Understanding the denoising problem
Denoising is a relatively complex problem. And rarely does one solution fit all cases. In an earlier blog post, we explained the pros and cons of the new NVIDIA AI Denoiser that’s in V-Ray Next. Because it gives users a near real-time denoised solution, it’s a great option for lighting and scene composition. But it does have some limitations that keep it from being the best solution for final renderings.
Denoising and compositing
In the visual effects world, artists will output a large number of render elements to allow for adjustments in compositing. It’s common to split out many aspects of the render into different parts like specular, reflection, reflection filter, diffuse filter, lighting, and global illumination. The challenge then becomes to recomposite the beauty image using the individual elements. One issue that can come up is that each render element has to represent an exact contribution of the original beauty image or artifacts can appear, especially near edges.
Now imagine that you want to use the denoised image as the beauty. That would mean that all the render elements would also need to be denoised. If each render element is denoised on its own, then your recomposite back to a beauty image could have a lot of artifacts.
Let me explain how the new render element denoiser in V-Ray Next eliminates this problem by maintaining the correct contribution of the complete denoised image for each render element.
Temporal denoising
When you denoise an image, the algorithm tries to detect noise and smooth out part of that image through filtering and blurring, while still preserving edge integrity. If you are rendering an animation, this means that every image will be denoised separately. As each image is different, the denoising of each image will also be different. Those differences can result in swimming patterns as you go from frame to frame.
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