Understanding Edges and Surfaces
Another crucial SketchUp concept is about edges and surfaces. All models are constructed using edges and surfaces in SketchUp. Edges and surfaces are just what you think they are, as shown in Figure 2.16.Surfaces are always bounded by edges, and you need a closed figure created out of edges to create a surface. For example, you might use the Line tool to draw two lines, as shown in Figure 2.17.
When you connect the two lines with a third line to create a closed figure, SketchUp automatically recognizes that you’ve created a surface and colors it in, as shown in Figure 2.18.
TIP: Erase an Edge and Your Surface Is Gone If you erase one of the bounding edges of a surface, that surface disappears—it’s no longer a surface. You can, however, re-create the surface by redrawing the last edge—a process known as healing a surface.
FIGURE 2.16 Edges and surfaces.
FIGURE 2.17 Two lines.
FIGURE 2.18 SketchUp colors in closed figures.
You create surfaces from figures with closed edges, and SketchUp colors the surface in when it’s done. But what happens if you draw a surface and SketchUp doesn’t treat it as a surface and doesn’t color it in as a surface? Often the problem is that the edges you drew turn out not to be in the same plane. Because SketchUp snaps the lines you draw to the various axes or other already-drawn edges, and you’re drawing in 3D, it’s easy to create figures that are all in one plane by mistake. However, it’s hard to see that they’re not in the same plane. To check whether a surface is all in the same plane, use the Orbit tool to orbit around it in 3D.
Thanks :
Steven Holzner,
SamsTeachYourself Google SketchUp 8 in 10 Minutes
