Shade Smooth Artifacts in Blender
Dark patches after Shade Smooth and missing Auto Smooth
Also known as: Blender Auto Smooth missing · Blender shade smooth dark · Blender smooth by angle · Blender shade auto smooth · Blender shading artifacts
Quick answer
Dark patches or odd gradients after Shade Smooth appear because smooth shading averages normals across edges that should stay sharp. In Blender 4.1 and later, Auto Smooth was replaced by the Smooth by Angle modifier: choose Object > Shade Auto Smooth, set an angle such as 30 to 60 degrees, and sharp edges stay crisp. Older versions have an Auto Smooth checkbox in Object Data properties.
How to fix it
For hard-surface models, add bevels or use weighted normals so large flat faces shade cleanly, and mark sharp edges where you need them. If shading still looks wrong, check for flipped normals and non-uniform scale. When exporting to a game engine, export normals so the engine keeps the shading, and bake normal maps with the same smoothing setup.