The Concept of Normals

A normal in the 3D world refers to the vector that is perpendicular to a surface. A face or polygon contains only one normal direction. The normals indicate the front and back side of faces. The front faces (polygons with normals) will be rendered, and then appear in the 3D programs, while the back faces will not. Therefore, if you turn the camera towards the back faces then they may look transparent and you will see through them. You may use this feature to create any mesh inside-out such as turning a ball into a sky dome.

View from the front side of the mesh

View from the back side of the mesh (transparent)

Normal and Faces

  1. The directional line of the left face.

  2. The directional line of the right face.

  3. The angle formed by these two faces.

Show Normal Directions and Adjust Normal Display Length

  1. Pick one or more mesh nodes to show the normal line. Execute the Modify menu >> Edit Normal command.
  2. In the Edit Normals panel, enable the Show Normal Directions box.
  3. Drag the Normal Display Length slider to decide the length of the normal lines.