Merge topic 'rectilinear_grid_volume'

70bdf395 Fix warning about uninitialized variable
ab053be4 Merge branch 'master' into rectilinear_grid_volume
e84139fd Use a single 1D 3-component texture for texture coords of rect grids
cfa4d75b Simplify generated shader code for rectilinear grid volume
cfd9abb8 Re-enable TestGPURayCastCropping1
0e25b991 Compute voxel bounds of cropped region for rectilinear grids
f5bb42b2 Workaround GLSL error with non-constant sampler array index
043875c8 Add test for non-linear-spaced rectilinear grid volume rendering
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Acked-by: Kitware Robot <kwrobot@kitware.com>
Acked-by: Cory Quammen <cory.quammen@kitware.com>
Merge-request: !6835