pyopengl-users

[PyOpenGL-Users] Attribute error using PyOpenGL and PyOpenCL

[Walter W. <hom...@gm...>]

Hello,

I came across a problem and hope that you can help me,
since I could not find a solution crawling the net.

I was trying to run some examples to visualize OpenCL
calculations using OpenGL with shared buffers using

Python 3.3
PyOpenGL 3.1.0
PyOpenGL-accelarate 3.1.0
pyopencl 2014.1

The examples are similar, one that might serve as example is
https://gitorious.org/openclgltest/openclgltest

Trying to run this throws the error:

Traceback (most recent call last):
  File ".\testpyopengl.py", line 234, in <module>
    mytest = test()
  File ".\testpyopengl.py", line 91, in __init__
    self.loadclData()
  File ".\testpyopengl.py", line 205, in loadclData
    self.arr_cl = cl.GLBuffer(self.ctx, mf.READ_WRITE,
int(self.arrvbo.buffers[0]))
  File "vbo.pyx", line 177, in OpenGL_accelerate.vbo.VBO.__
getattr__ (D:\Build\PyOpenGL\pyopengl-bzr\OpenGL_accelerate\src\vbo.c:2757)
AttributeError: 'numpy.ndarray' object has no attribute 'buffers'

Here are two things that might be related to the issue:

1.) PyOpenGL 3.1.0b3; Py_buffer on Python3 unsupported
https://sourceforge.net/p/pyopengl/mailman/message/32385909/

2.) This post that mentions that Python 3 might be the problem. Is that the
case?
http://stackoverflow.com/questions/21821045/numpy-getbuffer-causes-attributeerror-module-object-has-no-attribute-getbuff

I found that another example
https://github.com/enjalot/adventures_in_opencl/blob/master/python/part2/part2.py
was trying to fix this like

try:
    self.pos_cl = cl.GLBuffer(self.ctx, mf.READ_WRITE,
int(self.pos_vbo.buffer))
    self.col_cl = cl.GLBuffer(self.ctx, mf.READ_WRITE,
int(self.col_vbo.buffer))
except AttributeError:
    self.pos_cl = cl.GLBuffer(self.ctx, mf.READ_WRITE,
int(self.pos_vbo.buffers[0]))
    self.col_cl = cl.GLBuffer(self.ctx, mf.READ_WRITE,
int(self.col_vbo.buffers[0]))

But changing the example above like this results in

Traceback (most recent call last):
  File ".\python-3.3.3.amd64\lib\site-packages\OpenGL\GLUT\special.py",
line 130, in safeCall
    return function( *args, **named )
  File ".\testpyopengl.py", line 182, in draw
    gl.glVertexPointer(4, gl.GL_FLOAT, 0, self.arrvbo)
  File "latebind.pyx", line 32, in
OpenGL_accelerate.latebind.LateBind.__call__
(D:\Build\PyOpenGL\pyopengl-bzr\OpenGL_accelerate\src\latebind.c:992)
  File "wrapper.pyx", line 314, in
OpenGL_accelerate.wrapper.Wrapper.__call__
(D:\Build\PyOpenGL\pyopengl-bzr\OpenGL_accelerate\src\wrapper.c:6508)
  File "wrapper.pyx", line 311, in
OpenGL_accelerate.wrapper.Wrapper.__call__
(D:\Build\PyOpenGL\pyopengl-bzr\OpenGL_accelerate\src\wrapper.c:6442)
  File
".\python-3.3.3.amd64\lib\site-packages\OpenGL\platform\baseplatform.py",
line 402, in __call__
    return self( *args, **named )
ctypes.ArgumentError: ("argument 4: <class 'TypeError'>: wrong type", (4,
GL_FLOAT, 0, <OpenGL_accelerate.vbo.VBO object at 0x0000000004752A60>))
GLUT Display callback <bound method test.draw of <__main__.test object at
0x0000000003A959B0>> with (),{} failed: returning None ("argument 4: <class
'TypeError'>: wrong type", (4, GL_FLOAT, 0, <OpenGL_accelerate.vbo.VBO
object at 0x0000000004752A60>))

Well, that for now. I hope you have some ideas on how to fix this.

Kind regards,
Joe

Re: [PyOpenGL-Users] Attribute error using PyOpenGL and PyOpenCL

[Mike C. F. <mcf...@vr...>]

On 14-09-24 07:40 AM, Walter White wrote:
> Hello,
>
> I came across a problem and hope that you can help me,
> since I could not find a solution crawling the net.

Basically the code is trying to access the "buffers" member of the VBO 
object. The OpenGL_accelerate version of the VBO (the cython-implemented 
one) does *not* have a .buffers (list), only a .buffer (int). Probably 
the attributes should be named _buffer and/or _buffers, as they aren't 
normally used by external code, the normal way to get the ID of the VBO 
is int(<vbo>).

HTH,
Mike

-- 
________________________________________________
   Mike C. Fletcher
   Designer, VR Plumber, Coder
   http://www.vrplumber.com
   http://blog.vrplumber.com

Re: [PyOpenGL-Users] Attribute error using PyOpenGL and PyOpenCL

[Joe <hom...@gm...>]

Hello,

thanks for your reply.
The example is working now, I replaced the buffers entry
with int(<vbo>) as you suggested.

But after that I ran into another problem, which I found
a solution for but I don't know why it works.

Here again the link to the example:
https://gitorious.org/openclgltest/openclgltest/source/7b9969ef093e7bc04100a860588e6bb115731d97:testpyopengl.py#L173

There was a "wrong type" error in the last parameter of the
following calls:

 > 173 gl.glVertexPointer(4, gl.GL_FLOAT, 0, self.arrvbo)
 > 175 gl.glColorPointer(4, gl.GL_FLOAT, 0, self.colvbo)

I did not know what to do and changed it to "None":

 > 173 gl.glVertexPointer(4, gl.GL_FLOAT, 0, None)
 > 175 gl.glColorPointer(4, gl.GL_FLOAT, 0, None)

and that worked. But I have absolutly no idea why.
Why do the functions know where the vertices / colors
are as I do not specify a pointer to the VBO?

Has it something to do with the .bind() calls of the VBO
before glVertexPointer / glColorPointer?

 > self.arrvbo.bind()
 > gl.glVertexPointer(4, gl.GL_FLOAT, 0, self.arrvbo)

 > self.colvbo.bind()
 > gl.glColorPointer(4, gl.GL_FLOAT, 0, self.colvbo)

Kind regards,
Joe

Am 30.09.2014 21:24, schrieb Mike C. Fletcher:
> On 14-09-24 07:40 AM, Walter White wrote:
>> Hello,
>>
>> I came across a problem and hope that you can help me,
>> since I could not find a solution crawling the net.
>
> Basically the code is trying to access the "buffers" member of the VBO
> object. The OpenGL_accelerate version of the VBO (the cython-implemented
> one) does *not* have a .buffers (list), only a .buffer (int). Probably
> the attributes should be named _buffer and/or _buffers, as they aren't
> normally used by external code, the normal way to get the ID of the VBO
> is int(<vbo>).
>
> HTH,
> Mike
>