What is Reddit's opinion of Mitsuba?

From 3.5 billion Reddit comments

Same tech, more optimizations, more 'cool' stuff (SSS, hair, importance/radiosity lighting), GPU-accelerated engines slowly gaining traction in the field (after games, as usual)

most raytracers have gone from linear reasoning to physically based maths (correct lighting & exposure with quadratic energy falloff, BSDFs instead of run-of-the-mill Lamberts etc...) and there's a fight between non-biased renderers (physically "correct" but slow) and plausible/biased renders (incorrect but way faster as of 2012, for the needs of 2k vfx)

I'm not a rendering expert but that's how I feel about it. If you're not using mentalray, it's incredibly easy for a beginner to make realistic images. Taste is another matter.

As for open source, I know there's Cycles with blender, but by far my favorite toy is Mitsuba: http://www.mitsuba-renderer.org/ most of cool kids in the siggraph presentations that look good have used Mitsuba.

Nobody has said Mitsuba yet? It's a reseach-grade GNU physically-based renderer. A lot new rendering algorithms are implemented there because it provides a robust/easy comparison to the state-of-the-art.

For me there is no better place for physically based rendering theory than "Physically Based Rendering: From Theory To Implementation" http://www.pbrt.org/. It is the best book about any kind of rendering I have ever read. Authors of the book have also been recently awarded an Academy Award for Technical Achievement. It has also a very good implementation from which everyone can draw.

I would recommend the book for any one. When it comes to implementation I tend to prefer http://www.mitsuba-renderer.org/. It's also based on pbrt, but the code seems much nicer (even if sometimes a bit too complex).

Mitsuba is a research renderer that should have all the features you're looking for.

Check out the paper for more info.