Extracting the z-buffer

OpenGL OpenGL: Basic Coding
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This is a two parter. One, I have heard there is a function to extract the z-buffer from the final image but I haven’t been able to find the function and two, does anyone know the formula for the z-buffer (I’ve been told it’s non-linear normalization to increase the accuracy of near objects)?

Thanks,
Colby

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Originally posted by Colby Toland:
does anyone know the formula for the z-buffer (I’ve been told it’s non-linear normalization to increase the accuracy of near objects)?

Hi!

You can acces the contents of Z-buffer (Depth Buffer) with glReadPixels() command. Here is a sample use :

glReadPixels( x, y, width, height, GL_DEPTH_COMPONENT, GL_UNSIGNED_BYTE, array)

… where array is a pointer to memory where depth-values (in GLubyte type in this case) will be placed.

If you’d like to know more about manipulating buffers, get your self accustomed to two other commands : glDrawPixels(), glCopyPixels().

Hope it helps!