render coming out black and pixelated

[heolson]

Hey there!
Some of the shots I'm working on are turning out black in places and pixelated around the edges, while other ones with the exact same settings are turning out just fine. Certain objects seem to be rendering while others are fine. See pictures below.

I'm working in maya 13 with a series of VRay rect lights and some IES lights, using VRay physical sun and sky for the exterior lighting source. We have GI turned on, as well as caustics. The GI is set to irradiance map for the primary bounces (with preset High Animation) with light cache for the secondary. We're also rendering with a VRay physical camera with an F-number of 16 and ISO to 500.
I've also turned up my Dynamic Memory Limit to 14500, (16GB ram on computer).

We're rendering at 480x200 for testing purposes and still getting this issue.

As for project setup, we have a background scene with referenced-in props and furniture, into which we are referencing our animation.

If there's anything else you want to know that would be of use, let me know!
Thanks!

[Subburb]

Hello, i'm max user, but you should try to set on/off the subpixelmapping to see if it's better

[heolson]

Hey Subburb, I tried that just now and the render came out nearly identical with it turned on (whereas it had been off before). There are just a few less white pixels, but otherwise, still large sections of inexplicable black and the parts that had worked do look a little less grainy, so I suppose that's good. Thank you, though, and I'd be glad to hear any other thoughts you may have.

[Morbid Angel]

I think you have too many lights there which is causing the issue. My first guess would be the use of caustics and ies lights. Disable those and see if that helps. Typically such white pixels means there is a bright source in the scene but there is not enough samples to properly trace it. I would turn off everything and work my way forward turning each light one by one until you see the offending one.

[Subburb]

+1 !
and why not trying an override to see if the issue does not come from a material.
But i agree with Dmitry, test lights one by one !

[heolson]

Thank you both so much. We messed around a bit and got rid of a lot of our lights, running it almost entirely off GI at this point. We eliminated all our Vray Rect lights and just left in the IES lights and Physical sun and sky and then bumped up the samples like you suggested and it worked. Still tweaks to go to get the lighting right, but at least we've got a starting point now! Here's a screenshot of one of the shots that's now working! We also bumped up both our min and max subdivs under Adaptive DMC. Thanks again!

[Subburb]

Cool !
Honestly, thanks to Morbid Angel

[Morbid Angel]

btw are you using gi for interior and your character? be aware that your gi will flicker when that character starts to move.

[heolson]

Hey Morbid Angel, thanks for the heads up. We are using GI for the entire scene, characters included. We'll be adding some shot-specific lighting , like a rectangle light or two and working from there. If we have our Irradiance map Interp frames set to 4 or so will that reduce the flickering? Currently it's on 2, but we've only been doing test stills. If that won't help, would you suggest light linking to light the characters with something other than the Vray Sun and Sky's ambient light? I can see how that might help for a main character, but we have crowds at various points with lots of background characters moving, running even. Any suggestions?

[Morbid Angel]

Well you are coming up against a fundamental problem which is going to hit you hard once you start rendering sequences. For each animation, you will have to run a pre calculation of the irradiance map in animation mode, then run the render in irradiance mode render. The problem with this method is, if you get animation caches (or new animations) daily then repeating this process is tedious task.

I would concentrate on rendering the environment (room) or whatever it is using irradiance map/light cache using conventional methods and then rendering the characters using brute force. There is no real limitation how far you can take this, for example we've done some setups where we would create a cg environment and then render it into spherical HDR and use that in the dome light to light the moving characters in that environment (thus avoiding to multi bounce gi in the real environment). Or you can just simply render using brute force.

As example, lets say you choose going the irradiance map way, say you have to run irradiance map cache and it takes an hour. Then you need to run the render, which takes another hour. 2 hours, plus manual labor. Or you just turn on brute force and let it render for 3-4 hours. *Not saying this is the actual time relationship of course but as a simple idea.

The ultimate question here is, what would you (can you) afford to do, wait longer for brute force render, or spend the time to render irradiance maps per frame for every new animation you get.