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)
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));
glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_NORMAL_ARRAY);
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
