POV-Ray : Documentation : Max_Intersections
  POV-Ray 3.6 Documentation Online View Max_Trace_Level Number_Of_Waves Max_Intersections

POV-Ray uses a set of internal stacks to collect ray/object intersection points. The usual maximum number of entries in these I-Stacks is 64. Complex scenes may cause these stacks to overflow. POV-Ray does not stop but it may incorrectly render your scene. When POV-Ray finishes rendering, a number of statistics are displayed. If you see I-Stack Overflows reported in the statistics you should increase the stack size. Add a global setting to your scene as follows:

 global_settings { max_intersections Integer }

If the I-Stack Overflows remain increase this value until they stop. Max_Trace_Level Number_Of_Waves

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