Copyright Goodheart-Willcox Co., Inc. Chapter 9 Mesh Modeling 227 Applying a Crease to a Mesh Model A crease is a sharpening of a mesh subobject, much like a crease in folded paper. A crease sharpens or squares off an edge or fl attens a face. This prevents the subobject from being smoothed. Creases can be applied to faces, edges, and vertices. A smooth- ness level of 1 or higher must be assigned to the mesh object for the creases to have an effect, but they can be applied at any smoothness level. Once a crease is applied, any existing smoothing is removed from the subobject. If the mesh smoothness is increased, any creased subobjects are not smoothed. Also, creasing an edge before an object is smoothed will limit the mesh editing capabilities. An example of where a crease might be applied is the bottom of a computer mouse. As the design of the computer mouse begins, the base of the mesh model is rounded when the model is smoothed. See Figure 9-17A. By creasing all bottom edges of the mouse, the bottom is squared off. See Figure 9-17B. A fl at bottom is a requirement of the design intent because the mouse must sit fl at on a desk. In another example, the trigger pads on the game controller shown in Figure 9-18 have been creased to create a fl at surface. When the conceptual design is fi nished, it can be converted to a solid. This will give the designer a unique shape to which buttons and joysticks can be added. This unique shape would be diffi cult, if not impos- sible, to create from scratch as a solid model. Once the command is entered, select the subobjects to crease. You do not need to press the [Ctrl] key to select subobjects, but fi lters should be used to make selection easier. Once the subobjects are selected, press [Enter]. This prompt appears: Specify crease value [Always] Always: If you enter a crease value, this is the highest smoothing level for which the crease is retained. If the smoothness level is set higher than the crease value, the creased subobject is smoothed. The Always option forces the crease to be retained for all smoothness levels. In most cases, this is the recommended option. MESHCREASE Ribbon Mesh Mesh Add Crease Type MESHCREASE CREASE Bottom Bottom Bottom is rounded Bottom is not smoothed A B Figure 9-17. Adding creases to a mesh. A—Before the creases are applied, the bottom of the mouse is rounded. This is obvious if the object is rotated (right). B—After the creases are added, the bottom is flat.