Arnold displacement small problem

obloquy

Hey, so I'm just doing my first test with displacements extracted from zbrush using the Flippednormals quick tutorial (https://www.youtube.com/watch?v=-ThBTEc8L_M), everything seems to have worked sort of, however I'm getting some weird artifacts as shown in the pic and it looks as if the lowest sub division extracted from is showing though in places so you can see visible polygon faces (see pic).  Also looking at the side by side the arnold render looks a bit soft and 'bloated'...

Can anyone point me in the direction if this has happened before?  

 

oglu

Could you show your subD settings for the arnold render. And the color settings in the texture node. 

musashidan

Arnold is expecting a mid of 0. Yours is exported at 0.5

Not saying this is your issue, but it's something to know.

obloquy

Oglu - I set the subdivision iterations to 3 in arnold and checked auto bump like the tutorial suggested



Musahidan - The tutorial suggested a mid value of .5 from zbrush balanced with a -.5 in the scalar zero value.  Not sure if thats the issue and I should be just extracting it at 0 mid value and then leaving the scalar zero at 0 too...

musashidan

The scale is very important because it's sort of 'baked' and there is a direct correlation between the ZB map the the model scale. What scale? It does look to be bloated. 

Yes, you can do it in the shader but why would you when you can bake the map at mid 0? Mid 0 is expected for a 32bit exr.

The problem could also be the low res of the map as you are only using a single tile. Try baking at 4k instead.

oglu

For the subd you have to use the same level as in zbrush. If your highres in z does have level 3 its ok. 

obloquy

Thanks musahidan, I managed to solve the faces showing through the mesh by setting the "UV smoothing" in Maya to linear rather than pin corners as I didn't check uv smoothing in Zbrush when I exported the disp.

I set the scale to 1 in the map, and the model scale is human size (if thats what you meant?)  Will try extracting at 4k and post results

Did a comparison of 0 midvalue to 0.5 and there was defiantly inflation...

obloquy

oglu said:

For the subd you have to use the same level as in zbrush. If your highres in z does have level 3 its ok. 

Ahh - my high res mesh in zbrush has 5 sub divs.  I set the iteration in arnold to 3 and ticked Auto Bump as the guys from the flipped normals tutorial said that you should set it to however many sub divs you have in zbrush but by ticking Auto Bump it isn't required as  apparently the details that can't be displaced will be put into the bump map for a crisper result.  Its at 19:47 https://youtu.be/-ThBTEc8L_M?t=1187.  But not sure now as you suggest putting it at the zbrush highest sub div level

oglu

there are three things to get better displacement.
1. a lot of geo int he base model, the topo should follow the shape
2. highres textures, if one 4k isnt enough go with UDIMs
3. never cut your UVS to pole verticies, never cut the uvs to V shaped islands

obloquy

Ahh right thanks very much Oglu for the info.  I did a 4k map and render set to the number of sub iterations i had in zbrush and it defiantly looked crisper... still not sure if it looks inflated but when I do a comparison with zbrush and adjust the light source in zbrush to match arnold it looks the same pretty much