Copyright Goodheart-Willcox Co., Inc. Chapter 10 Advanced Surface Modeling 253 Extending Surfaces You can add length to an existing surface using the SURFEXTEND command. When extending a surface, you can specify whether the new surface is created as a continuation of the existing surface or as a new surface. The surface extends to a new length using the specifi ed distance. Select the SURFEXTEND command and select one or more surface edges to extend. After selecting an edge, press [Enter]. A preview of the extended surface appears and you can drag the cursor dynamically to set the distance. You can also enter a distance by typing a value. The Expression option allows you to enter a mathematical expres- sion for the extension distance. If you specify a distance and press [Enter], the surface is extended using the default settings. See Figure 10-20. Before specifying the extension distance, you can use the Modes option to specify the extension mode. The two options are Extend and Stretch. The default Extend option is used to extend the surface in the same direction as the existing surface and attempt to maintain the surface shape based on the surface contour. The Stretch option is also used to extend the surface in the same direction as the existing surface. However, the resulting extension may not have the same surface contour. After specifying the extension mode, you can use the Creation type option to set the type of surface created. The two options are Append and Merge. The default Append option is used to create a new surface extending from the original surface. This option results in two surfaces instead of one surface. The Merge option is used to extend the surface as one surface. After extending a surface, you can use the Properties palette to edit the extension distance. Exercise 10-7 www.g-wlearning.com/CAD/ Complete the exercise on the companion website. Trimming Surfaces Trimming Surfaces The SURFTRIM command can be used to trim surfaces or regions using other existing surfaces. You can trim any part of a surface where the surface intersects with another surface, region, or curve. In addition, you can project an existing object onto a surface to serve as a trimming boundary. The object to be trimmed and the cutting object do not have to intersect. When an associative surface is trimmed, it remains associative and retains the ability to be modifi ed by editing the cutting object. SURFEXTEND Ribbon Surface Edit Surface Extend Type SURFEXTEND A B Selected edge to extend Figure 10-20. Extending an existing surface using the SURFEXTEND command. A—The original model. B—The extended surface.