An easy way to see the difference is to 'extrude' a circle in FreeHand into a 'cylinder.' You'll find that initially that 'cylinder' still has a circular (not elliptical) end-something that would not result from any actual projection of a 3D cylindrical model in which you could see the side of the extrusion. An example of that would be FreeHand's rather cheezy 3D Extrude. Your comment above suggests that Illustrator's 3D Effect is merely a 2D construction that is not derived from a 3D model. The difference in AI's 3D Effect, Dimensions, Satellite 3D (predated Dimensions), etc., is that instead of resorting to rendering as 2D poligonal facets (which would be impractically tedious to manipulate thereafter), they try to render the artwork as if you had drawn it yourself in AI, using stacks of shapes similar to what you would get from expanded AI blends, etc.

(ex: RainStorm Swift3D is a vector 3D modeler/renderer similar in level of sophistication to the sadly defunct Adobe Dimensions, upon which Illustrator's 3D Effect is based.) But all of these create a 3D model and then renders it to 2D artwork (either vector or raster). Some render as vector artwork, but usually as polygonal facets. Zaxwerks 3D Invigorator is an example of an Illustrator plug-in that does that. Most conventional-wisdom dedicated 3D programs render a raster image.

(We don't have commonplace 3D holographic projectors yet-we're still limited to viewing on 2D screens.) The difference is in the nature of the resulting 2D rendering. All 3D programs render a 2D flat image (or projection) of the model.

Illustrator's 3D Effect does indeed create a 3D model, in the same sense that any conventional-wisdom 3D program creates a 3D model. Shaded and extruded or rotated to look 3D. THe results of the effect are a flat, 2-dimensional object that has been The thing to remember is Illustrator's 3D effects do not create 3D objects,

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