prman

PRMan 17's a fairly good raytracer now (Arnold was giving PRMan a bit of a kicking in this department over the last two years).

Generally the big studios will connect Katana to PRMan or Arnold to do the heavy lifting at render time.

PRMan, MentalRay and pretty much every other renderer in day-to-day use on film and video post-production are written in C++.

Arnold and PRMan both have deferred shading which means for GI they can re-order texture requests for similar texture mipmap levels to reduce the swapping of textures needed.

For PRMan 13 (which Pixar used for Cars in 2006), they added semi-decent acceleration structures which sped up raytracing a bit.

It's been possible to write raytraced shaders in PRMan for over 12 years now.

PRMan 19 looks like it's going to fix these issues to some degree.

I believe it was used for a number of Hollywood productions alongside PRMan, since it could raytrace and do global illumination.

Once by far the dominant renderer in VFX, Arnold has come along and knocked PRMan off its perch (although Arnold still has a few issues as well).

They're using uni-directional path tracing - if they're using PRMan 17 (Which I think they were), it'll probably be unbiased like with Arnold.

Disney does not use PRman at all anymore.

DNeg are still using Mantra (and Clarisse) for a fair amount of stuff (Ant-man is their first production using just RIS in PRMan 19/20), Framestore are solidly Arnold now, and Weta are using their own PRMan clone (but a path-tracer) called Manuka.

Looks like ILM are being "coerced" into using PRMan again from what I hear...

Slight correction: his sci-tech award was for MIS and "efficient Monte Carlo path tracing for image synthesis", which have only been in PRMan for the last two releases (PRMan 18 added geo area lights with MIS evaluation, and 19 added pure path-tracing), so his award wasn't for his work at Pixar really as that happened 12+ years before the techniques the award was for made it into PRMan.