SVG cannot be converted to a sketch

[chrisb]

As follow-up to https://forum.freecadweb.org/viewtopic.php?f=3&t=50956 I have here an svg file, which was made in Inkscape 1.1. The imported geometry cannot be converted into a sketch. The file contains a circle and nothing else.

To reproduce
- open or import the attached file with mode "SVG as geometry"
- switch to Draft workbench
- select the imported geometry
- apply DraftToSketch

The path is not converted, error message:

Code: Select all

00:15:02  Traceback (most recent call last):
  File "/Users/cb/Desktop/FreeCAD.app/Contents/Resources/Mod/Draft/draftutils/todo.py", line 167, in doTasks
    Gui.doCommand(string)
  File "<string>", line 1, in <module>
  File "/Users/cb/Desktop/FreeCAD.app/Contents/Resources/Mod/Draft/draftmake/make_sketch.py", line 93, in make_sketch
    if not DraftGeomUtils.isPlanar(shape):
  File "/Users/cb/Desktop/FreeCAD.app/Contents/Resources/Mod/Draft/draftgeoutils/geometry.py", line 280, in isPlanar
    n = getNormal(shape)
  File "/Users/cb/Desktop/FreeCAD.app/Contents/Resources/Mod/Draft/draftgeoutils/geometry.py", line 235, in getNormal
    n = getSplineNormal(shape.Edges[0])
  File "/Users/cb/Desktop/FreeCAD.app/Contents/Resources/Mod/Draft/draftgeoutils/geometry.py", line 209, in getSplineNormal
    n.normalize()
Base.FreeCADError: Cannot normalize null vector

00:15:02  ToDo.doTasks, Unexpected error:
<class 'Base.FreeCADError'>
in ['obj0 = Draft.makeSketch(FreeCAD.ActiveDocument.path23, autoconstraints=True)', 'FreeCAD.ActiveDocument.recompute()']

OS: macOS 10.15
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.22611 (Git)
Build type: Release
Branch: master
Hash: 7eeec7a5990cc786723225ca8de16ca3186545b3
Python version: 3.8.5
Qt version: 5.12.9
Coin version: 4.0.0
OCC version: 7.4.0
Locale: C/Default (C)

[Kunda1]

I can reproduce on

Code: Select all

OS: Manjaro Linux (KDE//usr/share/xsessions/plasma)
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.22665 (Git) AppImage
Build type: Release
Branch: master
Hash: b0d7850406e046f3b7a8cd5da261e7d54df6bd99
Python version: 3.8.6
Qt version: 5.12.9
Coin version: 4.0.0
OCC version: 7.4.0
Locale: English/United States (en_US)

Code: Select all

18:22:34  ----------------
18:22:34  GuiCommand: Convert Draft/Sketch
18:22:34  Traceback (most recent call last):
  File "/tmp/.mount_FreeCAIAOwRJ/usr/Mod/Draft/draftutils/todo.py", line 167, in doTasks
    Gui.doCommand(string)
  File "<string>", line 1, in <module>
  File "/tmp/.mount_FreeCAIAOwRJ/usr/Mod/Draft/draftmake/make_sketch.py", line 93, in make_sketch
    if not DraftGeomUtils.isPlanar(shape):
  File "/tmp/.mount_FreeCAIAOwRJ/usr/Mod/Draft/draftgeoutils/geometry.py", line 280, in isPlanar
    n = getNormal(shape)
  File "/tmp/.mount_FreeCAIAOwRJ/usr/Mod/Draft/draftgeoutils/geometry.py", line 235, in getNormal
    n = getSplineNormal(shape.Edges[0])
  File "/tmp/.mount_FreeCAIAOwRJ/usr/Mod/Draft/draftgeoutils/geometry.py", line 209, in getSplineNormal
    n.normalize()
Base.FreeCADError: Cannot normalize null vector

18:22:34  ToDo.doTasks, Unexpected error:
<class 'Base.FreeCADError'>
in ['obj0 = Draft.makeSketch(FreeCAD.ActiveDocument.path23, autoconstraints=True)', 'FreeCAD.ActiveDocument.recompute()']

[vocx]

...
- apply DraftToSketch
...

This is a known issue. See Improvements in SVG. The first post has a summary of various issues with SVG.

Unfortunately the code is broken since February or so, when Yorik and Wandererfan each made changes to DraftGeomUtils.py. I think I can revert the changes, but that may break some code in Arch_CurtainWall (or maybe not, somebody needs to test!).

There may be another solution altogether in the importSVG.py module, as mentioned in that thread by mikeprice99.

[chrisb]

It's indeed the same issue, only my testfile is much simpler. Is there already a ticket?

[Chris_G]

The getSplineNormal cannot work for closed edges.
This would be more reliable :

Code: Select all

def getSplineNormal(edge):
    """Find the normal of a BSpline edge."""
    points = edge.discretize(4)
    v1 = points[1] - points[0]
    v2 = points[1] - points[2]
    n = v1.cross(v2)
    if n.Length:
        return n
    return None

But straight splines would still need to get a special treatment.

[vocx]

It's indeed the same issue, only my testfile is much simpler. Is there already a ticket?

I did not open a ticket about it because I've had it in my mind for a long time; I opened the thread above precisely to document these issues. Besides, it's not like we have a ton of Draft programmers who can address these tickets. If Yorik doesn't fix it, I'll probably try fixing it at some point.

However, by looking at Kunda's thread (Bugs/Issues Blocking v0.19 Release), I notice that it is issue #4416.

This is one of those problems that I would really like to offer as a bounty. We could offer $500 to somebody to go through the entire SVG code, fix issues, and prepare unit tests, so that regressions can be detected more easily.

[chrisb]

This is one of those problems that I would really like to offer as a bounty.

I wouldn't limit it to this issue, although I see your personal interest . We should discuss this in Kunda's topic.

[marioalexis]

This changes solve the problem: https://github.com/FreeCAD/FreeCAD/pull/3954
This can be marked as solved too: https://tracker.freecadweb.org/view.php?id=4416

[chrisb]

Thanks! I really like to see things fixed from the 0.19-blocking list.

[marioalexis]

You are welcome.
Just in case, if something goes wrong with the coplanarity test, there is a tolerance parameter in the make_sketch function, the default value of which should be permissive enough.