[vtkusers] MIP volume rendering issue

[Jim Geach]

i'm having trouble getting sensible results from the MaximumIntensityProjection blend mode with vtkFixedPointVolumeRayCastMapper.

my data consist of two components of image data (structured points with float scalars), created like (python):

 iacRG = vtk.vtkImageAppendComponents()
 iacRG.AddInputData(colour_pts)
 iacRG.AddInputData(opacity_pts)

iacRG is the data that goes into the volume mapper. 

now, composite method works fine, but it doesn't give me the look i want -- the volume in question contains lots of buried, dense clumps surrounded by a more tenuous medium. i want to highlight these clumps whilst retaining some of that nebulosity, and i'm struggling to do this with the composite blend, as the detail gets washed out. presumably the MIP will allow these clumps to 'shine through'.

but the output from the MIP version looks really weird -- i'm seeing strange grid-like artifacts across the image, example: http://dl.dropbox.com/u/59256622/test_b_cdm_comp.png

thanks, jim