[Radiance-general] clipping planes exposing object interiors?

[Carsten Bauer]

Hi,

In fact, it doesn't matter for the ambient calculation if polygons 
overlap or cut into each other, making the edge between them 'airtight'.
When reusing ambient values from the cache no 'quasi shadow testing' is 
done to ensure that nothing lies inbetween for the 'allowed' radius of 
this ambient value. Theoretically, this perhaps might be possible, but 
certainly at a very high computational cost.

So the solution is to set the ambient resolution -ar sufficiently high 
(and/or) -aa low. The size of the scene cube also plays a role as can be 
seen in the expression for rmin in Axels answer, so a big outside (e.g 
large ground polygon) increases the problem. (In the RwR book there is a 
section on this, and the use of a 'ground glow' is recommended to 
circumvent this problem.

If you want to model a huge outdoor part, it is better to use separate 
ambient caches for the 'outside' and the 'inside' part of your scene.

-cb