I've created a simple procedural wood texture for a ceiling fan I'm modeling. Unfortunately the usually excellent AI denoiser from 2.81 is smoothing out most of the texture details. Any suggestions for how to preserve the details better besides cranking up my samples a ton? Even at 1000 samples it washed out a lot of the details, though it was better.
AI Denoisers use algorithms to guess which pixels are fireflies, and what colour that pixel was supposed to be. The algorithms are limited to the data that it can collect from the Denoising Data and the surrounding pixels. Thus, if insufficient data has been passed to it (not enough samples), the denoiser will create a "washed out" effect where you're losing detail. In truth, the denoiser will almost always cause loss of detail, it's just that when the sampling is high enough, the loss of detail is negligible.
You haven't done anything wrong with the compositor nodes, you're going to have to increase the samples in this case.
If you're worried about render times, check out this video by BlenderGuru. It was created pre-2.80, but much of the content is still relevant.
Do you have the Progressive Refine option enabled by any chance? The Intel AI denoiser doesn't work with it, resulting in blank image data for the Noisy Image (which you should switch to because there is a difference), Denoising Normal and Denoising Albedo sockets. I was having trouble with it myself and found this out today (see link below). I also found, through much testing, that you can get a fair bit of texture blurring with your particular node setup when Progressive Refine is enabled in the Render Properties, probably because the denoise node has almost nothing to work with.
EDIT: Just wanted to update my original post from February with some new info regarding Intel's denoiser. As of Blender 2.90, the Progressive Refine option now works with it properly. It now works with the 3D viewport as well (useful for previews) and when doing final renders too. This is great news IMHO, as it means one is no longer forced to buy an Nvidia graphics card just to have these options. I also feel that Intel's OpenImage denoiser works slightly better than Nvidia's OptiX option, plus there's the fact that it isn't limited to just Intel CPU's. I hope this info helps all those whom read this message! ;)