pyopengl-users

[PyOpenGL-Users] No stencil buffer?

[Jordan S. <jso...@MI...>]

I've been developing a simple application using PyOpenGL for a few weeks 
now, and trying to add a feature that requires use of the stencil 
buffer.  However, the stencil buffer doesn't seem to be working- all 
pixels pass the test, even when the test is GL_NEVER.  
glGetInteger(GL_STENCIL_BITS) returns 0, but running glxinfo on my 
machine shows that my graphics card supports an 8 bit stencil buffer.  
I'm running Ubuntu and my graphics card is an nVidia GeForce Go 7300.  
Anyone have any ideas?
Thanks a ton,
-JS

Re: [PyOpenGL-Users] No stencil buffer?

[Gary H. <gh...@is...>]

Jordan Sorensen wrote:
> I've been developing a simple application using PyOpenGL for a few weeks 
> now, and trying to add a feature that requires use of the stencil 
> buffer.  However, the stencil buffer doesn't seem to be working- all 
> pixels pass the test, even when the test is GL_NEVER.  
> glGetInteger(GL_STENCIL_BITS) returns 0, but running glxinfo on my 
> machine shows that my graphics card supports an 8 bit stencil buffer.  
> I'm running Ubuntu and my graphics card is an nVidia GeForce Go 7300.  
> Anyone have any ideas?
> Thanks a ton,
> -JS
>   

How are you creating your window?    The  window, and any
depth/stencil/aux buffers associated with it, are not created by OpenGL,
but are part of the context created with the window via what ever method
you use to create the window.  So I repeat -- what method do you use to
create a window, and can you find a way to specify a stencil buffer at
that time?

Gary Herron

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Re: [PyOpenGL-Users] No stencil buffer?

[Lorenzo M. <lma...@de...>]

Jordan Sorensen wrote:
> I've been developing a simple application using PyOpenGL for a few weeks 
> now, and trying to add a feature that requires use of the stencil 
> buffer.  However, the stencil buffer doesn't seem to be working- all 
> pixels pass the test, even when the test is GL_NEVER.  
> glGetInteger(GL_STENCIL_BITS) returns 0, but running glxinfo on my 
> machine shows that my graphics card supports an 8 bit stencil buffer.  
> I'm running Ubuntu and my graphics card is an nVidia GeForce Go 7300.  
> Anyone have any ideas?

IIRC the stencil buffer shares the available bits of the depth buffer; 
thus, the choice is between having a 24 bit depth buffer with no stencil 
buffer and a 16 bit depth buffer with 8 bit stencil buffer.

-- 
Lorenzo Mancini

Re: [PyOpenGL-Users] No stencil buffer?

[Jordan S. <jso...@MI...>]

Yep, that was it- I wasn't allocating a stencil buffer when I 
initialized GLUT.  Thanks a ton for your help!  I appreciate it.
Thanks,
-Jordan

Dirk Reiners wrote:
>
>     Hi Jordan,
>
> Jordan Sorensen wrote:
>> I've been developing a simple application using PyOpenGL for a few 
>> weeks now, and trying to add a feature that requires use of the 
>> stencil buffer.  However, the stencil buffer doesn't seem to be 
>> working- all pixels pass the test, even when the test is GL_NEVER.  
>> glGetInteger(GL_STENCIL_BITS) returns 0, but running glxinfo on my 
>> machine shows that my graphics card supports an 8 bit stencil 
>> buffer.  I'm running Ubuntu and my graphics card is an nVidia GeForce 
>> Go 7300.  Anyone have any ideas?
>
> The stencil buffer needs to be allocated when the window is created, 
> as it takes resources that not all applications need. How do you 
> create the window? If it's GLUT, the glutInitDisplayMode function 
> takes an option that allows you to specify it.
>
> Hope it helps
>
>     Dirk
>
>