Hair cap issues when rendering in Blender

jwcjaygaines

This problem occurs in the Cycles render engine - in Eevee it doesn't exist. There's a couple of hair caps/scalps that I have purchased that are "poking through" and creating dark artifacts in areas where they're supposed to be transparent. This is my current workflow:
- Import the hair cap via Diffeomorphic on its own rig.
- Convert to MHX under Rigging
- Combine the hair cap rig with the base model rig using Merge Rigs under Corrections (uncheck all options).
- Transfer Shapekeys from base model to hair cap under Morphs (PJCMs, Expressions, etc.)
- In Modifiers, add Smooth Corrective and Subdivision Surface under the Armature.
- Leave Materials as-is (Alpha Hashed on both options)
When the model is static, all looks well. But if I import an Expression, random parts of the hair cap will show up in the render as dark splotches in areas where it's supposed to be transparent. So far I've noticed it on the Faux Hawk Hair cap and the Chuck Hair - Short Hair caps. Is this a Cycles setting issue, a material issue, or something else like unnecessary/duplicate shapekeys? 

TheMysteryIsThePoint

Bump up the Transparency Light Rays?

Krys Kryngle

Usually this is caused by the scalp intersecting with the character mesh.  You can try adding a shrinkwrap modifier after the subdivision modifier.  I've had issues also.  It's a pain sometimes, depending on the character, hair, and all the other variables.  

One surefire way to eliminate the issue forever is to bake the scalp texture into the character texture.  This can be done using the 'Bake to Target' feature in Simplebake.  I know it's a paid addon but it works really well.

 

 

Padone

- In Modifiers, add Smooth Corrective and Subdivision Surface under the Armature.

Smooth corrective of course affects the mesh, that's probably the cause of your issue. If you already transfer the morphs you don't need it. Also note that smooth corrective depends on the mesh, so different topologies will generate different deformations. For this reason usually you use smooth corrective on the base mesh, then a surface deform for the other meshes to follow, again not necessary if you transfer morphs.

 

jwcjaygaines

Thanks for all the suggestions! Padone, I think it was the Smooth Corrective like you said. I'll keep experimenting. :)