Cut a section thru a 3D wireframe in AutoCad2002

[gakare]

I'm new to autocad. I need to cut a section thru what appears to be a 3D wireframe ( The surface originated in Catia, but I recieve it in wire ). I can do it in Cadkey by drawing a line (not a plane) where I will cut and using the section command. Points are constructed where my section line intersects each wire. I then connect the points. How do I do it in AutoCad2002 ?

 

[starry]

You can do this by snapping to the apparent intersections of the cutting line and the wireframe lines.
Make a viewpoint above the wireframe object, so that you are looking down at where the cut will be. You will be viewing the cutting plane as an edge line, if it was there.
Set the elevation (Z height) with the ELEV command (or set properties of Z height) at some level above or below the 3D wireframe. Draw a line representing the cutting plane edge on another layer and in another color.
From your viewpoint (which you can save, by the way, in the VIEW command) you can draw a line or segments of lines, or a pline, or a 3D pline from one point to the next on the wireframe. Use the running Osnap function apparent intersection to make line endpoints where the cutting plane edge line seems to make intersections with the wireframe lines. This will give you straight sections of line between the apparent intersections. That will work if the wireframe surface you cut is flat.
If the surface of the 3D wireframe is curved concave or convex or some combo in the region of the cutting line, you will have to determine that curvature from adjacent wireframe lines. You can draw plines or arcs in the cutting plane that will be close to the true sectioning edge of a curved or complex surface.
It would be better to convert the wireframe to a solid, and use a sectioning tool in 3D solids to make this cut. But that may not be possible with your exported wireframe, or without other 3D software.