Avoid over/underflow in shader normal computation

David Gobbirequested to merge
dgobbi/vtk:avoid-shader-overflow into master

When data dimensions are very large (1e+12) or very small, the normal computations in the shader can overflow or underflow, and faces will be rendered as black. This fix scales the partial derivatives before they are used to compute the normals.

Datasets with large dimensions were correctly shaded in VTK 8.2. The incorrect rendering of this data began in VTK 9.0.0 after !6507 (merged) was merged.

Edited by Jaswant Panchumarti (Kitware)

Merge request reports