Arch-Section cuts 1mm to high and ignores selection

[HoWil]

Hello,
I recently use/evaluate Arch-section as a tool to cut 3D-Objets, mainly boolean-fragmenst, to make inner boundaries and solids accessible for selection for FEM. I encountered some strange behaviour which I want to report here:
* The Arch section is cut 1 mm to high. This is for Arch specific topics meaningless but if one wants to use it in e.g. FEM than 1 mm sometimes can be really large. In the attached model I cut a boolean-fragments part consisting of 3 spheres. All spheres are centered around z=0. The Arch-section is also set to z=0 but it cuts on z=1mm. Please see the attached screenshot:

Bildschirmfoto von »2018-05-11 21-44-49«.png (285.55 KiB) Viewed 1106 times

* Arch-Section shows a selection-field called 'Objects' which unfortunately is ignored. All Objects in the model are cut. In the attached model is 'Kegel' (Cone) also cut even if only 'BooleanFragments' was selected.

* The position of the section and the cut objects are not updated when I directly insert values into the 'Position' subsections for x,y and z. This is different when I e.g. change the position vales with "key-up" or "key-down". But mostly I have to update the view with disabling "Cut-view" and enabling it back again in View-Tab. Maybe a double-click could be used to enable and disable the cut.

I used:
OS: Ubuntu 16.04.4 LTS
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.18.13674 (Git)
Build type: None
Branch: master
Hash: 32f089f28408479ce65a22a753bb815ffe3d45ed
Python version: 2.7.12
Qt version: 4.8.7
Coin version: 4.0.0a
OCC version: 7.2.0
Locale: German/Austria (de_AT)

but 0.7 behaves the same.
BR,
HoWil

[paullee]

Hello,
I recently use/evaluate Arch-section as a tool to cut 3D-Objets, mainly boolean-fragmenst, to make inner boundaries and solids accessible for selection for FEM. I encountered some strange behaviour which I want to report here:
* The Arch section is cut 1 mm to high. This is for Arch specific topics meaningless but if one wants to use it in e.g. FEM than 1 mm sometimes can be really large. In the attached model I cut a boolean-fragments part consisting of 3 spheres. All spheres are centered around z=0. The Arch-section is also set to z=0 but it cuts on z=1mm. Please see the attached screenshot:

Bildschirmfoto von »2018-05-11 21-44-49«.png

* Arch-Section shows a selection-field called 'Objects' which unfortunately is ignored. All Objects in the model are cut. In the attached model is 'Kegel' (Cone) also cut even if only 'BooleanFragments' was selected.

* The position of the section and the cut objects are not updated when I directly insert values into the 'Position' subsections for x,y and z. This is different when I e.g. change the position vales with "key-up" or "key-down". But mostly I have to update the view with disabling "Cut-view" and enabling it back again in View-Tab. Maybe a double-click could be used to enable and disable the cut.

Before Yorik or others provide more helps...
... somehow something about the Arch Section Plane was discussed (off-topic!) here...
https://forum.freecadweb.org/viewtopic. ... 30#p185612

- surprise to know it is 1mm above to work
- The Objects works with Shape2DView, and with Drawings / TechDraw....
- The Cut is more or less the Clipping Plane on all objects in the documents...
... ( suggested in the above 'off-topic' discussion to have option to work on selected "Objects" only)
- wiki has more information https://www.freecadweb.org/wiki/Arch_SectionPlane

EDIT:
- you may use Regis's technique to add a Shape2DView right at the cut plane ... (follow his comments)
- then, you are a shape cut at the plane to select, snap .... (not know if it work for non-Arch Object)
- BUT, do not know (if) it is 1mm off??

[FATHI RAMMAH]

Hello,
I recently use/evaluate Arch-section as a tool to cut 3D-Objets, mainly boolean-fragmenst, to make inner boundaries and solids accessible for selection for FEM. I encountered some strange behaviour which I want to report here:
* The Arch section is cut 1 mm to high. This is for Arch specific topics meaningless but if one wants to use it in e.g. FEM than 1 mm sometimes can be really large. In the attached model I cut a boolean-fragments part consisting of 3 spheres. All spheres are centered around z=0. The Arch-section is also set to z=0 but it cuts on z=1mm. Please see the attached screenshot:Bildschirmfoto von »2018-05-11 21-44-49«.png


* Arch-Section shows a selection-field called 'Objects' which unfortunately is ignored. All Objects in the model are cut. In the attached model is 'Kegel' (Cone) also cut even if only 'BooleanFragments' was selected.

* The position of the section and the cut objects are not updated when I directly insert values into the 'Position' subsections for x,y and z. This is different when I e.g. change the position vales with "key-up" or "key-down". But mostly I have to update the view with disabling "Cut-view" and enabling it back again in View-Tab. Maybe a double-click could be used to enable and disable the cut.

I used:
OS: Ubuntu 16.04.4 LTS
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.18.13674 (Git)
Build type: None
Branch: master
Hash: 32f089f28408479ce65a22a753bb815ffe3d45ed
Python version: 2.7.12
Qt version: 4.8.7
Coin version: 4.0.0a
OCC version: 7.2.0
Locale: German/Austria (de_AT)

but 0.7 behaves the same.
BR,
HoWil

Hi ,by logic the section plane has no thickness and when it work with architectural stuff it must be jumped at least 1 mm above the 0 z axis to be able make section of the arch objects which usually have thickness more 1 m , so to solve this problem you must change the Z position to - 1 mm and back it again to zero.

[yorik]

The reason the cut is done 1mm above the actual cut plane is so objects that are exactly lying on the cut plane still appear, including the cut plane itself. But we could make that distance a user-changeable property...

[HoWil]

... so to solve this problem you must change the Z position to - 1 mm and back it again to zero.

Thanks for your answer, but unfortunately this is not reproducible. For me it looks like the view is only refreshed at each second change (mouse-wheel scroll in the field of the placement-value. This is confirmed by your screenshot which shows the spheres clipped at -1mm.
BR,
HoWil

[HoWil]

The reason the cut is done 1mm above the actual cut plane is so objects that are exactly lying on the cut plane still appear, including the cut plane itself. But we could make that distance a user-changeable property...

Sounds great!
BR,
HoWil

[yorik]

Done in git commit ea0df1e21