Triangular render errors

Support Lighting and Rendering
#1

When rendering amodel using phong shading (activating “smooth”), I allways get these triangular render errors in the area between shadow and light. Looks like the smoothing simply stops working in these areas.

phongerror.png1766×526 364 KB

I have tried to both cleanup and to triangulate the mesh, but it doesn’t help. Only workaround is to add a subdiv modifier and thus make the triangular errors so small that they don’t show up to much.
The problem appears in both the internal renderer and in Cycles.
Do I do something wrong, or is this a known issue?

#2

This is the classic terminator issue, you can resolve this by simply using a subsurf modifier.

#3

Thanks for the reply Ace Dragon. I am aware that a subdiv modifier resolves it, but putting subdiv on every model in a scene takes it its toll on rendering time. Phong shading does not cause these anomalies in other software I have used, so I guess this is a renderer error in Blender. You call it the “terminator issue” - do you know if this is something that is on the list for resolving?

#4

This is no easy fix. Most unbiased render engines suffer from this terminator artefact and only very few have found a solution so far. I wouldn’t hold my breath for a quick fix.