mesh sample.stl (167.9 KB)
In a mesh like this ^ we can see some parts being some generic triangulation, but some others being from obvious solid boolean operation from a revolved shape.
Edges there have a more coherent structure, if we “pair up” edges around every vector we might able to retrieve “U” and “V” isocurves/polylines of the original revolved shape.
Do you know any tool or logic to go in this direction?
(A first step would be to quadrangulate the mesh, probably… but maybe not, I might want to avoid the risk of deleting useful edges…)
I didn’t know selchain command, pretty useful.
(I usually go CTRL+SHIFT + double click, but selchain is more powerful indeed)
Thanks!
But I made a mistake, I should have said that this is for a coded context, no manual input.
I need all and every loops.
Best would be to have this inside c# , rhinocommon… but if it’s a plugin it’s ok…
The script loops over topology edges and finds the 2 connected triangles. It then finds the point on each triangle which is not on the edge. This is the origin to measure the angle of each triangle which should be close to 90 degree. If both triangle corner angles are within tolerance (i used 1.55 degree) it compares the difference between both face normals (0.02 degree) and selects the faces if it stays below normal tolerance.
In a second step you could extract the faces, filter mesh parts eg. if they have only 2 faces. Then from the rest duplicate the borders and split the polylines at the sharp angles which are all close to 90 degree…
