How to prevent or remove moiré patterns?

xlpasstest

In the rendered image yesterday, moiré patterns appeared, which left me at a loss.

Can someone tell me how to prevent this from happening in the future?

Or how to remove it when it occurs, such as using Photoshop (YouTube videos are not helpful for me).

crosswind

You can try: go to Render Settings pane, Filtering > Pixel Filter Radius, keep the value > 1.3 or more...

xlpasstest

crosswind said:

You can try: go to Render Settings pane, Filtering > Pixel Filter Radius, keep the value > 1.3 or more...

Thank you, this solved my problem. 

surv0101

crosswind said:

You can try: go to Render Settings pane, Filtering > Pixel Filter Radius, keep the value > 1.3 or more...

I have been dealing with this for over a year on and off.  I didn't know what it was. I certainly didn't know there was a name for it, lol. Well in my favorite render settings somewhere down the line I had changed the pixel filter radius to .80.  Why? I don't know, it was in a YouTube vid.  Well I took your advice and increased the value to 1.3, and everything is looking great and the swirly things in the cloth are gone. Thank you!!!! You saved the day!

Padone

As an explanation, moire patterns appear for high frequency textures, where there's lots of details which the render engine can't pick correctly for the rendered pixels. This typically happens with 4K 8K textures. One way is to resize to 2K which will also benefit the vram if you don't really need the closeup details as in the example image above. Or increase the pixel filter as suggested by Crosswind, which will smooth the details together with artifacts in general.