pyopengl-users

[PyOpenGL-Users] glVertexAttribPointer Problem

[Thomas <p_t...@gm...>]

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))

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

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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Re: [PyOpenGL-Users] glVertexAttribPointer Problem

[Thomas <p_t...@gm...>]

Thank you very much! Problem solved.
If you look too long at a piece of code ...

On 01/30/2011 08:27 PM, Alejandro Segovia wrote:
> 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
>>
>> ------------------------------------------------------------------------------
>> Special Offer-- Download ArcSight Logger for FREE (a $49 USD value)!
>> Finally, a world-class log management solution at an even better price-free!
>> Download using promo code Free_Logger_4_Dev2Dev. Offer expires
>> February 28th, so secure your free ArcSight Logger TODAY!
>> http://p.sf.net/sfu/arcsight-sfd2d
>> _______________________________________________
>> PyOpenGL Homepage
>> http://pyopengl.sourceforge.net
>> _______________________________________________
>> PyOpenGL-Users mailing list
>> PyO...@li...
>> https://lists.sourceforge.net/lists/listinfo/pyopengl-users