Re: [PyOpenGL-Users] best way to set up matrices and vertex arrays?

[Dan H. <Dan...@no...>]

Kolja Kaehler wrote:
> Does anyone here have some advice for me on these matters? Maybe I am 
> just missing “the obvious way” to organize these things.

Hi Kolja,

I haven't had any problems using NumPy's row-major arrays with PyOpenGL. 
For instance if you have a row-major NumPy array of dtype [ ( "x", 
np.float32 ), ( "y", np.float32 ) ], you can pass the array directly to 
PyOpenGL by putting it in a vertex buffer object and then using 
glVertexPointer( 2, gl.GL_FLOAT, 0, None ) to tell GL to expect 2 floats 
for each vertex. The same principle works for 3D as well.

And if you'd like to store several pieces of NumPy array data together, 
then you can just use a recarray, and then pass an individual "member" 
array to PyOpenGL at any point you want.

Perhaps you can give an example of what you're trying to do where the 
row-major/column-major distinction gets in the way?

There really isn't a good way to dynamically grow a vertex array with 
NumPy. Some options are:

   * Use numpy.resize(), which just returns a new, larger array copy.
   * Use numpy.ndarray.resize(), which can only resize if there are no 
other references to the array.
   * Accumulate and grow with a data structure other than a NumPy array, 
and then convert to a NumPy array when you're done growing. Some 
candidates are a Python list (slow), or if you're willing to use Cython 
or C, then accumulate in a C array with realloc() for growing.

I haven't really used NumPy matrices, so I'll let someone else comment 
on that one.

Dan