Overview Function List GLOD Web Site


glodFillArrays - Rather than drawing a patch, this places what would be drawn into the current OpenGL vertex/normal/color/texcoord arrays.


void glodFillArrays(GLuint object_name, GLuint patch_name)


object_name, patch_name
Selects the object and patch to read back.


glodFillArrays() is used to ``see'' what GLOD will draw if you were to call glodDrawPatch() . To read back the current state of an object using glodFillArrays() , you usually:

  • Call glodGetObjectParameter(obj, patch, GLOD_PATCH_SIZES, dst_arry) to obtain the number of vertices and indices (=triangles*3) that glodFillArrays() or glodDrawPatch() will issue for this patch.

  • Allocate buffers for the vertices and any other data that you want to read back. You must allocate space for 3*num_indices vertices. If you want to achieve better space utilization, consider using the glodFillElements() call.

  • Set the vertex array state (glVertexPointer etc) to match your allocated buffers.

  • Call glodFillArrays()

When this call returns, the currently set array pointers will have been filled in with the current GLOD cut. It is critical that the buffers to which the pointers refer are large enough to accomodate the cut. Otherwise, memory corruption will occur.


The following code reads back the zero-th patch in object 0. It is assumed that the object consists of 1 patch and that the zero-th patch is named zero. If these assumptions do not hold, you will need an extra layer of indirection that uses the glodGetObjectParamiv GLOD_NUM_PATCHES and GLOD_PATCH_NAMES feature to make this code fully generic.

  // get the size of this patch
  GLfloat* vert_buf, *normal_buf;
  int numIndices,numVerts;
  int dims[2];
  glodGetObjectParamiv(0, GLOD_PATCH_SIZES, dims);
  numIndices = dims[0];
  numVerts   = dims[1]; // we ignore this value for glodFillArrays
  vert_buf = malloc(sizeof(float) * (numIndices*3));
  normal_buf = malloc(sizeof(float) * (numIndices*3));
  glVertexPointer(3, GL_FLOAT, 0, vert_buf);
  glNormalPointer(GL_FLOAT, 0, normal_buf);
  glFillArrays(0, 0);
  // now, vert_buf and normal_buf contain a copy of 
  // object 0, patch 0's current geometry


GLOD_INVALID_NAME is generated if an object of the specified name does not exist
GLOD_INVALID_STATE is generated if the object has not been built yet.
GLOD_INVALID_PATCH is generated if the object does not have a patch of the specified name.

Last modified: 06/10/04 06:32:24 PM