Adaptive Sampling

[atoyuser1]

Hi,

I'm trying to reduce render times with the Adaptive Sampler, but not getting many positive results

I have a bunch of semi-opaque emissive planes, with a lot of motion blur and depth of field turned on. There are no lights or HDRIs in the scene.

Here is a 512 samples render which took 15 secs:

512 samples - no adaptive sampling - 15 secs render time

Here is the same render with adaptive sampling turned on (128 min samples):

512 samples - 128 min adaptive sampling - 14 secs render time

It knocks off 1 seconds, but the quality isn't great. I tried to reduce further the min samples but that left black spots and didn't help render time:

512 samples - 64 min adaptive sampling - 14 secs render time

Any ideas how I can use Adaptive Sampling properly on this? Or perhaps I'm thinking this project isn't suitable for AS.

Thanks

[frankmci]

Try watching the Noise channel as your frame renders. I'm looking at one of your images in photoshop with the levels cranked up, and I can see that there are glow or blur gradients covering pretty much every pixel in the image, even though it looks like there are large areas of simple blackness. If those areas really were just black, you would probably see a significant reduction in render time with adaptive sampling. To reduce your render times, you're probably going to need to increase your noise threshold a bit, or reduce that glow/blur. When you watch the Noise channel, the areas that turn green have reached your threshold, and are no longer using up render horsepower.

[atoyuser1]

Try watching the Noise channel as your frame renders. I'm looking at one of your images in photoshop with the levels cranked up, and I can see that there are glow or blur gradients covering pretty much every pixel in the image, even though it looks like there are large areas of simple blackness. If those areas really were just black, you would probably see a significant reduction in render time with adaptive sampling. To reduce your render times, you're probably going to need to increase your noise threshold a bit, or reduce that glow/blur. When you watch the Noise channel, the areas that turn green have reached your threshold, and are no longer using up render horsepower.

Ah yes, sorry I forgot to mention that bloom on there.

That makes sense, I understand a bit more now. It's like saving a gif, you'll get better results with flatter colours.

Thanks for your help!

[boxfx]

You've only told us 1 of the adaptive settings what about the others?

As a basic guide:
Noise threshold: This is the overall quality of the final render and is pretty much the most important one. Use values of around 0.05 to 0.1 - A value of 0.1 will give a generally ok level of noise, I tend to lower this down to 0.08 when I need a higher quality. 0.05 is the lowest I've ever needed to push it on any project.

Min samples: This pretty much attacks the random black pixels you see. For a fast render without too many soft alpha/opacity channel gradients you can often get away with 32 samples. Anything with lots of gradients in material opacity channels tends to need more. Bump this up to 128 or 256 as needed. 512 should be about the max this ever needs to be. 64 or 128 seems to be the sweet spot.

Expected exposure: If the missing pixels tend to be in only the bright areas or dark areas, try pushing this up or down.

Group pixels: 4x4 almost always gives the best quality and render time. No idea what it really does but that's my experience.

[atoyuser1]

You've only told us 1 of the adaptive settings what about the others?

As a basic guide:
Noise threshold: This is the overall quality of the final render and is pretty much the most important one. Use values of around 0.05 to 0.1 - A value of 0.1 will give a generally ok level of noise, I tend to lower this down to 0.08 when I need a higher quality. 0.05 is the lowest I've ever needed to push it on any project.

Min samples: This pretty much attacks the random black pixels you see. For a fast render without too many soft alpha/opacity channel gradients you can often get away with 32 samples. Anything with lots of gradients in material opacity channels tends to need more. Bump this up to 128 or 256 as needed. 512 should be about the max this ever needs to be. 64 or 128 seems to be the sweet spot.

Expected exposure: If the missing pixels tend to be in only the bright areas or dark areas, try pushing this up or down.

Group pixels: 4x4 almost always gives the best quality and render time. No idea what it really does but that's my experience.

Hi, thanks for this extra info.

The Noise Threshold is 0.03. This is the default, and after a bit of googling I found the census was not many people change this.

Min samples, good to know 64-128 is the sweet spot!

Expected Exposure: 1. I was informed this only needed to match the exposure of the Camera Imager Exposure. I'll have a play

Group pixels was 2x2. I tried 4x4, but it was significantly slower. To the point where it was more efficient to up the overall samples instead

Thanks again