[vtkusers] Bug in depth ordering whilst rendering

[Peter Clifton]

Hi,

I'm visualising some wave data with VTK 5.0.3, and have encountered some
strange issues with rendering.

When rotating views in some cases, some objects / surfaces always draw
on top of others, despite them being at the back of the Z-Order for the
scene.

Searching for a simple test case, I find that the "three planes" in the
example: Examples/VisualizationAlgorithms/Python/TextureThreshold.py
exhibits the symptom. I've been using Mayavi2, and the coordinate arrows
you can add into the view also exhibit the bug, at certain angles
objects at the back are drawn on top of closer objects.

In the TextureThreshold.py example, it seemed that changing the

The rendering 
 "SetOpacity(0.999)" calls to some other value, e.g. 1.5 would stop the
bug manifesting.

I've got an Intel 945GM graphics chip, and am using DRI with Mesa
7.0.1-1ubuntu3. Forcing DRI off (hence software fallback rendering in
Mesa IIRC), the rendering works fine.

Can anyone point me the the appropriate VTK Rendering code so I might
look and see which GL calls are relevant? (To go digging for what I
presume to be an underlying driver bug). I've seen a wiki entry about
depth peeling, but if I'm right, that isn't implemented in the 5.0.3
release?


Best wishes,

-- 
Peter Clifton

Electrical Engineering Division,
Engineering Department,
University of Cambridge,
9, JJ Thomson Avenue,
Cambridge
CB3 0FA

Tel: +44 (0)7729 980173 - (No signal in the lab!)