I've been working on a model, and noticed a weird issue in Blender, when I used the Shade Smooth option, it makes black triangles in the model. Normals are calculated properly. I'm not really sure what cause this issue or how to fix it.
Sounds like the same question as this question on black triangles See the comments on that question - The problem appears when using smooth shading on a geometry containing a vertex that is connected to more than one n-gon. Turn those faces into quads and it disappears.