Troubleshoot translucence limitation with raytraced shadows

User Guide > Rendering and Render Setup > Lighting > Basics of Lighting > Troubleshoot shadows >

When using raytraced shadows on a translucent object, the Translucence Depth parameter will not function correctly unless the object's transparency is non-zero. If the transparency is zero, no light will ever penetrate through the object, regardless of the Translucence Depth value.

Workaround: Adding a tiny amount of transparency to the translucent object will cause all translucence parameters to behave as expected.