[a_e_k]

I sit next to Per at work. :-)

Blocks of primary rays tend to be about 16x16 by default, though this is tunable. MIP maps do greatly help with textures for incoherent rays. But we are also able to use the same trick for geometry; secondary rays may use coarser tesselations than primary rays. Per wrote about this some time ago, but it's something we still leverage. [0]

The number of bounces we do is fairly flexible. [1] We actually default to an upper limit of 10 total rays per path, with an initial limit of 1 diffuse bounce and 2 specular bounces. Depending on the geometry that's hit these initial limits may get extended until the total hits the upper limit. There are cases where the higher limits make a noticeable difference to the look.

[0] https://graphics.pixar.com/library/RayTracingCars/paper.pdf, section 5.3

[1] https://rmanwiki.pixar.com/display/REN/Trace+Depth