Re: [PyOpenGL-Users] glReadPixels wrong values

[<il...@ya...>]

Hi Pete,

This is the call I use.

b = glReadPixels(0, 0, 640, 480, GL_RGB,
GL_UNSIGNED_BYTE)

Seems to work ok for me.

If you send me an example/test of the call failing
I'll try and fix it for you.  

Otherwise try out the function above, I know that one
works :)  If you need it I could send you the code
where I use it.

Good luck!


 --- pa...@cs... wrote: > I'm trying to assign
a unique color to polygons
> drawn in one of the
> OpenGL buffers in order to do picking operations.
> When I try to read the
> colors back, I get invalid results.
> 
> I am setting the colors of each polygon in a loop
> with a command like
> the following:
> 
> glColor3us(oid, 0, 0)
> (oid increases by 1 each time through the loop)
> 
> Later, I try to read back the color of the polygon
> under the mouse
> cursor with a read pixels command like the
> following: 
> 
> pixel =  glReadPixelsus(xWX, yWX, 1, 1, GL_RED)
> 
> When I print out pixel, though, only get vales that
> seem to increase by
> 257 each time. For instance, a bunch of polygons
> will have values of 0,
> some more will have values of 257, and others will
> have values of 514.
> 
> I have made sure that the polygons are only being
> flat shaded and that
> nothing else in the pipeline is affecting their
> color values.
> 
> Can someone point out what I'm doing wrong? I have a
> feeling that it
> could be something with the multiplier values given
> in the Python OpenGL
> documentation, but I have a very vague idea of what
> they're saying.
> 
> Any suggestions will be greatly apprectiated.
> 
> Thanks,
> Pete
> 
> 

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