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Senilix

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Message 14489 - Posted: 30 May 2016, 14:55:39 UTC

Ok I have to ask...

Does the rendering really need 9 GB of RAM?
I mean, the resolution is very low (222x350) - that's why I'm asking.

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Message 14492 - Posted: 30 May 2016, 19:16:37 UTC
Last modified: 30 May 2016, 19:24:28 UTC

The memory use is seldomly directly related to the output resolution. Think about it like this: If you are rendering a very complex house with lots of little details in it, windows, colours etc. then storing all that information is what takes up a lot of space and it has to be loaded into memory to be able to use it to generate the results. The final image is a tiny tiny percentage of the size of all the models, lookup tables and so on that the rendering engine has to keep track of during the render, so it doesn't really matter much (for memory) whether you render in 10x10 or 1000x1000. The total amount of time spent rendering, however, is a completely different story because a lot of the process of rendering computes the results for each pixel in the final image.

If you go for really huge resolutions like above 10000x10000 then the so called framebuffer memory where the final image is stored will start to matter more, because the final image itself will take up a proportionally larger fraction of the total memory used.

As an example of different sizes of output and memory used for the framebuffer:
1920x1080 "full HD" (RGB ) 6.2MB
3840x2140 "4K/QFHD" (RGBA) 33.2MB
10000x10000 (32bpc float RGBA) 1600MB
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Message 14493 - Posted: 30 May 2016, 19:25:00 UTC - in response to Message 14492.  

Very well explained. Thank you for your profound answer!

A pity I can't use my 8GB machines on this one...

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Message 14494 - Posted: 30 May 2016, 19:45:15 UTC
Last modified: 30 May 2016, 20:25:25 UTC

@caetano:
There is actually a little trick to BURP and decreasing noise in renders without sacrificing speed. Rendering a small 222x350 in 3 parts and rendering a 2220x3500 in 60 parts takes about the same amount of time because many more machines get to participate. You can render big and then use bilinear rescaling to scale down the image to your intended resolution with much less noise in it.
Of course this only works if there are 60 machines ready to render - which depends on the memory amount used - for the kind of scenes you are making here you could use reduced models (decimate modifier + apply modifier, or simply less subsurf modifier) to reduce memory use while rendering only the mist.

The higher the resolution, the higher the split setting you can use. Max split if your frame is of even height is the highest number where WIDTH/#split is a whole number >32.
222pixels / 6parts = 37 pixels/part
2220pixels / 60parts = 37 pixels/part
10000pixels / 250parts = 40 pixels/part (slightly slower per-part speed, but many more machines rendering)
...
If you make it so that each part (regardless of number of parts) is around 2-3 hours of rendering then you get the optimal rendering speed.

BURP automatically does the part stitching for you before returning the full frames.
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Message 14497 - Posted: 31 May 2016, 11:03:40 UTC - in response to Message 14494.  

Thanks for this advice. I'll take it in account.
The reason I'm splitting the camera myself is because I also use Sheep it for this project, and Sheep it doesn't allow you to split animations in more than 4.
I then use Contact Sheets to combine them back.
And since I didn't think it would make a difference, I sent it as is to BURP.

But you're right, I should send it with a full frame and split it directly in BURP and also use a higher resolution.

I'm not so confident about decimating though, because the final result is pretty sharp and noiseless, and when I put it on top of the textured scene, the boundaries of the objects have to match, otherwise the transparency of the mist won't follow the edges. I could reduce the polycount inside these boundaries but that would be quite complicate and long to do.
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Message 14499 - Posted: 31 May 2016, 16:55:17 UTC - in response to Message 14497.  

Interesting point about the decimation - for some reason I was thinking that you were making some kind of "mist map" or layer and that you would do the z-testing later, but since the mist is volumetric that is obviously not how it works; the z-testing has to be done right away while actually rendering it.
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