Clipping range and glDepthRange

[John Biddiscombe]

I'm still having trouble with Clipping and decided to attempt to fix it,
but I can't find any reference to
glDepthRange
in the vtk source anywhere.

This seems odd. In Renderer.cxx the clipping ranges are clamped and set up,
and in Camera the transformation matrix is created, but nowhere are the
clipping planes set in opengl. Are they assumed to be 0,1 and the
perspective transformation matrix worked in such a way that near->0 and
far->1. this seems odd.

Changing the ranges in vtkRenderer seems to be much more sensitive than I'd
expect.
For 24bit buffer (wot I'm using) setting
range[0] = 0.01*range[1] is fine but too coarse
range[0] = 0.001*range[1] is fine
range[0] = 0.0001*range[1] is bloody awful.

but 24 bits is way way more than 0.0001, so I'm confused.

For now I'm doing 

16 bits range[0] = 0.01*range[1] 
24 bits range[0] = 0.001*range[1]
32 bits range[0] = 0.0001*range[1]

but I don't like it.

Lisa? can you explain?

John B
(I must admit the perspective transformation looks odd to me).



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