Strange artifact on normal map always appear in meshes with this shape.

G0056

Hi, while modeling some props for games I've encountered the same error 2 or 3 times, and I wanted to know how to solve it becouse it's very annoying and I don't understand why it happen.



How should I model this kind of shape? I had to do it in 2 different models, and always gives me problems. While modeling all looks normal, it doesn't give me troubles. The troubles comes when I start baking my normal map from the highpoly model to my lowpoly model:



I always end having that strange artifact baked on the normal map in the same spot.


I don't understand why this keeps happening, so I wanted to know if someone could tell me how to solve this kind of problems, becouse I didn't find anything similar to this on internet. I'm using blender to model, and substance painter to bake highpoly to lowpoly(baking by mesh name).

FrankPolygon

This looks like a normal map gradation issue. There's a few things that can cause this but some likely factors are: a lack of hard edges, mismatched triangulation and mismatched tangent space.

Uncontrolled smoothing on flat (planar) surfaces can result in extreme gradients in baked normals. Long thin geometry will produce long thin triangles that contribute to baked normal gradation. Using hard edges to control smoothing can help reduce normal gradation.

Mismatched triangulation can occur when the mesh triangulation isn't consistent across baking, exporting and rendering. Changing the geometry (specifically the triangulation order) after baking means the normal map data won't match the geometry and this can cause shading errors. Relying on auto triangulation can cause variation because different applications may use different methods for calculating triangulation. Triangulating the finished mesh before moving on to baking, exporting and rendering will eliminate this error.

Mismatched tangent space can occur when the baking and rendering applications use a different method to calculate the normals. Ensuring that all applications in the workflow are using the same tangent space will help ensure that the normal maps behave consistently across all applications.

This thread explains most of these issues and provides some solutions: https://polycount.com/discussion/107196/youre-making-me-hard-making-sense-of-hard-edges-uvs-normal-maps-and-vertex-counts/p1

This video by Alec Moody is an excellent resource for this topic: https://youtu.be/ciXTyOOnBZQ

Also check out the Toolbag baking tutorial (Click on "Best Results"): https://marmoset.co/posts/toolbag-baking-tutorial/

Kanni3d

Make that problematic face planar, and rebake. Problem solved if that bulge in your low-res mesh isn't intentional.