[Problem] Sketcher: no way to add intersection geometry

[pierreporte]

Is there an existing issue for this?

• I have searched the existing issues

Problem description

Sketcher_External only projects selected geometry in the sketch plane. The only intersections it can make are with datum geometry, which is very limited. Intersections in sketches are very useful when working with surfaces and wireframe geometry to build-up features.

I would suggest dropping Sketcher_External from the UI (not from code) and replace it with Sketcher_ProjectExternal as a fixed version (no intersection of datum planes and other reported problems) and Sketcher_IntersectionExternal for the intersections.

Full version info

OS: Ubuntu 23.10 (KDE/plasma)
Word size of FreeCAD: 64-bit
Version: 0.22.0dev.36166 (Git) AppImage
Build type: Release
Branch: main
Hash: a5ea8023a29b6d7bbf1ebd57b5ed31dd27c5947b
Python 3.10.13, Qt 5.15.8, Coin 4.0.2, Vtk 9.2.6, OCC 7.6.3
Locale: French/France (fr_FR)
Installed mods: 
  * CosmeticThread3D
  * TabBar (Disabled)
  * sheetmetal 0.4.0
  * OpenDark 2023.12.1
  * OpenLight 2023.12.17

Subproject(s) affected?

Assembly

Anything else?

No response

Code of Conduct

• I agree to follow this project's Code of Conduct

[TomaszSzt]

Just for your information and from an end user point of view who doesn't look into coding details:

If something like that is what you are looking for, then check the LinkBranch https://github.com/realthunder/FreeCAD

[pierreporte]

I know that the Link branch can do it but it is not the official FreeCAD. The goal isn’t just the feature but official support.

[pierreporte]

@realthunder Could you indicate where this is implemented so that the person willing to implement the feature can get inspiration from your work?

[pierreporte]

Interesting feature: when selected geometry doesn’t intersect with the sketch plane, it could be asked to extend it to compute an intersection. It would be only for easily extendable geometry: planar surfaces (so it isn’t necessary to add a datum plane), straight edges (so no datum line necessary). Surfaces fully normal to the sketch plane could also be extended but it would be equivalent to a projection.

@maxwxyz

[realthunder]

It is very difficult to isolate this function in my branch. It is interwind with topo naming code I added to Sketcher. I would say wait until topo naming code is merged. External geometry is not reliable without it anyway.