Reversing surface normals

When you apply a fur description to a surface, each hair making up the fur description points in a direction normal (perpendicular) to the surface by default. This direction is called the surface normal. When the fur does not display consistently on a model it may indicate that the surface normals are oriented inconsistently.

1. Dolly the camera so you can view inside the arm.
   

   The fur feedback is pointing towards the inside of the arm.

   In this model, the fur was applied to the inside of the leg, arm, and head surfaces because the surface normals on these surfaces are pointing in the wrong direction. There are several reasons why this can occur, including when a surface is duplicated with a negative scale value.

   To correct this, you’ll need to reverse the surface normals on the legs, arms, and head surfaces of the model.

   NoteReversing the surface normals (Polygons menu set: Normals > Reverse) is useful when you want to change the surface direction (that is, whether the surface is oriented inwards or outwards in relation to the model). For example, duplicating a surface across its axis of symmetry can reverse the surface normals on the duplicated surface. Using the Reverse Normals feature corrects this.

   When a character has existing animation rigging or texturing and you need to assign fur, the desired technique for reversing the orientation of the fur feedback is by reversing the fur normals (Fur > Reverse Fur Normals). Reversing the fur normals leaves the surface direction unchanged.

To reverse the surface normals

1. With only the legs, arms, and top head surfaces selected, switch to the Polygons menu set and then select Normals > Reverse > .
2. Set the Reverse normals on setting to Selected faces and then click Reverse Normals.

   The normals of the selected polygon surfaces are reversed so that the fur description points in the correct direction.

   

Before proceeding to the next section, return to the Rendering menu set.