Feature request: Intersection Polyline

[yetigit]

Hi, thank you for your efforts on doing a fast and robust csg lib

what would be a killer feature is being able to retrieve the intersection data, precisely as naturally ordered polyline(s).
which boils down to just having the intersection points in the right order ; with a topological predicate since there can be several intersection loops.

here a sphere vs a cube

cube vs cube

[elalish]

Check out my GetMeshRelation() function. It returns this data (in a different format, suitable for multiple uses like texture mapping), even after a whole series of Boolean operations. It should be pretty simple to convert it to the polyline format you desire; feel free to add a PR!

[hrgdavor]

I am still on the sidelines watching manifold progress, and have used it only a bit, but I am wondering about a thing regarding union and filet.

There is a use case when unioning two shapes to filet the intersection edge like this issue: openscad/openscad#884 ...

Is it possible to get something in that direction by finding the edge after union and using smooth in manifold ?
if possible, it would make for a great example script on monifoldcad web.

[elalish]

Yes, part of why I developed our smoothing algorithms is to eventually enable features like fillet. However, it still needs considerable work: beyond just identifying the intersection edges, you'll also need to create new vertices that represent the edges of the fillet and remove the actual intersection verts. Basically we need a MakeChamfer function first, then from that we can use smoothing to turn the chamfer into a fillet.

[hrgdavor]

@elalish that is great to hear. I am glad you are looking to tackling this eventually :)

[elalish]

If you know anything about chamfer algorithms, I'm all ears. I think that will still be pretty hard.

[hrgdavor]

aah, sorry :) my knowledge is lacking in computational geometry. Best I can do for now is to cheer you :) and hope you can find something workable for chamfer.