Measurement: Support thickness measurement

[maxwxyz]

Is there an existing issue for this?

• I have searched the existing issues

Problem description

Mentioned here: #9750 (comment)

The new unified measurement tool should support the measurement type thickness to measure the thickness on any given point on an object. The thickness could be calculated using the normal vector dierection of the picking point.

Example from CATIA:

@pierreporte FYI

Full version info

OS: Windows 10 build 19045
Word size of FreeCAD: 64-bit
Version: 0.22.0dev.37063 (Git)
Build type: Release
Branch: main
Hash: 680792030fd664c94829e2c1b78b21788e8d9879
Python 3.11.9, Qt 5.15.13, Coin 4.0.2, Vtk 9.2.6, OCC 7.7.2
Locale: German/Germany (de_DE)
Installed mods: 
  * BIM 2021.12.0
  * CurvedShapes 1.0.9
  * Curves 0.6.35
  * fasteners 0.5.20
  * OpenTheme 2024.4.20
  * OpticsWorkbench 1.0.17
  * sheetmetal 0.4.13

Subproject(s) affected?

Core

Anything else?

Related:

• Measurement: Support of individual picking points for distance #13712

Code of Conduct

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

[tobiasfalk]

It would also be nice if the maximum and minimum Thiknes would be displayed, maybe with a angle to the normal vector

[pierreporte]

@tobiasfalk How would you define minimum and maximum thickness?

[tobiasfalk]

@pierreporte I mean it in two ways, the first st that a non uniform body may has a spot where the thickness is at a minimum and a maximum.(this could be done if a surface is selected)
The second is that the thickness may change depending on the angle and that once again in non uniform body's the Normal Vector could be the maximum(same as the cross section of a cube) or something complete else, there it could be interesting in what ange to the NV the maximum and minimum are.
I understand that this will make it a lot more complicated.

[pierreporte]

I still don’t get what the use case would be.

Thickness analysis would be great though, with the part colored like in FEM to indicate thickness below every point of the surface. This is out of scope of this issue.

[tobiasfalk]

[maxwxyz]

Current issue is meant to get the thickness under the picking point of the surface. So calculate the normal direction at the picking point and follow that direction until another surface of that body is hit.
Min/max/mean could also be a use case (your 1.) but this is fairly complex on curved surfaces. For your point 2. i currently do not see a use case but this could still be measured by picking the individual start/end point as workaround.

[pierreporte]

I think I got it. There are two kind of thicknesses:

1. normal thickness, that is measured by the length of the segment normal to the surface at the selected point;
2. total thickness, that is measured by the length of the smallest segment starting at the selected point and not necessarily normal to the surface.

The first one is the original idea illustrated by @maxwxyz’s pictures. The second one is usually seen with thickness analysis where the part is fully colored with specific shades corresponding to known thicknesses, and where the edges or corners have usually zero thickness. The total thickness is useful for manufacturing because some materials or processes need a minimum thickness (like 3D printing), or constant thickness (like injection molding).

Thus I think that the thickness measurement tool should be split in two: normal and total. As well, a potential thickness analysis feature could allow the user to compute both normal and total thicknesses.