Copyright Goodheart-Willcox Co., Inc. Chapter 10 Advanced Surface Modeling 245 Creating Surfaces from Existing Creating Surfaces from Existing Surfaces Surfaces In addition to creating surfaces from profi le curves, you can create surfaces from existing surfaces using the SURFBLEND, SURFPATCH, SURFOFFSET, SURFFILLET, and SURFEXTEND commands. These commands are discussed in the following sections. Surface models created with these commands are created as associative surfaces by default. This maintains associativity between the surfaces used to create the surface and the resulting surface. Blend Surfaces When working with surface models, there are situations when you need to “blend” together surfaces that do not meet or touch. The SURFBLEND command is used to create a blend surface between two surface edges or two solid edges. When blending surfaces, you select the surface edges to blend, not the surfaces. Select the SURFBLEND command and then select the fi rst edge to blend. Press and hold the [Ctrl] key to select the fi rst edge or use the edge subobject fi lter. You can select multiple edges or use the Chain option to select a chain of continuous edges. Press [Enter] after defi ning the fi rst edge. Next, select the second edge. Select a single edge or multiple edges, or use the Chain option to select a chain of continuous edges. When you press [Enter], a preview of the surface appears. You can press [Enter] to accept the default settings, as shown in Figure 10-9, or you can use the Continuity and Bulge magnitude options to specify the continuity and bulge magnitude settings at the edges. Different settings can be applied at each edge. The settings are similar to those when creating a loft, as discussed in Chapter 7. Continuity defi nes how the surfaces blend together at the starting and ending edges. The following options are available: • G0 (positional continuity). This option creates a sharp transition between surfaces. The position of the surfaces is maintained continuously at the surface edges. This option is used for creating fl at surfaces. • G1 (tangential continuity). This option forms surfaces so that the end tangents match at the edges. The two surfaces blend together tangentially. This is the default option, as shown in Figure 10-9B. • G2 (curvature). This option creates a curvature blend between the surfaces. The surfaces share the same curvature. Examples of blend surfaces with different continuity settings are shown in Figure 10-10. SURFBLEND Ribbon Surface Create Surface Blend Type SURFBLEND Select the first edge A B Select the second edge Figure 10-9. A blend surface is created between two existing surfaces by selecting a starting and ending edge. A—Two existing loft surfaces. B—The model after creating a blend surface with the default settings of the SURFBLEND command.