[vtkusers] efficiency

[Jim Morash]

> I am sure that better performance can be obtained if you 
> know in advance that you won't do shading / gradient opacity

Yes, that does make a difference (already had that turned off).

> you know that your volume is a power of two

Not sure I understand what effect this has.

> you are willing to store 3 copies of your volume in RGBA

I don't know what this means, but perhaps it relates to a mysterious
problem I'm having where the generated image is in color (mostly purple
and green) despite that I'm feeding it a single greyscale opacity
vector. (ie, I would like the final image to be in greyscale - so in a
way, all I need is the alpha channel to vary the opacity of something
that is otherwise unshaded (ie, flat grey/white)). The end result is
supposed to look like an x-ray image.

> you know the "right" settings for your card to make it work well,
I'll need to look into this part, I think.

thanks for your help.
--Jim
jmorash at mit.edu