glossy noise with object lights?

[Buck]

For a particular scene, I have been using an object light (a large somewhat thin torus) to give almost a "ring flash" effect, only with a very large ring. The large ring is also being used for reflections.

Anyway I have been getting quite a bit of noise in the reflections on my glossy materials. I have their glossy subdivs turned to 20, and even bumped the QMC multiplier to 3.0, and still got noise. If I pump the QMC multiplier up to 6 then the image start to smooth out to a decent level. at +10, the Noise is pretty smooth and acceptable. Noise threshhold at .005, .004 or .003, doesn't seem to make any difference. QMC image sampler set at 1, 4 (will set it to 1,6 or even 1,8 for final renders)

I countered this by making the glossy subdivs at around 100+ and then bring down the QMC multiplier back to 1.0, and the level of noise is back down to a good spot. Is this normal to have 100+ subdivs on glossy materials with object light/reflections? Glossiness is from .6 to .9, and everywhere inbetween, just about everything is glossy.


Is this normal to have the glossy subdivs this high when using an object light? There is no noise in the shadows (using "low" Iradiance map, and default Lightcache settings), the noise is only on the objects reflections as far as I can tell.


If this is not normal, then I can upload a quick test scene.


Thanks!

[s0real]

have you tried using interpolation?

[Buck]

yes I have, but the results come out a bit.... odd looking. I can't describe it really, they just look a little blobby and maybe *too* smooth? I just prefer the look of them not interpolated I guess, even when the settings are high.

[s0real]

can you post any pics? (with and without interpolation)

it's usually easier to sort out when there's something to look at.

[flipside]

How did you make it self illuminated?

You probably have very strong multiplier for it, which causes problems to smooth out blurry reflections. Here's a small test. The left reflection comes from a box with a vraylightmtl on it. The right one is a box with a std material with 100 self illumination, and output map in diffuse with rgb level as light multiplier adjustment. The top one is a vray light. The red one is a box with std mtl with only 100 for self illumination. This last one is constant over the 3 images.

I changed the multipliers over each render, without touching the glossy material settings. You can see that the stronger the multiplier, the more noise, and higher rendertimes.

Maybe use lower multiplier for your object light, and then set the GI send value higher to compensate for the light loss. Reflections will look less strong of course but probably still strong enough.

Note that the vraylight reflection seems to have less problems to stay smooth.

[Buck]

yes, you are correct. I have a thin torus with a very high multiplier on the Vray light material, multilplier of 60 I believe. So, maybe I should just make a ring of visible Vray lights?

This is the render I'm working on, camera is facing straight down with the "ring light" around the camera, right light is just a tad bit larger than the car. This was with the glossy material subdivs set at 100, I'll re-render with different settings to show the difference when I get home tonight. THe renders with 30 dubdivs on the glossy materials looked horrible, looked like a very high ISO B&W photograph.

As you can see, there is still noise in the frame rails and in the carburetors, but everything else is looking good. This will be rendered kind of large, large enough to be printed 16x11, so the noise must go, or get down to at least a decent level. I'll try some more interpolation renders tonight, and maybe do some full-res crop renders to see how it holds up at larger res.
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But from the side view, I can get away with only 30 dubdivs on the metal texture when I'm using a VRay light. Some of the noise on the door and side of the car is from the maps I'm using for a "brushed metal look", which might be hiding some of the reflection noise. Is there a reason for this? Is this a bug maybe? Or is it just the nature of geometry lights? I have already done some full-res crop renders of the side shot, the metal holds up just fine.

[flipside]

The reason is the high multiplier on your torus. Your side view uses a vraylight with probably much lower multiplier.

Very strong reflections are simply harder to smooth out, I think that is normal, don't know why but it sounds reasonable

[Buck]

The reason is the high multiplier on your torus. Your side view uses a vraylight with probably much lower multiplier.

Very strong reflections are simply harder to smooth out, I think that is normal, don't know why but it sounds reasonable

thanks I'll try some more interpolation render tonight, and if they don't look good, I'll just have to render the large version over night