Object turning black when applying material

[Sirvilmos]

Hello,

I created an object in Blender and exported as an obj file. After importing into zmod, I apply a mesh material to the object and it turns black in certain spots like there's a shadow. I can't seem to figure out the issue as it doesn't happen every time with every object. I've tried normals, flipping, and applying different materials with different adaptations. When using default material without shaders, it looks normal with the usual gray texture. See attachments for example.

Thank you,

[Oleg]

mesh shader uses bump-mapping texture to adjust surface shading. Bump-mapping requires surface tangents to be computed (evaluated on uv-mapping of triangles). An object coming from .obj file is never equipped with tangents, so either refuse from using mesh shader, or assign proper bump texture and calculate tangents. Surface\Normals\Calculate tool can do this (given that polygons are properly uv-mapped onto texture).