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Displacement moire issue?

Posted: Tue Nov 25, 2008 1:16 pm
by Mr Whippy
Hi all,

I have had this problem before, trying to simulate the same carpet.

The texutre is about 512x512 greyscale, you can see the dummy in the screenshot mesh for the UVW coords in 3DS Max.

I'm just wondering where the moire pattern is coming from, and why it seems to be following the form of the sub-d mesh.

Image


Does anyone have a solution to this, like a better way to mesh? Should it be made from squares of the same size as much as possible... but surely it will still pinch at the edges?


Thanks

Dave

Posted: Tue Nov 25, 2008 6:55 pm
by JesperW
No solution unfortunatly, all I can say is I had the same problem as well on my sea surfaces. It seems the displaced surface is oscillating for every other polygon of the underlying object.

In the end I gave up trying to solve it...

Posted: Tue Nov 25, 2008 7:03 pm
by Blitzor
It has to do with the resolution of the rendered image and the resolution of your bitmap image... Try changing the resolution of either and you will see it go away.

Posted: Tue Nov 25, 2008 7:31 pm
by Bubbaloo
No, it is a problem of non-uniformly sized polygons ranging from very small to large. Try a higher resolution 16 bit displacement map and high precision if you can't get the mesh divided up properly. Try starting with a cube and subdivide it instead of starting with a cylinder.

Posted: Tue Nov 25, 2008 9:27 pm
by polynurb
maybe reading to the end of this page helps you :

http://www.maxwellrender.com/forum/view ... c&start=30

it is certainly the best to keep the subdivisions as equal as possible..

Posted: Tue Nov 25, 2008 10:20 pm
by Blitzor
Ah this is displacement which is geometry dependent... Then yes you need listen to the guys that posted above. :P

Posted: Wed Nov 26, 2008 12:37 pm
by Mr Whippy
Ah, yep, I dropped over an even quad plane about 15cm grid, trimmed the edges and tidied it up, then made the disp map 16bit and it seems much nicer now.

I did notice though that after my sub-div from a 30cm grid to 15cm grid it got a bit of pattern back again, before I used the higher bit disp.map...

Seems to be a combo of relative map/tri sizes and the bit-depth as said. Here is hoping this is made a bit more user friendly in future :)

Dave