Copyright Goodheart-Willcox Co., Inc. 164 AutoCAD and Its Applications—Advanced Lofting is used to create open-contour shapes such as fenders, automobile interior parts, fabrics, and other ergonomic consumer products. Figure 7-18 shows the use of open 2D splines in the construction of a fabric covering. Notice how each cross section is intersected by the guide curve. There is a cross section at the beginning of the guide curve and one at the end. These conditions fulfi ll the rules outlined earlier. CAUTION CAUTION Guide curves only work well when the surface control is set to Smooth Fit (LOFTNORMALS = 1). If you get an error message when using guide curves or the curves are not refl ected in the end result, make sure LOFTNORMALS is set to 1 and try it again. Controlling the Loft with a Path The Path option of the LOFT command places the cross sections along a single path. The path must intersect the planes on which each of the cross sections lie. However, the path does not have to physically touch the edge of each cross section, as is required of guide curves. When the Path option is entered, you are prompted to select the path. Once the path is picked, the loft is created. The cross sections remain in their original positions. Figure 7-19 shows how 2D shapes can be positioned at various points on a path to create a loft. The rectangular shape does not cross the path. However, as long as the path intersects the plane of the rectangle, which it does, the shape will be included in the loft defi nition. The last shape at the top of the helix is a point object, causing the loft to taper. A B Figure 7-18. A—The open profiles shown in black and the guide curve shown in color will be used to create a fabric covering for the three solid objects. B—The resulting fabric covering. This is a surface because the profiles were open.