lofts with solid objects as base are invisible

[Vincent B]

There are a small bug with loft (partDesign). select the face and lunch loft. Choose the sketch as second section: nothing carried out.
Re open the task box, the loft works but still not follow a sketch dimension change.
...
OS: Windows 10 (10.0)
Word size of FreeCAD: 64-bit
Version: 0.20.25943 (Git)
Build type: Release
Branch: master
Hash: a65464b722a846bd2999aa2fecdff1132b15b297
Python version: 3.8.12
Qt version: 5.12.9
Coin version: 4.0.0
OCC version: 7.5.2
Locale: French/France (fr_FR)

[Shalmeneser]

If I select the face, launch loft, select the sketch : the job is done but no previsualization nor visualization.
I need after to space-bar the loft.

It works better if : select the face, select the sketch, launch loft. There is previsualization then visualization.

Code: Select all

OS: Linux Mint 20.2 (MATE/mate)
Word size of FreeCAD: 64-bit
Version: 0.20.26202 (Git) AppImage
Build type: Release
Branch: master
Hash: ca6d49d080dea0abc23d954743eca7c46f33469b
Python version: 3.9.7
Qt version: 5.12.9
Coin version: 4.0.0
OCC version: 7.5.3
Locale: French/France (fr_FR)

[drmacro]

Confirmed; not visible until space bar.

Snip macro screenshot-86d9b9.png (48.08 KiB) Viewed 1884 times

OS: Debian GNU/Linux 10 (buster) (XFCE/lightdm-xsession)
Word size of FreeCAD: 64-bit
Version: 0.20.26230 (Git)
Build type: Release
Branch: master
Hash: cd91c73382ad078f1857296faeef1f97f71b9e61
Python version: 3.7.3
Qt version: 5.11.3
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: English/UnitedStates (en_US)

[TheMarkster]

Some results I have found with this version:

OS: Windows 10 (10.0)
Word size of FreeCAD: 64-bit
Version: 0.20.25997 (Git)
Build type: Release
Branch: master
Hash: 77b198048a63f1e9ca15eef64c8042d599a14cf3
Python version: 3.8.12
Qt version: 5.12.9
Coin version: 4.0.0
OCC version: 7.5.2
Locale: English/United States (en_US)


Select box face in 3D view, then select edge of sketch, then launch loft -> works as expected, complete with preview.

Select box face in 3D view, then select sketch in tree, then launch loft -> works as expected, complete with preview.

Select box face in 3D view, then launch loft, then add section, select edge of sketch -> works, but no preview and you must toggle loft visibility off and back on.

Select box face in 3D view, then launch loft, then add section, then switch to tree view and select sketch from tree, return to task, no preview, press Ok -> works, but you must again toggle loft visibility off and back on to see the result.

Note: When toggling visibility is required the loft icon shows itself to be visible in the tree, but is not visible in the 3D view. If you toggle it invisible the icon still shows as visible, then toggle back to visible and it works as expected afterwards.

[openBrain]

Some other bits of information :
* Forcing document recomputing changes nothing to the problem
* The problem doesn't exist using sketch as a base profile => Due to using a face as base
* The problem also exists if the base face is from a Pad => Not due to using a primitive
* Notice that you can Loft from face to sketch, but not from sketch to face !

So first, is FreeCAD supposed to support lofting from face at this moment ?

[jnxd]

Can confirm loft doesn't behave as expected on the following (ignore the branch, just something I had compiled):

OS: Ubuntu 20.04.3 LTS (MATE/mate)
Word size of FreeCAD: 64-bit
Version: 0.20.26203 (Git)
Build type: Unknown
Branch: fem-constraint-qol
Hash: 3a5c5576ea269b8bae14325db844e4d9201a7fa4
Python version: 3.8.10
Qt version: 5.12.8
Coin version: 4.0.0
OCC version: 7.5.2
Locale: English/United States (en_US)

Could someone who has tested it well enough report it in the tracker? I'll take a look when I can.

[TheMarkster]

Some other bits of information :
* Forcing document recomputing changes nothing to the problem
* The problem doesn't exist using sketch as a base profile => Due to using a face as base
* The problem also exists if the base face is from a Pad => Not due to using a primitive
* Notice that you can Loft from face to sketch, but not from sketch to face !

So first, is FreeCAD supposed to support lofting from face at this moment ?

The reason you can loft from a face is the Profile property is of type App::PropertyLinkSub, which allows for subobjects, like Faces and Wires to be used. But the Sections property is not App::PropertyLinkSubList, it is type App::PropertyLinkList, which does not support subobjects. The Sections objects must all be 2D objects, like sketches or perhaps Faces or Wires would also work. (As an aside, Edges and Vertex objects are not allowed as Profile subobjects, but I don't think this limitation is strictly necessary because these can form solids when lofted to wires.)

[jnxd]

Been at this for a couple of days trying to figure out the parts where visibility is controlled. So far only successful in making the loft "temporarily visible" when we start loft with just the profile (the first section) selected (PR #5147).

However, for some reason, when we start with a solid's face as a profile and a new section is added, only the loft until the previous sections is visible on pressing OK. Toggling visibility off and on shows the new loft.

[uwestoehr]

However, for some reason, when we start with a solid's face as a profile and a new section is added, only the loft until the previous sections is visible on pressing OK. Toggling visibility off and on shows the new loft.

Yes, the PR does not fix the problem completely. I could not yet figure out why a recompute does not help, only a visibility toggle.

[uwestoehr]

The problem is somewhere deeper. It turned out that the box alone causes a visibility issue. Here a recipe to reproduce:

take this example file:

loftbug.FCStd

(13.02 KiB) Downloaded 35 times

- select the SketchBase in the tree
- create a loft and select the circle as section
- press OK to close the dialog

result: the loft is invisible, toggling the visibility only toggles the box, the loft is never shown

- now repeat the loft creation, but delete the box before you start
result: now everything works fine

So despite the box is not part of the loft, it affects it.