An acos() getting a negative value caused 'ray trace shadow bias' to go wrong (and object render entirely black). Only in very rare cases... but nevertheless a nice discovery fixing other unpredictable issues. (Symptom: entire object renders black)
An acos() getting a negative value caused 'ray trace shadow bias' to go wrong (and object render entirely black). Only in very rare cases... but nevertheless a nice discovery fixing other unpredictable issues. (Symptom: entire object renders black)