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Old 22nd May 2009, 05:21 AM   #1
Professor Moriarty
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Default LightWave - Animated radiosity - flickering problem

I'm trying to stamp out flickering in a LightWave 9.6 scene that uses interpolated Monte Carlo radiosity.

One thing I'm wondering about is whether I've got the radiosity caching set correctly. I baked scene radiosity into a cache file by clicking Bake Scene Radiosity before kicking off the actual scene animation processing run, but how can I make sure that my network render nodes are using the file when rendering the scene frames?

Here are my global illumination settings. Anything jumping out at anyone? Thanks.

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Old 22nd May 2009, 05:43 AM   #2
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are you animating your objects? You can't cache and animate, I hear people say you can cache if you're only moving the camera and your objects are staying still, but I've never found that to work either

when I animate with interpolated radiosity I find it best not to use the cahce at all, I just set my interpolation settings high enough that there's no flicker
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Old 22nd May 2009, 07:11 AM   #3
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There are two objects in the scene that are in motion and the camera is also in (slow) motion relative to the scene objects. I'll try two different things and see if either works: (1) Exclude the objects in motion from radiosity. (2) Animate w/o a cache file and higher settings (any suggestions on which settings to bump up?)

Thanks...
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Old 22nd May 2009, 10:13 AM   #4
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Number of rays from the default 48 to something higher (96 or so) and bounces to more than 1 (maybe 2-3). The resulting render times will be tremendous, especially if you have a lot of small scale detail and lots of ray traced options enabled. But the flickering should reduce noticably.
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Old 22nd May 2009, 10:28 AM   #5
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I know I get flicker in Maya when I use Final Gather and the FG ray limit is too low. If you've got that turned on, either turn it off or up the FG rays...
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Old 22nd May 2009, 11:08 AM   #6
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Quote:
Originally Posted by MayaMan View Post
I know I get flicker in Maya when I use Final Gather and the FG ray limit is too low. If you've got that turned on, either turn it off or up the FG rays...
Nope, not using final gather.

One thing I have discovered is that if I turn down the minimum pixel spacing from 4.0 to 1.0 that a lot of the blotchy artifacts disappear (which when I think about it I guess makes sense). If I turn maximum pixel spacing down to 1.0 also, doesn't that essentially turn interpolated mode off?
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Old 22nd May 2009, 12:18 PM   #7
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I'd set maximum pixel spacing to something low, and minimum to something a bit lower (I often use 1 pixel for maximum actually) and then set my rays per evaluation to something high like 192 to 300

your objects are animated so the cache will screw up, turn it off and just let it pre calculate for every frame - it should still be faster than non interpolated rad

also if you don't need the bounced rad then turn that off too, I've found the extra bounces are a huge render hit during calculation (even if you leave the secondary rays on something low like 16)
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Old 22nd May 2009, 12:54 PM   #8
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Quote:
Originally Posted by IRML View Post
I'd set maximum pixel spacing to something low, and minimum to something a bit lower (I often use 1 pixel for maximum actually) and then set my rays per evaluation to something high like 192 to 300

your objects are animated so the cache will screw up, turn it off and just let it pre calculate for every frame - it should still be faster than non interpolated rad

also if you don't need the bounced rad then turn that off too, I've found the extra bounces are a huge render hit during calculation (even if you leave the secondary rays on something low like 16)
So... something along these lines?



Won't the lack of caching cause inter-frame flickering because of differing radiosity calculations between the four CPUs in my mini-render farm, even though all four are identical CPU models?
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Old 22nd May 2009, 02:48 PM   #9
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the idea is you've set it high enough that the rad will look almost as good as non interpolated and won't flicker

there is an animated cache, but it's slower than using non interpolated rad, in fact what you do is bake the cache before the main render, and then it just seems to render like non interpolated rad after that, I have no idea what it's meant to be used for, but my guess is it's not really ready for inclusion with lightwave yet but they chucked it in anyway

your rad is calculating on a frame by frame basis so there'll be no problems, and if all your CPUs are identical then there should definately be no problems

even if your CPUs are different problems are rare anyway, stuff like the pattern of the noise in your image ends up slightly different, which you'll never notice because it's completely different between frames anyway, I think it's pretty rare that you get proper errors, maybe stuff using procedurals or expressions using random number generators will screw up with different CPUs in your farm

I can't really just look at your settings and tell you if they'll work or not, it's very scene dependent and the only way you're going to know is if you test render a few frames, one thing I notice is you turned off secondary bounce rays instead of turning off the number of bounces, and I'd probably set your maximum pixel spacing somewhere between 2 and 5, if that doesn't work then try lowering it to 1

also you have to find the right balance between your min/max pixel spacing and your rays per evaluation, so be prepared to tweak both of those
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Old 22nd May 2009, 04:04 PM   #10
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The speed of that, as IRML says is really scene dependant. Usually when I am using blurry reflections I get huge issues with speed, but I am getting better at dealing with that

I'd say make your primary rays 256 and I would leave your bounce rays to 16. You might want to lower your angular tollerance to something like 30 (depends on the scene, your setting might be right) and enable gradients, as that looks nicer (but again... you know the drill! )

The animation cache, yes, can be slower than rendering it without, just try out a few renders with it disabled. Depends on how your scene is lit, and if there's any rogue hotspots which might cause weird bounces round the scene, and flickering.

You might also want to have some shader based ambient occlusion (DO NOT use the radiosity occlusion, it's horrible, in interpolated mode) to fill some shadows, and actually here's some advice you won't hear outside of radiosity speak - turn up your ambient lighting global amount. It will help speed up and soften the radiosity. Again tweak to taste!
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Old 22nd May 2009, 05:20 PM   #11
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Personally ... I'd be looking at comping as much as you can. Bake all the BG elements that aren't moving. You can use an AO pass to fake the rad pretty well. Then do it all in post. It will allow you much more room to tweek it later. Failing that everything mentioned above will work well.
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Old 23rd May 2009, 09:16 AM   #12
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Thanks guys... this gives me a lot of things to try out when I'm back from holiday on Monday evening!
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Old 23rd May 2009, 09:24 AM   #13
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Caching works with animation, but it depends on your scene and the type of animation involved:

1. Do the objects in the scene move?
2. Do the objects in the scene deform?
3. If only the camera is moving, how fast?

If you have the patience to read through a long but very educational radiosity guide, read this.
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Old 23rd May 2009, 03:00 PM   #14
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1. yes
2. no but some parts spin/rotate
3. pretty slowly in this particular scene but not all scenes

And funny you should link to that webpage... I've been studying it for the past few days but it raised as many questions as it answers (and plus it was written for version 9.5... ambient occlusion isn't even mentioned, for example)... still, it seems to be one of the better guides I've found so far.
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Old 25th May 2009, 06:57 PM   #15
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Well, the good news is that the flickering during animation has completely vanished with the new settings which up the rays per evaluation to 256, lowers the angular tolerance to 30 degrees, and sets the minimum and maximum pixel spacing to 1.0:



The bad news is that render times have suffered horribly--the time required to calculate GI is now over 13 minutes for a single 720x480 frame... yuck!

The results are definitely worth it though--now I just need to experiment with these adjusted settings to see where the sweet spot between render time and visible flicker occurs. Thanks...
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Old 26th May 2009, 03:31 AM   #16
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Not sure what the differences are but Exception has updated his guide for 9.6 here: http://www.except.nl/lightwave/Radio...de96/index.htm
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Old 26th May 2009, 04:39 AM   #17
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Quote:
Originally Posted by SteveMoody View Post
Not sure what the differences are but Exception has updated his guide for 9.6 here: http://www.except.nl/lightwave/Radio...de96/index.htm
Awesome! Thanks for the update notification. (He also has an interesting article on the new antialiasing system that I found very helpful.)
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Old 28th May 2009, 08:34 PM   #18
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Quote:
Originally Posted by Professor Moriarty View Post
Well, the good news is that the flickering during animation has completely vanished with the new settings which up the rays per evaluation to 256, lowers the angular tolerance to 30 degrees, and sets the minimum and maximum pixel spacing to 1.0:



The bad news is that render times have suffered horribly--the time required to calculate GI is now over 13 minutes for a single 720x480 frame... yuck!

The results are definitely worth it though--now I just need to experiment with these adjusted settings to see where the sweet spot between render time and visible flicker occurs. Thanks...
You may be able to get away with 50% on the Multiplier and save lots of time, the difference is barely noticeable.
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Old 29th May 2009, 04:05 AM   #19
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put your angular tolerance back up to 45, that should speed things up

you haven't even shown us what it is you're trying to render, what toeB just said could work, but it depends on how many fine details your object has

and (if you can get away with it) don't use multiple bounces, that slows the render down the most
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