When a 3D model’s edges seem hard during rotation, it’s typically due to flat shading (per-face lighting) or incorrect normal/edge split settings that prevent smooth light blending.
Flat shading calculates light for each face individually, so edges stay sharp as you rotate—smooth shading blends light across vertices to soften edges. If normals (surface direction guides) aren’t averaged or edge splits are misapplied, the model won’t smooth edges during rotation.
To fix this, try switching to smooth shading in your 3D software (e.g., Blender’s “Smooth” tool) or removing unnecessary edge splits—this often makes edges look natural when you rotate the model.