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Author Topic: Network render of animation causing "flickering"; omitting ambient shadow?  (Read 1203 times)
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LetItGrow
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« on: May 29, 2015, 09:42:59 AM »

Hi all, just wanted to describe a very minor issue I've had with network rendering of animations. I have four computers that I use simultaneously to render huge anims over my home network, each varying markedly in processor speed, core number, thread count, other attributes etc. The issue that I have encountered with my last animation (a high-res 3X AA animation which took ~7 "human" days to render) is that every so often one of the computers will seemingly forget to calculate ambient shadows, leaving only the main render. Upon playback of the incomplete image sequence in VDub (I'm impatient :p) this creates an obvious 'flickering' effect which greatly detracts from the otherwise high quality of the render. Now, this is in the grand scale of Life and The Universe not that great of a problem; I simply jot down which frames need to be re-rendered by my comp with the best processor, and it will successfully render the frame to include ambient shadows, and thus the issue is removed. It is however mildly annoying, and gave me quite a scare when first witnessed, as I was 3 days deep in the render and was for a while unsure if re-rendering select frames would fix the issue, until I tested.

My questions are: Have other MB3Ders experienced this? If so, what errors (if human-caused, that is) trigger this and how can they be avoided?

My process involves simply loading the .m3a on all comps from the shared folder on which it is hosted, and rendering to the same output folder without "overwrite existing" selected. I save zbuffers too and other than changing threadcount on the individual slave computers I change no other parameters. I should also note that this rendering of frames without ambient shadows occurs sporadically and in clusters. Hundreds of frames will render perfectly fine and then all of the sudden for intervals of up to ten seconds, every 12th or so frame will be rendered without shadows and will cause the flickering. I have looked at the file creation times of culprit frames, and the pattern almost definitely indicates that it is one of two of my crappiest comps doing the improper rendering: an older desktop and a laptop having nearly equal render times per frame. Given the nearly equal render times of these two machines, I can't differentiate between the two machines with the given data--though I highly suspect the laptop to be the culprit (man I hate that thing). It would be cool if rendered frames could be marked to indicate the machine that rendered it, to track issues such as this. I know I could specify one computer to render 1-500, the next to render 501-1000, etc, but having all render to one folder and unchecking "overwrite" has proven to me to be more convenient and efficient, especially during deep zooms.

A weird situation indeed  undecided

Anyways thanks to all for any insight: I've been a lurker here for quite a while and yet the efforts of posters in the FF community have been immensely helpful in advancing my understanding of MB3D!

 A Beer Cup Cheers A Beer Cup

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Yggdrasil
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« Reply #1 on: August 05, 2015, 03:00:42 AM »

My process involves simply loading the .m3a on all comps from the shared folder on which it is hosted, and rendering to the same output folder without "overwrite existing" selected. I save zbuffers too and other than changing threadcount on the individual slave computers I change no other parameters.

Hi LetItGrow,

I would be super grateful to know exactly how you manage to pull off the network rendering that you do - how can you get the M3D copies to know which frames to output, if you start the animations from the same file without specifically setting each computer to start from a specific keyframe? Wouldn't all the M3D copies try to output the same file names more or less simultaneously?

And btw  -I hope you were able to solve your lacking shadows issue!

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LetItGrow
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« Reply #2 on: September 30, 2015, 09:00:04 PM »

Quote
Hi LetItGrow,

I would be super grateful to know exactly how you manage to pull off the network rendering that you do - how can you get the M3D copies to know which frames to output, if you start the animations from the same file without specifically setting each computer to start from a specific keyframe? Wouldn't all the M3D copies try to output the same file names more or less simultaneously?

And btw  -I hope you were able to solve your lacking shadows issue!

Hi Yggdrasil, being that this is a few months later I'm not sure if this is still relevant to you, but this is easily done by unchecking 'Overwrite Keyframes' in the animation window for each computer doing the rendering. You can direct multiple computers to output completed keyframes to a shared folder on a home network. Immediately when an instance of MB3D begins rendering a keyframe, MB3D will create a file 'placeholder' (I forget the actual name for this) with the filename of the keyframe that is currently being rendered. The other computers doing the render will see this 'placeholder' and will begin rendering the next keyframe in the sequence. This prevents the need for manually setting the frame numbers each computer is assigned to render.

My computers have varying processor capabilities, so for rendering deep zoom animations where the render time needed per frame significantly increases with zoom depth, I will set the oldest machines to render the first half or third or whatever of the animation, and the newer machines to cover the second half. For example, if I am to render a 4000 keyframe-long zoom animation, I might set the two (out of four) oldest machines to render frames 1-2000, and the other two newer computers to do 2001-4000. I still leave 'Overwrite Keyframes' unchecked here, just to keep things simple. This method works for me because I can save time by dedicating the 'weaker' processors to the lighter-duty workload of doing the earlier frames before deep zooming, whereas the more powerful processors can skip straight to the hard work of rendering the more complex frames.
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