glm.c

嵌入式GUI OpenGL源代码。OpenGL是嵌入式开发中常用的一种GUI系统。

  /* 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
glmVertexNormals(GLMmodel* model, GLfloat angle)
{
  GLMnode*  node;
  GLMnode*  tail;
  GLMnode** members;
  GLfloat*  normals;
  GLuint    numnormals;
  GLfloat   average[3];
  GLfloat   dot, cos_angle;
  GLuint    i, avg;

  assert(model);
  assert(model->facetnorms);

  /* calculate the cosine of the angle (in degrees) */
  cos_angle = cos(angle * M_PI / 180.0);

  /* nuke any previous normals */
  if (model->normals)
    free(model->normals);

  /* allocate space for new normals */
  model->numnormals = model->numtriangles * 3; /* 3 normals per triangle */
  model->normals = (GLfloat*)malloc(sizeof(GLfloat)* 3* (model->numnormals+1));

  /* allocate a structure that will hold a linked list of triangle
     indices for each vertex */
  members = (GLMnode**)malloc(sizeof(GLMnode*) * (model->numvertices + 1));
  for (i = 1; i <= model->numvertices; i++)
    members[i] = NULL;
  
  /* for every triangle, create a node for each vertex in it */
  for (i = 0; i < model->numtriangles; i++) {
    node = (GLMnode*)malloc(sizeof(GLMnode));
    node->index = i;
    node->next  = members[T(i).vindices[0]];
    members[T(i).vindices[0]] = node;

    node = (GLMnode*)malloc(sizeof(GLMnode));
    node->index = i;
    node->next  = members[T(i).vindices[1]];
    members[T(i).vindices[1]] = node;

    node = (GLMnode*)malloc(sizeof(GLMnode));
    node->index = i;
    node->next  = members[T(i).vindices[2]];
    members[T(i).vindices[2]] = node;
  }

  /* calculate the average normal for each vertex */
  numnormals = 1;
  for (i = 1; i <= model->numvertices; i++) {
    /* calculate an average normal for this vertex by averaging the
       facet normal of every triangle this vertex is in */
    node = members[i];
    if (!node)
      fprintf(stderr, "glmVertexNormals(): vertex w/o a triangle\n");
    average[0] = 0.0; average[1] = 0.0; average[2] = 0.0;
    avg = 0;
    while (node) {
      /* only average if the dot product of the angle between the two
         facet normals is greater than the cosine of the threshold
         angle -- or, said another way, the angle between the two
         facet normals is less than (or equal to) the threshold angle */
      dot = glmDot(&model->facetnorms[3 * T(node->index).findex],
 		    &model->facetnorms[3 * T(members[i]->index).findex]);
      if (dot > cos_angle) {
	node->averaged = GL_TRUE;
	average[0] += model->facetnorms[3 * T(node->index).findex + 0];
	average[1] += model->facetnorms[3 * T(node->index).findex + 1];
	average[2] += model->facetnorms[3 * T(node->index).findex + 2];
	avg = 1;			/* we averaged at least one normal! */
      } else {
	node->averaged = GL_FALSE;
      }
      node = node->next;
    }

    if (avg) {
      /* normalize the averaged normal */
      glmNormalize(average);

      /* add the normal to the vertex normals list */
      model->normals[3 * numnormals + 0] = average[0];
      model->normals[3 * numnormals + 1] = average[1];
      model->normals[3 * numnormals + 2] = average[2];
      avg = numnormals;
      numnormals++;
    }

    /* set the normal of this vertex in each triangle it is in */
    node = members[i];
    while (node) {
      if (node->averaged) {
	/* if this node was averaged, use the average normal */
	if (T(node->index).vindices[0] == i)
	  T(node->index).nindices[0] = avg;
	else if (T(node->index).vindices[1] == i)
	  T(node->index).nindices[1] = avg;
	else if (T(node->index).vindices[2] == i)
	  T(node->index).nindices[2] = avg;
      } else {
	/* if this node wasn't averaged, use the facet normal */
	model->normals[3 * numnormals + 0] = 
	  model->facetnorms[3 * T(node->index).findex + 0];
	model->normals[3 * numnormals + 1] = 
	  model->facetnorms[3 * T(node->index).findex + 1];
	model->normals[3 * numnormals + 2] = 
	  model->facetnorms[3 * T(node->index).findex + 2];
	if (T(node->index).vindices[0] == i)
	  T(node->index).nindices[0] = numnormals;
	else if (T(node->index).vindices[1] == i)
	  T(node->index).nindices[1] = numnormals;
	else if (T(node->index).vindices[2] == i)
	  T(node->index).nindices[2] = numnormals;
	numnormals++;
      }
      node = node->next;
    }
  }
  
  model->numnormals = numnormals - 1;

  /* free the member information */
  for (i = 1; i <= model->numvertices; i++) {
    node = members[i];
    while (node) {
      tail = node;
      node = node->next;
      free(tail);
    }
  }
  free(members);

  /* pack the normals array (we previously allocated the maximum
     number of normals that could possibly be created (numtriangles *
     3), so get rid of some of them (usually alot unless none of the
     facet normals were averaged)) */
  normals = model->normals;
  model->normals = (GLfloat*)malloc(sizeof(GLfloat)* 3* (model->numnormals+1));
  for (i = 1; i <= model->numnormals; i++) {
    model->normals[3 * i + 0] = normals[3 * i + 0];
    model->normals[3 * i + 1] = normals[3 * i + 1];
    model->normals[3 * i + 2] = normals[3 * i + 2];
  }
  free(normals);
}


/* glmLinearTexture: Generates texture coordinates according to a
 * linear projection of the texture map.  It generates these by
 * linearly mapping the vertices onto a square.
 *
 * model - pointer to initialized GLMmodel structure
 */
GLvoid
glmLinearTexture(GLMmodel* model)
{
  GLMgroup *group;
  GLfloat dimensions[3];
  GLfloat x, y, scalefactor;
  GLuint i;
  
  assert(model);

  if (model->texcoords)
    free(model->texcoords);
  model->numtexcoords = model->numvertices;
  model->texcoords=(GLfloat*)malloc(sizeof(GLfloat)*2*(model->numtexcoords+1));
  
  glmDimensions(model, dimensions);
  scalefactor = 2.0 / 
    glmAbs(glmMax(glmMax(dimensions[0], dimensions[1]), dimensions[2]));

  /* do the calculations */
  for(i = 1; i <= model->numvertices; i++) {
    x = model->vertices[3 * i + 0] * scalefactor;
    y = model->vertices[3 * i + 2] * scalefactor;
    model->texcoords[2 * i + 0] = (x + 1.0) / 2.0;
    model->texcoords[2 * i + 1] = (y + 1.0) / 2.0;
  }
  
  /* go through and put texture coordinate indices in all the triangles */
  group = model->groups;
  while(group) {
    for(i = 0; i < group->numtriangles; i++) {
      T(group->triangles[i]).tindices[0] = T(group->triangles[i]).vindices[0];
      T(group->triangles[i]).tindices[1] = T(group->triangles[i]).vindices[1];
      T(group->triangles[i]).tindices[2] = T(group->triangles[i]).vindices[2];
    }    
    group = group->next;
  }

#if 0
  printf("glmLinearTexture(): generated %d linear texture coordinates\n",
	  model->numtexcoords);
#endif
}

/* glmSpheremapTexture: Generates texture coordinates according to a
 * spherical projection of the texture map.  Sometimes referred to as
 * spheremap, or reflection map texture coordinates.  It generates
 * these by using the normal to calculate where that vertex would map
 * onto a sphere.  Since it is impossible to map something flat
 * perfectly onto something spherical, there is distortion at the
 * poles.  This particular implementation causes the poles along the X
 * axis to be distorted.
 *
 * model - pointer to initialized GLMmodel structure
 */
GLvoid
glmSpheremapTexture(GLMmodel* model)
{
  GLMgroup* group;
  GLfloat theta, phi, rho, x, y, z, r;
  GLuint i;
  
  assert(model);
  assert(model->normals);

  if (model->texcoords)
    free(model->texcoords);
  model->numtexcoords = model->numnormals;
  model->texcoords=(GLfloat*)malloc(sizeof(GLfloat)*2*(model->numtexcoords+1));
     
  for (i = 1; i <= model->numnormals; i++) {
    z = model->normals[3 * i + 0];	/* re-arrange for pole distortion */
    y = model->normals[3 * i + 1];
    x = model->normals[3 * i + 2];
    r = sqrt((x * x) + (y * y));
    rho = sqrt((r * r) + (z * z));
      
    if(r == 0.0) {
	theta = 0.0;
	phi = 0.0;
    } else {
      if(z == 0.0)
	phi = 3.14159265 / 2.0;
      else
	phi = acos(z / rho);

      if(y == 0.0)
	theta = 3.141592365 / 2.0;
      else
	theta = asin(y / r) + (3.14159265 / 2.0);
    }
    
    model->texcoords[2 * i + 0] = theta / 3.14159265;
    model->texcoords[2 * i + 1] = phi / 3.14159265;
  }
  
  /* go through and put texcoord indices in all the triangles */
  group = model->groups;
  while(group) {
    for (i = 0; i < group->numtriangles; i++) {
      T(group->triangles[i]).tindices[0] = T(group->triangles[i]).nindices[0];
      T(group->triangles[i]).tindices[1] = T(group->triangles[i]).nindices[1];
      T(group->triangles[i]).tindices[2] = T(group->triangles[i]).nindices[2];
    }
    group = group->next;
  }
}

/* glmDelete: Deletes a GLMmodel structure.
 *
 * model - initialized GLMmodel structure
 */
GLvoid
glmDelete(GLMmodel* model)
{
  GLMgroup* group;
  GLuint i;

  assert(model);

  if (model->pathname)   free(model->pathname);
  if (model->mtllibname) free(model->mtllibname);
  if (model->vertices)   free(model->vertices);
  if (model->normals)    free(model->normals);
  if (model->texcoords)  free(model->texcoords);
  if (model->facetnorms) free(model->facetnorms);
  if (model->triangles)  free(model->triangles);
  if (model->materials) {
    for (i = 0; i < model->nummaterials; i++)
      free(model->materials[i].name);
  }
  free(model->materials);
  while(model->groups) {
    group = model->groups;
    model->groups = model->groups->next;
    free(group->name);
    free(group->triangles);
    free(group);
  }

  free(model);
}

/* glmReadOBJ: Reads a model description from a Wavefront .OBJ file.
 * Returns a pointer to the created object which should be free'd with
 * glmDelete().
 *
 * filename - name of the file containing the Wavefront .OBJ format data.  
 */
GLMmodel* 
glmReadOBJ(char* filename)
{
  GLMmodel* model;
  FILE*     file;

  /* open the file */
  file = fopen(filename, "r");
  if (!file) {
    fprintf(stderr, "glmReadOBJ() failed: can't open data file \"%s\".\n",
	    filename);
    exit(1);
  }

  /* allocate a new model */
  model = (GLMmodel*)malloc(sizeof(GLMmodel));
  model->pathname      = strdup(filename);
  model->mtllibname    = NULL;
  model->numvertices   = 0;
  model->vertices      = NULL;
  model->numnormals    = 0;
  model->normals       = NULL;
  model->numtexcoords  = 0;
  model->texcoords     = NULL;
  model->numfacetnorms = 0;
  model->facetnorms    = NULL;
  model->numtriangles  = 0;
  model->triangles     = NULL;
  model->nummaterials  = 0;
  model->materials     = NULL;
  model->numgroups     = 0;
  model->groups        = NULL;
  model->position[0]   = 0.0;
  model->position[1]   = 0.0;
  model->position[2]   = 0.0;

  /* make a first pass through the file to get a count of the number
     of vertices, normals, texcoords & triangles */
  glmFirstPass(model, file);

  /* allocate memory */
  model->vertices = (GLfloat*)malloc(sizeof(GLfloat) *
				     3 * (model->numvertices + 1));
  model->triangles = (GLMtriangle*)malloc(sizeof(GLMtriangle) *
					  model->numtriangles);
  if (model->numnormals) {
    model->normals = (GLfloat*)malloc(sizeof(GLfloat) *
				      3 * (model->numnormals + 1));
  }
  if (model->numtexcoords) {
    model->texcoords = (GLfloat*)malloc(sizeof(GLfloat) *
					2 * (model->numtexcoords + 1));
  }

  /* rewind to beginning of file and read in the data this pass */
  rewind(file);

  glmSecondPass(model, file);

  /* close the file */
  fclose(file);

  return model;
}

/* glmWriteOBJ: Writes a model description in Wavefront .OBJ format to
 * a file.
 *
 * model    - initialized GLMmodel structure
 * filename - name of the file to write the Wavefront .OBJ format data to
 * mode     - a bitwise or of values describing what is written to the file
 *            GLM_NONE     -  render with only vertices
 *            GLM_FLAT     -  render with facet normals
 *            GLM_SMOOTH   -  render with vertex normals
 *            GLM_TEXTURE  -  render with texture coords
 *            GLM_COLOR    -  render with colors (color material)