xNormal normal map artifacts

feracon

Hi,

I'm at a loss for why I'm getting two artifacts in my normal map. The model is a simple chair, low poly, high poly and cage made by transforming vertex components of low poly in Maya.

-Problem-
Subtle splotches are appearing on seat of the chair over the slight incline of the groove, and more apparent splotches are appearing under the seat edges.

-Setup-
The low poly high poly model's surfaces are as co-planar as possible and the cage envelopes both. In the pictures below: Grey - Low Poly, Yellow - High Poly, Red - Cage.

-xNormal-
Search depth - .5 (tried .1 and 1, same results)
Use cage - Checked
Mikk - TSpace Compute binormal in pixel shader - Checked (tried unchecked)

-Low Poly UVs-
Yellow dots mark the shells with artifacts. I've split off hard edges of the chair and padded their shells for bleeding.

I'm out of options to try, if anyone has any ideas please please chime in!

PS- not 100% sure if this is the right place to post this, apologies if it's not.

EDIT: Forgot to mention my renderer for the screens below is Marmoset Toolbag, I know nothing about it, I've just dragged in the low poly and attached the normal map to the default shader.

feracon

Attached normal map with artifacts. Anyone have an idea what could be causing the three bright colors in the upper left shells? Those seem to be the issue.

Bek

http://www.polycount.com/forum/showthread.php?t=148303

Bartalon

In addition to Bek's post, you should also check out this thread:

http://www.polycount.com/forum/showthread.php?t=107196

TL;DR:

Strange banding in the seat area of your chair is due to a near-perfect match between your high and low poly, and your output file format doesn't have enough bit depth to compensate.

The splotches are caused by ray cast errors, check your cage setup. This is also possibly due to intersecting geometry depending on how you made your model.

The dark lines along some of your edges are due to edge smoothing mismatches compared to your UVs when baking a normal map (if you have a UV split, you should usually have a hard edge there, and vice versa)

An airtight mesh will always produce a better bake than one with intersecting geometry, and will make better use of your UV space.

feracon

Thanks for taking the time to help me out guys. I'd looked through a few articles before posting but they all had dead image links.

I'll return if these dont fix my issues but it sounds like you guys nailed it.

Thanks again!

EDIT: After reading and watching everything in those two articles...mind blown. Can't believe how reliant on luck some of my good results have been. Thanks again for sharing.

WarrenM

(if you have a UV split, you should usually have a hard edge there, and vice versa)

Not quite. If you have a smoothing split, you have to have a UV split. But the reverse isn't true.

Bartalon

Indeed. That's why I said usually

Eric Chadwick

Well to be clear, "usually" is ok for making hard edges... that's optional.

But you should always split UVs where you have hard edges.

This is necessary to avoid shading errors, because a contiguous uv can't represent the sudden shading change from a hard edge.