From: Terry T. Wohlers (
Date: Thu May 02 1996 - 19:02:14 EEST

Marshall Burns wrote:

> I thought GIF and JPEG were 2-D formats, while a wireframe is necessarily
3-D, so that a conversion would not make much sense. Can somebody please
straighten me out on this?

The goal here, as I understand it, is to create a file of vector data from
raster data. The vector file would become a wireframe that's either 2D or 3D
(vector data that contains Z values). Converting an image in gif or similar
raster format to vector data can be achieved in a number of ways as described by
others here. Some involve manual tracing while others are semi-automatic using
special software. The technique used usually depends on what exactly you're
trying to accomplish and the resources you have available to you. You can store
the converted vector data in a number of formats including IGES, DXF, OBJ, and
STL. That's the easy part.

It's possible to assign a Z value (height) to each of the grayscale pixels in
the gif file. These pixels have preassigned values that can range from 0 to 255.
You could assign the darkest pixels -- those which approach 0 -- a Z value of 10
mm. Likewise, you could assign the lightest pixels -- those which approach 255
-- a value of 0 mm. So everything in the middle gets assigned a height between
0 and 100 mm. Are you beginning to see how a 2D picture could take on 3D shape?
I was given the opportunity to work on a project that uses this technique and it
works well. We even built SLA and FDM parts from the data and they turned out
very good.

I could go on and on but I won't. I will say this: High resolution data can
produce some awfully big files. We had to develop special decimation techniques
that reduced the polygon count. And before getting to polygons, we were careful
not to use any more point data than absolutely necessary.

Hope this provides some clarification.

Terry Wohlers
Wohlers Associates

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