Volume Rendering : colormap is not used on the complete color range

[jzy3d]

BasicVisualizationDemo uses a ColorMapRainbow.

It appears to be used on only 2/3 of the color space :

This occurs on

• Ubuntu 20 + Dell Optiflex (Intel Iris) GPU + Intel CPU
• macOS 11.4 + Silicon CPU/GPU

This does not occur on

• macOS 10.12. + Intel CPU + NVidia GPU

[jzy3d]

May relate to

• #221
• #219