It has been a few months since the release of 2.78, and the Blender Foundation has been sitting on a bunch of performance enhancements in that time. Since 2.79 is still a couple of months off, they decided to “cherry pick” a bunch of them back into the 2.78 branch and push out an update to it. Most of these updates are things like multi-threading their shader compiler for Cycles, speeding up motion blur in Cycles, and reducing “fireflies” in Cycles renders, which indirectly helps performance by requiring less light samples to average out the noise.
I tried running two frames from different scenes of my upcoming PC enthusiast explanation video. While they’re fairly light, motion graphics sequences, they both use a little bit of motion blur (~half of a 60 Hz frame of integration) and one of the two frames is in the middle of three objects with volumetric absorption that are moving quite fast.
The "easier" scene to render.
When disabling my GTX 670, and only using my GTX 1080, the easier scene went from 9.96s in 2.78a to 9.99s in 2.78b. The harsher scene, with volumetric absorption and a big streak of motion blur, went from 36.4s in 2.78a to 36.31s in 2.78b. My typical render settings include a fairly high sample count, though, so it’s possible that I could get away with less and save time that way.
The "harsher" scene to render.
Blender is currently working on Agent 327, which is an upcoming animated feature film. Typically, these movies guide development of the project, so it makes sense that my little one-person motion graphics won’t have the complexity to show the huge optimizations that they’re targeting. Also, I had a lot of other programs running, which is known to make a significant difference in render time, although they were doing the same things between runs. No browser tabs were opened or closed, the same videos were running on other monitors while 2.78a and 2.78b were working, etc. But yeah, it's not a bulletproof benchmark by any means.
Also, some of the optimizations solve bugs with Intel’s CPU implementation as well as increase the use of SSE 4.1+ and AVX2. Unfortunately for AMD, these were pushed up right before the launch of Ryzen, and Blender with Cycles has been one of their go-to benchmarks for multi-threaded performance. While this won’t hurt AMD any more than typical version-to-version variations, it should give a last-minute boost to their competitors on AMD’s home turf.
Blender 2.78b is available today, free as always, at their website.