Nurbs, points, polymesh, 3DS, WTH?

[InspirationTool]

Okay, so I've been playing with Rhino, and imported some 3DS files from 3d-cafe. They come in fine, but I find out they are "3d meshes", so I converted it to a nurbs with "meshtonurbs". I then created a rectangular solid and tried to subtract the model from the solid. I keep getting "boolean subtract failed".

This tells me that the nature of the information for the 3D object is critical to what I can do with it, how I can edit it, and how files are saved and opened in other programs.

I plan to do the Rhino tutorials, but they cover solids and surfaces (if the surfaces are nurbs, and the solid isn't a 3d mesh, what are the solids?) without going into much detail on the root representation of the objects.

Sooooo.... is there a good primer out there on this kind of thing?

(I did to a cnczone search first, BTW)

Thanks!

-Jeff

[ger21]

Think of a solid as a completely solid object. Cut it in half, and its solid all the way through. Think of a nurbs surface as an infinately thin sheet, whose surfaces are defined by mathematical formulas. And think of a 3D mesh as another infinately thin sheet, but composed of many small polygons (triangles only in the case of .s3d models).

Because nurbs surfaces and meshes have no thickness, booleans don't usually work with them. Most programs won't let you mix the two for boolean use.

Booleans are typically only used with solids, but sometimes even solids can cause problems with complex shapes.

Some programs only use meshes, some just nurbs, and some just solids. Because Rhino can do any of them, it can be a bit more complicated to learn. A good place to start might be to work through the tutorials on the Rhino site. Look under support > tutorials. The free user tutorials are at the bottom.