Warpy scanlines in sand

[WAS]

Trying to figure this out since yesterday morning. First I had to defeat the weird super dark shadow artifacts with smooth terrains which actually seems to come from non-clamped displacements (huh). Soft minimum and maximums to the scalar feeding sandwaves disp cured it more than subdivision.

Now, though I'm having strange effects along the horizon of a dune. The dunes terminator, and sand wave peaks have weird warped scanlines. I can't get rid of them. What are they? Absolutely nothing in the scalar info that should be creating these. Is this just lighting and angle creating artifacts? If you look in the foreground, it's not present, but middleground, there starts to be weird dark shadow lines on the peaks, and than they get closer together into the background.

This like my 20th attempt at trying to avoid this, and still can't get rid of them. I don't notice them as much in PT, but it's also slow as molasses with sand highlight and speckles (though looks 10x better).

Preview is zoomed in with TGs render view to see the issue better.

[Tangled-Universe]

Moire effect if you'd ask me?
What happens if you render it twice the resolution?
Increasing AA can also reduce moire, but it seems that the effect is mostly about feature size vs screenspace.

[WAS]

Moire effect if you'd ask me?
What happens if you render it twice the resolution?
Increasing AA can also reduce moire, but it seems that the effect is mostly about feature size vs screenspace.

You know, I think you're right. I'm rendering at 2200px buuut, even though Render View says it's at "100%" it's still down-sized to fit screen space, and I'm fairly positive that downsizing isn't using any robust algorithm for quality. It's just a preview of the render going.

Thanks Martin.

[WAS]

Yeah it looks like it's MPD/AA in Standard Render in the background. Things get rougher than they should, which when downsized in render view, looks like scanlines.

Edit: Shapes like these need high quality AA and MPD it looks like, even compression with JPEG severely distorts background stuff in shadow. MPD 0.7 AA7 here.