Noisy Renders

[Frank21]

I played with the denoiser today after disappointing results a few months back. In one render (dark room) it worked brilliantly, changed the camera angle and zoom a bit an the next render looked totally awful. It seems denoiser is very temperamental about a lot of variables.
First render was super fast and finished in a few minutes but I would be prepared to wait longer for a less denoised one. I just wish there was a way to adjust the level of denoising rather than just on or off.

[Amber]

A few notes:
Intel Open Image Denoise is designed specifically for raytraced renders... in fact, it can tell the difference and basically ignores anything else. That's why it seems to work better on 3D renders... because it *does* :p

Gigapixel is "fair", but objectively speaking, it is very destructive to any image's detail to achieve a smooth appearance. You'd probably get better results using a gaussian blur in Photoshop FWIW. Basically, it eats photographs and shits rainbows.

On the pre-side; you know Iray *LOVES* light. make sure you feed it plenty and it will reward you with a crisp image. You can crank up the scene and environment light levels and fiddle the gamma a bit in render settings to give yourself a hot proof, you should then give it a cool bath in Photoshop to temper the saturation and contrast. Oversampling is great, a little trick, never oversample at even multiples (like powers of two), since when you drop the resolution, even multiples will evenly stack pixels, often negating any averaging reduction you are shooting for. Use an oversample slightly more or less, or odd multiples of your target resolution (like for 1024px wide image, oversample at 2500px or so...) When you do that, reducing to the target resolution forces overlapping of same-region pixels, which is what nullifies the fireflies.

Also, never never *never* be tempted to turn on the post filters in render settings. You are destroying what little efficiency Iray has on its journey to convergence; you are adding a lot of overhead to the raycasting calculation and dragging out the render time, all while introducing yet another kind of noise to the system. Use the bloom filter only if you're feeling bohemian and artistic (also easily done in postwork), otherwise scrap anything that isn't the firefly filter, and handle it in post.

[Frank21]

Thank you Amber @Amberkat. There must be some technical reason why the DS denoiser doesn't have any way to graduate or moderate its effect. A slider would be nice. I suppose it could be a Nvidia or Iray thing rather than DS.

[John Lund]

@Reinecarola

some of my renders still have a lot of noise, whereas others render perfectly fine

I have the exact problem on a regular basis and I am 99.99% sure this is the reason:

Those that fails happens to be just about small enough to fit into the VRAM, BUT they are slightly to big for the GPU to be able to use the denoiser.

Use Scene Optimizer (https://zonegfx.com/scene-optimizer/) to make the footprint of the scene lighter, I can almost assure you that the denoiser will start working. It always does that for me anyway.

Note that the scene just has to be slightly smaller, changing the subd of the character from 2 to 1 and other items from 1 to 0 is usually enough (for me). You need eyes (and screen) better than an eagle to spot the difference. But test what works for you.

Another thing that works sometimes is to just restart DAZ.

[Niala]

Thank you Amber @Amberkat. There must be some technical reason why the DS denoiser doesn’t have any way to graduate or moderate its effect. A slider would be nice. I suppose it could be a Nvidia or Iray thing rather than DS.

Actually no denoiser have a slider. I use the intel standalone denoiser and it just decides for every pixel if it belongs to the actual texture or not. In the later case, it is replaced by a guess of what it should be with respect to its surrounding pixels and some AI magic. The result are generally good but may be slightly too crisp.
Actually, what I do is to render a larger image, to denoise it, to create a final image by mixing the original and denoised one and to rescale it. A mix of 80% denoised/20% original generally gives good results but it can be adjusted to give natural looking images.
All is done with a script that uses the intel denoiser and imagemagick to do all the other processing. The main interest of a script is to rapidly batch denoise all a render directory, for instance for an animation sequence.

[Abad]

Or, simply, use canvases and mix...
In this video, around 10 minutes, Versilius explain it...

Using Iray Canvases in DAZ Studio – 3D Shenanigans #13

[Frank21]

Hmmm... very interesting video @Abad. Thanks for the info.

[Author]

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