|As I reviewed my last several
columns trying to come up with a clever idea for this one, I realized that it's
been quite a while since I wrote about Generic 3D (3DD). Actually, I found that
to be a little surprising, because I use it at least as much as CADD, and more
and more people are getting interested in 3D, especially because of the new
Autodesk 3D Concepts, which builds on the strengths of Generic 3D.
Why then, no tips? Is everything so self-evident in 3DD that no tips are required? It turns out that I don't really think of using 3DD as running a program. I treat it like building a model, and my thoughts and potential tips tend to get pretty application-specific - more about how to build something in particular rather than how to run the program. However, there are several techniques 3DD veterans use which might not be so obvious. Here are a few, in no particular order.
Angled Entities: Never, never, almost never, try to draw anything on an angle. Rotate the cursor into position and draw in the new position instead. Several commands are available for rotating the cursor, depending on the information that you have. Cursor Align (KA) aligns to an existing polygon, Cursor Rotate (KR) allow arbitrary rotations, and KS rotates the cursor into one of six standard positions.
Quick Hidden Line: For quick hidden-line checks on more complex drawings, rendering to the screen is quicker than vector hidden-line removal. Switch to 3D Dot-Plot (XD), then render (RN). To emulate a hidden-line view visually, change the Fill (F) option of Render Colors (RK) to Black and turn off the light source (LO) before rendering.
Extra 2D Lines: Before using saves 2D drawings in CADD (special versions of 3DD drawings saved in 2D format), strip them. In 3DD, several lines might be in the same place on the screen, which is OK, because when you move around or rotate things, you want them to appear. However, in CADD, these stacked-up lines have no use. Use the Strip program provided with 3DD to eliminate the extra lines.
Intersection Points: Probably the mot useful commands in all of Generic 3D for the advanced user are Intersection Point (IP), Move Point (MP), and Window Stretch (WS). To lop of the top of a cylinder at an angle, for instance, forst draw a polygon through the cylinder at the appropriate angle (rotate the cursor and use Ortho - see above). Next, use IP to find all of the intersections with the edge of lines of the cylinder and the plane. Finally, WS all of the points of the cylinder to the intersection points and erase the cutting plane.