As @ said it can be about smoothing group but for my opinion it seems to be caused by triangle on triangle. In 3DS Max you have a function in the polygon editor to clean the mesh from every unclosed triangles. As @trolltime809 said
As @ said it can be about smoothing group but for my opinion it seems to be caused by triangle on triangle. In 3DS Max you have a function in the polygon editor to clean the mesh from every unclosed triangles. As @trolltime809 said