I think I’ve found the problems with my C# drop-cutter algorithm. The first bug was a trivial one where in the edge-test the rotation of the segment-under-test was messed up. The second one was not the facet-test itself but incorrect surface normal data. There’s something going on that makes pre-calculated surface normal data not ‘stick’ [...]

I’ve now ported my Matlab work on Drop-Cutter to C#. It can load an ASCII STL file and then run the drop cutter algorithm. Not trying to take too much on in the beginning, here’s an example of the output with only two triangles as input not quite there yet! (who can spot what’s wrong?) [...]

Together with another Anders (from Sweden) I’ve worked a little bit on some C# code for rendering stuff in OpenGL. The idea is to put together a basic framework where CAD/CAM ideas and algorithms can be tested. Above one of the first useful screenshots where I’ve rendered an STL file with about 22k triangles. The [...]

The third and final test in the drop cutter algorithm is to drop the cutter down so it touches an edge. The vertex and facet tests were quite easy, but this one requires a bit of calculations. I’m following Chuang2002. To simplify things we first translate the tool in the (x, y) plane to (0, [...]

Continuing with some random thoughts on CAM algorithms, here’s a diagram I drew in response to a question on offset ellipses posed by Julian Todd. (click image for high-resolution version) The task is to find an offset ellipse to a given ellipse (magenta). The offset ellipse (blue) should lie a distance T, measured along the [...]