Vertex buffer objects in PyOpenGL

Posted on 31 Aug 2007. in development games python

Decided to move some of my vertex array code over to ARB_vertex_buffer_object, to see if I could get a bit of a speed boost out of PyOpenGL. Much to my dismay, these functions don’t have the sexy extension wrappers I talked about before, so it was a bit of a chore to get it all working.

Here’s a little wrapper class I wrote to make things easier:

    from OpenGL.GL import *
    from OpenGL.raw import GL
    from OpenGL.arrays import ArrayDatatype as ADT

    class VertexBuffer(object):

        def __init__(self, data, usage):
            self.buffer = GL.GLuint(0)
            glGenBuffers(1, self.buffer)
            self.buffer = self.buffer.value
            glBindBuffer(GL_ARRAY_BUFFER_ARB, self.buffer)
            glBufferData(GL_ARRAY_BUFFER_ARB, ADT.arrayByteCount(data),
                         ADT.voidDataPointer(data), usage)

        def __del__(self):
            glDeleteBuffers(1, GL.GLuint(self.buffer))

        def bind(self):
            glBindBuffer(GL_ARRAY_BUFFER_ARB, self.buffer)

        def bind_vertexes(self, size, type, stride=0):
            self.bind()
            glVertexPointer(size, type, stride, None)

        ... snipped for length ...

Download buffers.py.

So, how to use it? Let’s say you have a Python list with a bunch of vertexes with float x, y, and z components:

    verts = [[x, y, z], [x, y, z], [x, y, z], ...]

You’ll have to use NumPy or an equivalent to convert it to a PyOpenGL compatible array:

    import numpy
    numpy_verts = numpy.array(verts, dtype=numpy.float32)

Create the VertexBuffer object with it:

    buffer = VertexBuffer(numpy_verts, GL_STATIC_DRAW)

Use it in your day to day rendering:

    glEnableClientState(GL_VERTEX_ARRAY)
    buffer.bind_vertexes(3, GL_FLOAT)
    glDrawElementsui(GL_TRIANGLES, indexes)

They’re not shown in the snippet, but I’ve also defined bind_colors, bind_edgeflags, bind_indexes, bind_normals, and bind_texcoords, as shortcuts for the rest of the GL array functions.

ltslashgt

Vertex buffer objects in PyOpenGL