Re: [PyOpenGL-Users] constructing a VBO containing mixture of floats, ubytes, etc

[Stephen H. <sho...@us...>]

hm well I guess theres the stride thing, and the type specifier when you use
vertexAttributes. This is off topic, but ts there any way to reply to my own
thread. I posted earlier about transformFeedback. I had to update my
graphics card drivers from opengl 2.1 to opengl 3.3 and then reinstall
pyopengl and it finally worked. Is the documentation for pyopengl going to
be updated to include the newer api functons like glBeginTransformFeedback
or glGenFrameBuffers?

On Thu, Feb 3, 2011 at 12:38 PM, Stephen Hopkins <sho...@us...> wrote:

> And the Z array you posted could be passed as a single vertex attrib
> pointer?
>
>
> On Thu, Feb 3, 2011 at 10:23 AM, Nicolas Rougier <Nic...@in...
> > wrote:
>
>>
>> Yes you can (see numpy record arrays)
>>
>> Z = numpy.zeros(100,
>>        dtype = [('position','f4',3)), ('normal','f4',3),
>> ('color','uint8',4)] )
>>
>> (see  example posted previously).
>>
>> Nicolas
>>
>>
>> On Feb 3, 2011, at 6:49 PM, Stephen Hopkins wrote:
>>
>> I dont think its possible to have 2 different data types in the same
>> array. IF you've been using Numpy, each array has a type like float32,
>>
>> zeros(3 * numVertices + 4 * numVertices , dtype=float32)
>>
>> you could make 2 vbos and bind 2 vertexAttribPointers
>>
>> colorVBO = zeros(4 * numVertices, dtype="whatever is unsigned byte")
>> vertexVBO = zeros(3*numVertices, dtype="float32")
>>
>> On Thu, Feb 3, 2011 at 3:49 AM, Jonathan Hartley <ta...@ta...>wrote:
>>
>>> Hey,
>>>
>>> I am using vbo.VBO, constructed using a single array of (position,
>>> color, normal) - all floats. This looks like:
>>>
>>>         self.vbo = vbo.VBO( array( list(
>>>                     list(chain(v, c, n))
>>>                     for v, c, n in zip(verts, colors, normals)
>>>                 ),
>>>                 'f'
>>>             ),
>>>             usage='GL_STATIC_DRAW'
>>>         )
>>>
>>> where verts, colors, normals are each generator expressions containing
>>> named tuples of (x, y, z) or (r, g, b), etc.
>>>
>>> My problem is that I want to try out converting the colors to unsigned
>>> bytes instead of floats. When I was using vertex arrays instead of VBOs,
>>> using unsigned bytes gave me something like 25% better framerates on my
>>> hardware (2004 era laptop with ATI), purely from increased rendering
>>> speeds.
>>>
>>> Does it sound likely that I'll see this sort of improvement on other
>>> hardware too? Or should I just stick with using colors as floats
>>> throughout?
>>>
>>> If I do go ahead, I'm not certain how to construct the vbo containing
>>> mixed types like this. Is there anything in OpenGL.arrays that might
>>> help, or do I need to brush up on my ctypes-fu to construct an array of
>>> structs manually?
>>>
>>> I'm happy that I do understand how to assign the vertex attribute
>>> pointers once the vbo is constructed.
>>>
>>>     Jonathan
>>>
>>> --
>>> Jonathan Hartley      Made of meat.      http://tartley.com
>>> ta...@ta...   +44 7737 062 225   twitter/skype: tartley
>>>
>>>
>>>
>>>
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>>
>>
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>