SolidWorks 2011 Parts Bible - Matt Lombard [175]
FIGURE 12.8
The Check Entity dialog box
Evaluating geometry with reflective techniques
Evaluating complex shapes can be difficult. A subjective evaluation requires an eye for the type of work you are doing. An objective evaluation requires some sort of measurable criteria for determining a pass or fail, or a way for you to assign a score somewhere in the middle.
One way to subjectively evaluate complex surfaces, and in particular the transitions between surfaces around common edges, is to use reflective techniques. If you look at an automobile's fender, you can tell whether it has been dented or if a dent has been badly repaired by seeing how the light reflects off of the surface. The same principle applies when evaluating solid or surface models. Bad transitions appear as a crease or an unwanted bulge or indentation. The goal is to turn off the edge display and not be able to identify where the edge is between surfaces for the transition to be as smooth as if the whole area were made from a single surface.
With all of the RealView functionality in SolidWorks that emphasizes reflective finishes and backgrounds that emphasize the reflections, sometimes the RealView Appearance and Scenes are all you need to employ reflective evaluation techniques. Chapter 5 covers all of the display information you need to make the most of RealView, Appearances, and Scenes.
Using Zebra Stripes
Zebra Stripes can be activated one of two ways, by choosing View⇒Display⇒Zebra Stripes from the menus or by clicking a toolbar button on the View toolbar. Zebra Stripes place the part in a room that is either spherical or cubic, where the walls are painted with alternating black-and-white stripes (although you can change the colors and the spacing of the stripes). The part is made to be perfectly reflective, and the way that the stripes transition over edges tells you something about the qualities of the faces on either side of the edge. Four conditions are of particular interest:
• c0 = faces contact at edge
• c1 = faces are tangent at edge
• c2 = curvature of each face is equal at the edge and the transition is smooth
• c3 = rate of change of curvature of each face is equal at the edge
The Zebra Stripes tool can only help you identify c0, c1, and c2, and only subjectively. This feature is of most value between complex faces. Figure 12.9 illustrates how the Zebra Stripes tool shows the differences between these three conditions.
FIGURE 12.9
Contact, tangency, and curvature continuity
Notice how on the Contact-only model, the Zebra Stripe lines do not line up across the edge. On the Tangent example, the stripes line up across the edges, but the stripes themselves are not smooth. On the Curvature Continuous example, the stripes are smooth across the edges. The part shown in Figure 12.9 is a surface model and can be found on the DVD with the filename Chapter 12 Zebra Stripes.sldprt.
Tip
You should rotate the model a lot when you are using the Zebra Stripes tool. Changing the density of the lines can also help, as can increasing the image quality (Tools⇒Options⇒Document Properties⇒Image Quality). Turning off the edge display may also help.
Using RealView
RealView Graphics display is only available to users with certain types of video cards. To see whether your card supports RealView, consult the system requirements on the SolidWorks Web site.
RealView causes reflections that can be used in a way similar to the reflections in Zebra Stripes. Rotate the part slowly and watch how the reflections flow across edges. Instead of black and white stripes, it uses the reflective background that is applied as part of the RealView Scene.
Cross-Reference
RealView techniques and usage are covered in more depth in Chapter 5.
Using Curvature