[vtkusers] Can you assign color to pixels in a MIP rendering?

[Mark Wyszomierski]

Hello,

I was able to do a MIP rendering of a volume using
vtkVolumeRayCastMIPFunction. This worked excellently. What I would
like to do now is assign a colored MIP scheme. If I have a colored
image say of some greyscales, as well as some pixels that are orange
and some that are blue, I would like the MIP renderer to take the
following order of precedence:

Orange pixels, blue pixels, normal greyscale intensity range thereafter.

My question is, do I have to modify anything in the
vtkVolumeRayCastMIPFunction to achieve this, or can I assign an index
to my orange pixels say of 257, and my blue pixels say 256. Then the
MIP renderer will always put those pixels above my greys (ranged 0 -
255)? I thought I could use a color transfer function to then color
pixels with index 256 blue and 257 orange, but I have been getting
unexpected results. Is this the right way to approach the problem?