[vtkusers] performance of MIP mappers

[Michael Knopke]

Hi Mark,

yes the mapper is resizing to max 256x256x256 for 1 component (I think it's
not 128x256x256 as stated in the API doc). Anyway in both cases this is true
if the ZDimension of the volume exceeds 256(128), otherwise it uses less
planes. SampleDistance is fixed when not moving (to the value you have
chosen), but will change to another fixed value while interacting. This
fixed interactive value is calculated once depending on the size of the
volume (so it's different with every volume you load). You can find this
calculation in vtkVolumeMapper quite at the end.

I think the only way (as a workaround of course) would be a function that
shifts opacity depending on the number of planes.

 

Regards
Michael

PS: I tried to find a general shift value myself but came to the above
conclusion, it might be wrong though.

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