On 30/06/2020 03:41, Chris Albertson wrote:
Technical an STL is a list of triangles where each vertice is given a
location in 3D space.  Circles and curves are all replaced by polygons.

The triangles can be large if the model consists of large flat areas, but as you say, anywhere that is a circle or curve in the original 'model' is translated into a series of straight lines. Not unlike early 'simple' gcode which could not handle arc's and cut them as a aeries of straight line segments. The 'accuracy' depends on the number of segments, so while 'pixels' is not totally accurate, it is a reasonable analogy.

What you can do is slice an STL 'image' and then do the equivalent of a raster scan to convert lines below a certain resolution back to arcs or circles but I don't think anything has been written yet that would return the construction objects of the original model?

I remember being given a TurboCAD 3D model of a locomotive wheel to cut on the mill, but had to ask for 2D slices from which to produce usable gcode.

Lester Caine - G8HFL
Contact - https://lsces.uk/wiki/Contact
L.S.Caine Electronic Services - https://lsces.uk
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