[vtkusers] Textured IcicleView & Hardware Selector

[Eric E. Monson]

Hello,

Last week I worked up a modified version of the Icicle View which displays a texture image over the polygons. I thought I was doing something wrong because selections would sometimes highlight the correct tree elements, and sometimes not, in a seemingly random way, and depending on the texture image I used.

After a week of bashing my head against it, I finally figured out that since the vtkRenderView classes use the hardware selector I was getting unreliable results when the image I was using as a texture was too dark. As long as I have at least a small band of white all around the perimeter of my image the selector returns the correct cell IDs, and if not, then I get unpredictable results. 

Is this the expected behavior? The doxygen for vtkHardwareSelector mentions invalid results when using anti-aliasing, but should it also mention potential problems with textured PolyData? Or, is there something I could do to get reliable results with textured polydata? I'm too ignorant of the OpenGL inner workings to understand why this is happening or how to get around it.

Thanks for the help,
-Eric

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Eric E Monson
Duke Visualization Technology Group