I am trying to render a displacement map in renderman. The artifact is shown by the black patches.
This doesn't happen in mental ray; it doesn't happen with regular lights using Renderman's deep shadows (but does with regular shadows). It always happens when using an environment light (it doesn't appear to have a deep shadows setting which I thought may resolve the issues).
All that is happening in the map on these areas is that they are sunken in a little further than the rest (it's supposed to be an uneven surface), though the displacement is still not extreme.
Any help much appreciated.
The map was created in zbrush an is a 32 bit tiff.