Re: [PyOpenGL-Users] glVertexAttribPointer Problem

[Alejandro S. <as...@gm...>]

Hello Thomas,

On Jan 30, 2011, at 3:19 PM, Thomas <p_t...@gm...> wrote:

> Hello,
> 
> I'm trying to use glVertexAttribPointer and interleaved vertex data.
> 
> // simple coordinate cross: vertex0, color0, ...
> data = [0.0, 0.0, 0.0, 1.0, 0.0, 0.0, # x0
>              1.0, 0.0, 0.0, 1.0, 0.0, 0.0, # x1
>              0.0, 0.0, 0.0, 0.0, 1.0, 0.0, # y0
>              0.0, 1.0, 0.0, 0.0, 1.0, 0.0, # y1
>              0.0, 0.0, 0.0, 0.0, 0.0, 1.0, # z0
>              0.0, 0.0, 1.0, 0.0, 0.0, 1.0] # z1
> 
> buffer = glGenBuffers(1)
> glBindBuffer(GL_ARRAY_BUFFER, buffer)
> glBufferData(GL_ARRAY_BUFFER, numpy.array(cross, numpy.float32), 
> GL_STATIC_DRAW)
> 
> # attributes are queried by glGetAttribLocation after shaders are linked
> glVertexAttribPointer(attributes['coord'], GLint(3), GL_FLOAT, GL_FALSE, 
> GLsizei(6 * 4), ctypes.c_void_p(0))
> glVertexAttribPointer(attributes['color'], GLint(3), GL_FLOAT, GL_FALSE, 
> GLsizei(6 * 4), ctypes.c_void_p(3))

I'm not 100% sure, but shouldn't this last call to c_void_p receive 3*4 instead of 3? Please check whether a byte offset is expected here by OpenGL. 

Good luck,
Alejandro.-

> 
> for index in attributes.values():
>             glEnableVertexAttribArray(index)
> 
> In my vertex shader I have:
> attribute vec3 coord;
> attribute vec3 color;
> 
> Vertex data is correct, but "vec3 color" is always (0.0, 0.0, 0.0)
> 
> Is it a problem with pyopengl or did I miss something in my setup?
> 
> -Thomas
> 
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