * i + 1];
if (miny > model->vertices[3 * i + 1])
miny = model->vertices[3 * i + 1];
if (maxz < model->vertices[3 * i + 2])
maxz = model->vertices[3 * i + 2];
if (minz > model->vertices[3 * i + 2])
minz = model->vertices[3 * i + 2];
}
/* calculate model width, height, and depth */
dimensions[0] = glmAbs(maxx) + glmAbs(minx);
dimensions[1] = glmAbs(maxy) + glmAbs(miny);
dimensions[2] = glmAbs(maxz) + glmAbs(minz);
}
/* glmScale: Scales a model by a given amount.
*
* model - properly initialized GLMmodel structure
* scale - scalefactor (0.5 = half as large, 2.0 = twice as large)
*/
GLvoid
glmScale(GLMmodel* model, GLfloat scale)
{
GLuint i;
for (i = 1; i <= model->numvertices; i++) {
model->vertices[3 * i + 0] *= scale;
model->vertices[3 * i + 1] *= scale;
model->vertices[3 * i + 2] *= scale;
}
}
/* glmReverseWinding: Reverse the polygon winding for all polygons in
* this model. Default winding is counter-clockwise. Also changes
* the direction of the normals.
*
* model - properly initialized GLMmodel structure
*/
GLvoid
glmReverseWinding(GLMmodel* model)
{
GLuint i, swap;
assert(model);
for (i = 0; i < model->numtriangles; i++) {
swap = T(i).vindices[0];
T(i).vindices[0] = T(i).vindices[2];
T(i).vindices[2] = swap;
if (model->numnormals) {
swap = T(i).nindices[0];
T(i).nindices[0] = T(i).nindices[2];
T(i).nindices[2] = swap;
}
if (model->numtexcoords) {
swap = T(i).tindices[0];
T(i).tindices[0] = T(i).tindices[2];
T(i).tindices[2] = swap;
}
}
/* reverse facet normals */
for (i = 1; i <= model->numfacetnorms; i++) {
model->facetnorms[3 * i + 0] = -model->facetnorms[3 * i + 0];
model->facetnorms[3 * i + 1] = -model->facetnorms[3 * i + 1];
model->facetnorms[3 * i + 2] = -model->facetnorms[3 * i + 2];
}
/* reverse vertex normals */
for (i = 1; i <= model->numnormals; i++) {
model->normals[3 * i + 0] = -model->normals[3 * i + 0];
model->normals[3 * i + 1] = -model->normals[3 * i + 1];
model->normals[3 * i + 2] = -model->normals[3 * i + 2];
}
}
/* glmFacetNormals: Generates facet normals for a model (by taking the
* cross product of the two vectors derived from the sides of each
* triangle). Assumes a counter-clockwise winding.
*
* model - initialized GLMmodel structure
*/
GLvoid
glmFacetNormals(GLMmodel* model)
{
GLuint i;
GLfloat u[3];
GLfloat v[3];
assert(model);
assert(model->vertices);
/* clobber any old facetnormals */
if (model->facetnorms)
free(model->facetnorms);
/* allocate memory for the new facet normals */
model->numfacetnorms = model->numtriangles;
model->facetnorms = (GLfloat*)malloc(sizeof(GLfloat) *
3 * (model->numfacetnorms + 1));
for (i = 0; i < model->numtriangles; i++) {
model->triangles[i].findex = i+1;
u[0] = model->vertices[3 * T(i).vindices[1] + 0] -
model->vertices[3 * T(i).vindices[0] + 0];
u[1] = model->vertices[3 * T(i).vindices[1] + 1] -
model->vertices[3 * T(i).vindices[0] + 1];
u[2] = model->vertices[3 * T(i).vindices[1] + 2] -
model->vertices[3 * T(i).vindices[0] + 2];
v[0] = model->vertices[3 * T(i).vindices[2] + 0] -
model->vertices[3 * T(i).vindices[0] + 0];
v[1] = model->vertices[3 * T(i).vindices[2] + 1] -
model->vertices[3 * T(i).vindices[0] + 1];
v[2] = model->vertices[3 * T(i).vindices[2] + 2] -
model->vertices[3 * T(i).vindices[0] + 2];
glmCross(u, v, &model->facetnorms[3 * (i+1)]);
glmNormalize(&model->facetnorms[3 * (i+1)]);
}
}
/* glmVertexNormals: Generates smooth vertex normals for a model.
* First builds a list of all the triangles each vertex is in. Then
* loops through each vertex in the the list averaging all the facet
* normals of the triangles each vertex is in. Finally, sets the
* normal index in the triangle for the vertex to the generated smooth
* normal. If the dot product of a facet normal and the facet normal
* associated with the first triangle in the list of triangles the
* current vertex is in is greater than the cosine of the angle
* parameter to the function, that facet normal is not added into the
* average normal calculation and the corresponding vertex is given
* the facet normal. This tends to preserve hard edges. The angle to
* use depends on the model, but 90 degrees is usually a good start.
*
* model - initialized GLMmodel structure
* angle - maximum angle (in degrees) to smooth across
*/
GLvoid