Trim curve based on radius of control points using geometry nodes

Question

I am trying to trim straight curves (actually converted from mesh edges) so that each endpoint is trimmed by half the value of its radius — so that if I succeeded, the new trimmed endpoints would be at the limits of cubes placed at the old untrimmed endpoints, each cube having the size of the radius of one of the old endpoints (somewhat like if the cubes were used to cut the curve using a boolean modifier). Unfortunately I haven’t found yet how to achieve that, the example file shows one of my various attempts.

On this screenshot the left cube size is 1, the right cube size 0.5, the curve left control point has a radius of 1, the right control point has a radius of 0.5. So I would expect the curve left end to be trimmed by 0.5 and the right end by 0.25.

That is a simplification to isolate my issue to submit here, but actually in various abstract geometric artworks I am currently designing https://skfb.ly/oMEUU lots of cube and curves are generated from the points and edges of a mesh, by a far more complicated geometry nodes setting with a variable radius field in order to create tubes of square section with cubes at intersections and turns.

Answer 1

In this particular case, I would not use the Trim Curve node if I were you, for two reasons:

1. When trimming, the values for the radii are interpolated, so you end up with incorrect values for Curve to Mesh.
2. You cannot create sections with it, you can only move the end points.

Therefore, I would suggest the following solution:

First split the edges so that you get individual segments. Before that, you capture the index of the points so that you can restore the radii after splitting.

Then simply move the respective end points along the tangents (or in the opposite direction) by the required value. In this way, you should be able to achieve the desired result even with continuous lines.

_{(Blender 4.0+)}