[vtkusers] vtkOpenGLVolumeTextureMapper2D too slow

[Lisa Avila]

Hello Brad,

The issue was basically that with the way the volume texture mapping is 
implemented, only a subset of the functionality could be supported with the 
texture on the hardware (since in the majority of the cases the texture is 
being re-built each time).  Only when shading is off, and no parameters 
(transfer functions, cropping bounds, etc) are changing can the texture be 
re-used. Since lighting is directionally dependent (and the light is 
generally tied to the camera) any shaded volume texture mapping requires 
recomputing the textures (since shading is done in software) each frame.

There is support for saving the textures (by setting the 
MaximumStorageSize) - but this still uses immediate mode rendering for the 
textures. This could be changed in the future to support display lists for 
saving these textures.

Lisa




At 11:11 AM 2/10/2003, Bradley Lowekamp wrote:
>Hello all,
>         I was trying to render with the volume texture mapper a medium size
>volume 256x256x256, and the performance seemed rather poor. The ray
>caster at a lower resolution actually ran faster. I poked around in the
>code for the openGL volume texture mapper and it appears that it does
>not uses Texture Objects  so it does not take advantage of any on board
>memory the card has. Why has this not been implemented? volView?
>compatibility? or is it already out there some place?
>
>thanks,
> >Brad Lowekamp
>
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