Re: Getting a specific texel's intensity value

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Angus Dorbie (dorbie++at++sgi.com)
Wed, 17 Feb 1999 18:17:26 -0800

Do you want pixel or texel intensity. Unless you have a GL_REPLACE
texture environment reading a pixel using glReadPixels will not work.
You'd have to intersect and query texture coordinates then interpolate
using vertex coordinates and isect position result. That would give you
s & t which you could then use to interrogate a host based copy of the
texture image to get texel color.

All told it's a fairly involved process unless you are happy with
glReadPixels.

Cheers,Angus.

Wear, Mark wrote:
>
> Hey,
>
> Does anyone know how I might obtain a specific pixel (texel) intensity
> value from a Performer application, knowing its screen location? (example--
> Use the mouse to select a particular pixel on the screen and then return its
> intensity.) I'm using cliptextures if that is relevant.
>
> Thanks,
> Mark
> > l
> Mark E. Wear
> Electronic Systems Engineer: Real-Time Simulation
> Lockheed Martin Vought Systems
> (972) 603-2758
> mark.wear++at++lmco.com
> =======================================================================
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-- 
"Only the mediocre are always at their best." -- Jean Giraudoux


For advanced 3D graphics Performer + OpenGL based examples and tutors:
http://www.dorbie.com/

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