bounces = 4, so rays that have to pass 3 or 4 objects (6 or 8 surfaces) are killed early. Rendertime 5 min 40. More bounces, more rendertime - but not dramatically - less artefacts.

for the sake of it: bounces = 1 takes 1 min 20 but doesn't show any refraction effects any more (rays can enter the objects but can't leave as that would take a 2nd bounce)
and raytrace off takes 0 min 40 sec producing just 4 black boxes.

From 1 to 4 bounces adds 240 sec that's 80 sec/bounce, from 4 to 8 bounces add 180 sec = 45 sec / bounce on the avarage which is reasonable since the affected surfaces are smaller. Hence, departing from a non-raytraced scene, the extra rendertime seems just directly proportional to the amount of surface affected and directly proportional to the amount of bounces actually required.

Conclusion: when handling IDL separately (D3D script), and when surfaces are completely non-transparent, there is nothing that stops you from using high bounce values for raytracing, especially for high res / low artefact render result.

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Usually I'm wrong. But to be effective and efficient, I don't need to be correct or accurate.

visit www.aRtBeeWeb.nl (works) or Missing Manuals (tutorials & reviews) - both need an update though