All that is said here is correct. Just want to point out that some of you are talking about reflection/refaction bounces and some of you are talking about diffuse bounces (for IDL).

These are not the same, and statements made about one are correct while also false about the other.

In a nutshell:

Reflections will stop when a non-reflective surface is encountered, regardless of what you set the raytrace reflection limit at. Thus - if you have no Reflect nodes in your scene, the render setting means nothing at all. If you have one object that can reflect, then the render setting may still have no meaning at all. It depends on how many times your objects try to reflect. Anthanasius set up mutually reflecting closely-spaced spheres so, the number of times it tried to reflect was very high. The limit would matter there.

Refractions follow the same rule as reflections. aRtBee showed an example - using glass lenses to see through other glass lenses. If you had only one glass lens, then after two refractions, it would stop on its own, so setting bounces = 2 or bounces = 2000 would make no diffence.

The raytrace bounces is there to HALT the reflections and refractions. Imagine a ceiling set to 8 feet, to stop me from jumping that high, only because I'm unable to jump above 7 feet, the ceiling height makes no difference. That's what you guys are talking about. However, when Michael Jordan jumps, his head hits that ceiling. Then it mattered.

 

As for IDL, it's a totally different thing. The number of bounces will nearly always be used, so it's not a limit - it's an actual setting, and with all settings that consume CPU, the higher it is, the more accurate the lighting, and also the longer it will take.

Having your IDL bounces too low will cause the simulation to fail to include some bounced light that really should be there. Having it too high will always cost you render time.

Having your reflection/refraction bounces too low may cause a reflection to disappear. Having it too high will rarely cost you render time. It will cost render time if you set up mutually infinite reflective surfaces. (Think of mirrors in the beauty salon on both sides of the room.)

 

 

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)