Re: [PyOpenGL-Users] glGetUniformLocation causes segmentation faults

[richard h. <rha...@cs...>]

I moved over to my desktop which has a  GeForce GTX 260, and is also
running 64 bit Ubuntu 9.04.  This machine also segfaults when I call
glGetUniformLocation.  As I expected, the enumeration of the uniform
resources changed between my Intel card and this GeForce.  The GeForce
enumerates as follows for me:

glUniform3f(0, 1.0, 0.3, 0.2)
glUniform3f(4, 0.85, 0.86, 0.84)
glUniform2f(2, 0.30, 0.15)
glUniform2f(1, 0.90, 0.85)
glUniform3f(3, 0.0, 0.0, 4.0)

Also I installed pyopengl using the python-opengl package in apt if
that might help at all.

I also added calls to glGetError, but it appears that nothing is
failing.  Below is an excerpt of my changes:

------------------------------------
...
vert = glCreateShader(GL_VERTEX_SHADER)
print "glGetError - glCreateShader: ", glGetError()
frag = glCreateShader(GL_FRAGMENT_SHADER)
print "glGetError - glCreateShader: ", glGetError()

glShaderSource(vert, self.vert_src)
print "glGetError - glShaderSource: ", glGetError()
glShaderSource(frag, self.frag_src)
print "glGetError - glShaderSource: ", glGetError()

glCompileShader(vert)
print "glGetError - glCompileShader: ", glGetError()
glCompileShader(frag)
print "glGetError - glCompileShader: ", glGetError()

program = glCreateProgram()
print "glGetError - glCreateProgram: ", glGetError()
glAttachShader(program, vert)
print "glGetError - glAttachShader: ", glGetError()
glAttachShader(program, frag)
print "glGetError - glAttachShader: ", glGetError()

glValidateProgram(program)
print "glGetError - glValidateProgram: ", glGetError()
glLinkProgram(program)
print "glGetError - glLinkProgram: ", glGetError()
glUseProgram(program)
print "glGetError - glUseProgram: ", glGetError()

# Any of the following will cause a segmentation
# fault.  (due to the call to glGetUniformLocation)
glUniform3f(self.getUniLoc(program, "BrickColor"), 1.0, 0.3, 0.2)
...
------------------------------------

which now gives me the output:
GL_VENDOR:  NVIDIA Corporation
GL_RENDERER:  GeForce GTX 260/PCI/SSE2
GL_VERSION:  3.0.0 NVIDIA 180.44
...
glGetError - glCreateShader:  0
glGetError - glCreateShader:  0
glGetError - glShaderSource:  0
glGetError - glShaderSource:  0
glGetError - glCompileShader:  0
glGetError - glCompileShader:  0
glGetError - glCreateProgram:  0
glGetError - glAttachShader:  0
glGetError - glAttachShader:  0
glGetError - glValidateProgram:  0
glGetError - glLinkProgram:  0
glGetError - glUseProgram:  0
Segmentation fault

Thanks for the help,
Richard

On Thu, Jun 25, 2009 at 10:24 AM, Mike C.
Fletcher<mcf...@vr...> wrote:
> richard hawkins wrote:
>> Hello all,
>>
>> I am having some trouble with a simple test application.  I am mixing
>> one of the nehe tutorials with the brick example from the OpenGL
>> orange book.
>>
>> Here is my problem, all calls to glGetUniformLocation result in a
>> segmentation fault.  I removed all calls to glGetUniformLocation, and
>> played around with guessing the appropriate values.  Doing this I was
>> able to get the shader to render correctly, but is not a good way to
>> do things.
>>
> Interesting, my machine bombs out (not a segfault, just an invalid
> operation) when trying to do glUseProgram.  I'd suspect that something
> is failing during compilation and you just aren't retrieving a
> compilation error message to see the failure?  Don't have time to track
> it down this morning (already late for meeting).  (Tested on an Ubuntu
> 9.04 64-bit with AMD Radeon, btw).
>
> Good luck,
> Mike
>
> --
> ________________________________________________
>  Mike C. Fletcher
>  Designer, VR Plumber, Coder
>  http://www.vrplumber.com
>  http://blog.vrplumber.com
>
>



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