[vtkusers] How to map colors based on multiple scalars?

lovstakk lovstakk at gmail.com
Sun Dec 10 05:16:14 EST 2017

Dear VTK users, 

A relatively common use case in my field of work requires mapping
colors/alpha based on several scalars. It could for instance be based on
both velocity in addition to power or an uncertainty measure, where the
alpha value is modified using the power or uncertainty. I made this work for
images using RGB output from vtkImageMapToColors, and by appending a custom
alpha component with vtkImageAppendComponents.

My problem is that I can't seem to find out how this can be done for
polydata such as the output from vtkstreamtracer. I would like to map the
velocity scalar to color but in addition use IntegrationTime to add a
fade-in / fade-out effect using alpha-blending. I would also like to let the
velocity control some alpha to fade-out the low velocities.

Sorry if I should have gotten this from the documentation already. 

Any tips highly appreciated! 

Best regards,
Lasse Løvstakken

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