As a result, you will get the faces pointing to the outside of the model

and a clean, smooth surface (Figure 4.13).

Figure 4.13 - Clean smooth surface

Whenever you see dark spots at an object surface after applying a

Subdivision Surface modifier and a Shade Smooth, you probably have

an issue with Face normals. Enable the display of Face normals in the

Overlays menu to investigate and apply a fix.

You have additional options to handle normals in the Mesh → Normals

menu.

Tip: If you want to invert the normals of a face you can use the Flip

option from the Mesh → Normals menu.

4.2.3 Controlling smoothing radius with loops

Once you apply a Subdivision Surface modifier to an object, you will

notice that it will round the edges and corners for those 3D models for