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Old 02-13-2013, 09:36 PM   #1
Defonten
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Natiq Aghayev
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Exclamation Good old FG+Animation problem. Help

Hi,

I got a bright room lit with one mr Spot and active FG in my scene. The problem is that I have to render it to full hd 1920x1080, and while in lower resolutions it renders in more or less acceptable amount of time, but the minute I change resolution to Full hd - it takes 1+ hour to render one frame..

Also i'm experiencing jitter and noise which I obviously could avoid if I raised "Rays per FG point" to a number of 2000-3000 or higher, but in than case it takes hours and hours to calculate.. What am I doing wrong?

I know I can make a map and later read from it, and that would be cool, but creating a map isn't working for 100% also - from time to time strange ugly black spots appear here and there and I don't have any idea where they come from..

Any help would be much much appreciated!

Last edited by Defonten : 02-13-2013 at 09:40 PM.
 
Old 02-14-2013, 02:24 AM   #2
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Do you have a render you can show? You shouldn't need to go higher than 1,000 points especially at that resolution. Baking the animation, when done correctly, shouldn't have any spots showing up, but we need to make sure your render is setup correctly first. If you aren't working in a physically correct way you can end up with some weirdness.
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Old 02-14-2013, 11:37 AM   #3
Defonten
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Well, due to some legal obligations I can't but nothing super fancy - just a big white bright room with windows and fluttering curtains (curtains are excluded from FG)

It's strange, you say 1000 is often enough, but look, when I'm even on 1200 rays per FG Point I get quite blurry result which don't give the detailed look at all. 3000 is nice. But according to MR parameters HIGH settings include 10 000 points! My comp will die even before hitting that render button..
 
Old 02-14-2013, 12:40 PM   #4
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In my opinion there is no "absolute" value that can be accepted adequate with mental ray. It depends on the size,extents and the unit setup of your scene. I don't mean to dissappoint you but furthermore I assure you that even if you render with "highest" point count you'll most likely have refined but still flickering grains. When your scene size or scene units change, the adequate number of samples differ greatly.

I've been trying to solve this situation myself for ages. Starting from scratch, I keep myself from using render time increasing items, like blurred reflections, soft shadows, depth of field motion blur... There are still unacceptable flickering even if FG quality is set to highest.

I often have many questions.

I have an antic theatre model that I ve created with the DOS version of 3DS. It's a large area about 250 meters in diameter with several columns seats The scene units were metric at that time. May be about 15 years ago I converted the scene to max format.
Today this scene renders extremely fast and very good quality, compared to many other scenes of mine.

At Initial points set to 2, samples per point 100 and the 30 or 50 interpolation. It renders 1920x1080 resolution min-max samples 1-16 at 2 to 5 minutes. (i7 3930 K PC) This is the result. There is no applied ambient occlusion effect but the dark areas near the edges are amazing. (There is a barrel camera effect+round corners on most materials) No flickering in animation. I can't achieve this result easily with any other scenes of mine.



I really don't understand. It's a real problem to keep control of your scenes.

You may try the above values. Also be careful with your other material effects, area lights etc. They greatly add to render time.

On some cases, render settings are either corrupt or stuck in memory for some reason and translation time starts to take longer than before. Just like rendering never starts.
Changing the renderer (to scanline or alike) and switching back to mental ray helps. That's also confusing.
 
Old 02-14-2013, 02:20 PM   #5
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I wish it was as simple as "higher samples = better" (try Iray if this is more your style) but whats really important is learning how the settings work together. A common way to get a render quickly from MR is to use less samples, more interpolation which is quick, but will be kind of a "soft" looking solution. Then you can use AO on your materials to get some of that detail back. Simply clicking High or Very high will likely get you a super blotchy, terrible looking render and take forever. There is more to it than that. Try the Medium preset and see how that looks, but increase your interpolate over num fg points value to 60 or 100.


EDIT - Just noticed you said you are using an MR spot light. Try not to use that, use the Photometric lights instead. Also, if you are lighting a single scene with just one light, you are probably going to need GI also.
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Old 02-14-2013, 07:44 PM   #6
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Hey thanks for the advice guys! Totally agree, there's no magic button like "make everything beautiful" ) No matter how hard I was at the previous FG task, I can't gurantee that I will get the same results with the new scene.. Everytime it's a totally different experience.

I kinda solved the problem, I decided to wait for about an hour for FG map to be generated, and since there's almost no movement in my scene, I just render it with this high quality cached FG map on.
 
Old 02-14-2013, 07:44 PM   #7
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