// Add a line to glm.h as follows:

typedef struct _GLMmodel {
  char*    pathname;			/* path to this model */
  char*    mtllibname;			/* name of the material library */

  GLuint   numvertices;			/* number of vertices in model */
  GLfloat* vertices;			/* array of vertices  */
  GLfloat* normArray;   // ADD THIS LINE.

  GLuint   numnormals;			/* number of normals in model */
  GLfloat* normals;			/* array of normals */


// Use "normArray" instead of "normals" for your normal array
//   when using in a vertex array.


// Replace your glmVertexNormals in glm.cpp by this:

GLvoid
glmVertexNormals(GLMmodel* model, GLfloat angle)
{
  GLMnode*  node;
  GLMnode*  tail;
  GLMnode** members;
  GLfloat*  normals;
  GLuint    numnormals, tmpCount;
  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));
  model->normArray = (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 */
  tmpCount = 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++;
    }

	glmNormalize(average);
	model->normArray[3 * tmpCount + 0] = average[0];
	model->normArray[3 * tmpCount + 1] = average[1];
	model->normArray[3 * tmpCount + 2] = average[2];
	tmpCount++;

    /* 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);
}