[Bf-cycles] Tiles sizes - impact on RAM and speed

[Ole Jakob Skjelten]

Hi!

I've spent quite a bit of time recently setting up a GPU hardware FAQ for Cycles, based mostly on the recurring questions from the support forum at BlenderArtist. I feel I got most of it covered, but one type of questions keeps coming up that I do not have a good answer for, and that is the impact Cycles tile sizes has on total VRAM and rendering speed. I've seen a lot of empirical testing, but it's hard to transfer this into some solid general advice.

I suppose I'm trying to answer the questions "which tile size gives optimal speed given my scene and hardware?" and "how does tile size impact VRAM requirements?" (which also answers the questions "I get an out of memory error, can I do something about that?").

I was hoping there was some sort of formula I could use to understand the relationship between tile size and VRAM usage, and the impact on number of calculations required for a full scene. I've asked around everywhere I could think of, and though people have a lot of anecdotal evidence one way or another, I've yet to get any closer to the underlying technical details. But perhaps there is someone on this list that could settle this once and for all? (I promise to distribute the answer broad and wide ;)


OJ

PS: You can find the FAQ at http://www.systemagnostic.com/faq

--
Ole Jakob Skjelten
olesk at pvv.org
+41 79 832 2976




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