Re: [PyOpenGL-Users] VBO help and performance

[Wakefield, R. <rjw...@en...>]

I finally managed to get things working with the VBOs (big thanks to Ian Mallett for the tip on the VBO class), but I have one question left.  I noticed in the pyOpenGL spec that glVertexPointer (and the others) are deprecated and scheduled to be removed in the newer OpenGL versions.  Is the only replacement using a GLSL shader?  If not, what's the other option.  

I found a helpful example in the mail archive here: http://blog.gmane.org/gmane.comp.python.opengl.user/month=20090801 using that (also see vboattrib.py by clicking on '17 comments' for Josh Davis; you'll have to rename the bin file to .py), but I'm not really sure how to apply this to simple tiling.  What is the quickest way to set vloc/tloc so OpenGL know that these are the vertices/textures respectively so the code below works?

# main body of drawVBO in the draw loop
    vbo.bind()
    glVertexAttribPointer(vloc, 2, GL_FLOAT, False, 0, vbo) # vertex location, start of VBO
    glVertexAttribPointer(tloc, 2, GL_FLOAT, False, 0, vbo + (len(vbo)/2*4)) #texture location, halfway through VBO
    glEnableVertexAttribArray(vloc)
    glEnableVertexAttribArray(tloc)
    glDrawArrays(GL_TRIANGLES, 0, len(vbo)/2)
    glDisableVertexAttribArray(vloc)
    glDisableVertexAttribArray(tloc)
    vbo.unbind()

For reference, the working code I use with vertex pointers is below.  My earlier problem was apparently doing the glBufferData call wrong, and in case this helps anyone else the VBO class is a helpful way to outsource the job.  By the way, does interleaving data offer a good performance gain over a linear VBO (list of verts, then colors, then textures)?

# in the initialization; vbo3 is passed to drawVBO later.  
    dat = verts[:] + textures[:] # a flat list works fine
    vbo3 = VBO(numpy.asarray(dat, 'f'), GL_STATIC_DRAW, GL_ARRAY_BUFFER)
    
def drawVBO(texid, vbo):
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)
    glBindTexture( GL_TEXTURE_2D, texid)

    vbo.bind()
    glEnableClientState(GL_VERTEX_ARRAY)
    glEnableClientState(GL_TEXTURE_COORD_ARRAY)
    glVertexPointer(2, GL_FLOAT, 0, vbo)
    glTexCoordPointer(2, GL_FLOAT, 0, vbo + (len(vbo)/2*4)) # the *4 accounts for sizeof(float)
    glDrawArrays(GL_TRIANGLES, 0, len(vbo)/2)
    glDisableClientState(GL_TEXTURE_COORD_ARRAY)
    glDisableClientState(GL_VERTEX_ARRAY)
    vbo.unbind()

    glFlush()
    glFinish()
    ''' I'm using pygame, so I pygame put it all on the screen; GLUT can do the same '''
    pygame.display.flip()