Tree build quality?

[RichardBlank]

I can't find info about the Tree build quality.
What is the difference between Low, Average and High?

[vlado]

This controls the algorithm which is used when building the raytrace acceleration structures; the default is "Low" in which case V-Ray uses a simple, but fairly robust algorithm that gives decent acceleration in a wide variety of scenes. The "Average" and "High" options cause V-Ray to perform more aggressive cost analysis when building the SD tree. They will generally provide faster rendering, but are somewhat experimental and not very well tested - we are still working on them.

Best regards,
Vlado

[RichardBlank]

Ok, that explains why I had problems when rendering an extremely heavy scene, 20000000 faces.
The tree build had been set to average by mistake. I switched it back to low and now it's rendering fine.
Thanks for the explanation!