Swapped edges on loft

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PaulC
Posts: 7
Joined: Wed Apr 08, 2015 7:25 am

Swapped edges on loft

Postby PaulC » Sun Jan 24, 2016 8:47 pm

Hi all,

Just working through some exercises to learn Freecad. I have some strange behaviour on a loft I was trying between 3 rectangles, the left hand loft seems to have swapped the edges over. I've tried redrawing the rectangles and changing the order of the loft, but I still get similar results? Any one got any ideas?

Here's the FreeCAD info:-

OS: Windows 10
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.15.4671 (Git)
Branch: releases/FreeCAD-0-15
Hash: 244b3aef360841646cbfe80a1b225c8b39c8380c
Python version: 2.7.8
Qt version: 4.8.6
Coin version: 4.0.0a
OCC version: 6.8.0.oce-0.17

File attached.

Thanks,
PaulC.
Attachments
Loft_3.jpg
Screen Shot of Loft
Loft_3.jpg (18.46 KiB) Viewed 1050 times
Loft_3.FCStd
(6.01 KiB) Downloaded 26 times
Joyas
Posts: 482
Joined: Sat Jul 12, 2014 8:39 pm

Re: Swapped edges on loft

Postby Joyas » Mon Jan 25, 2016 12:59 am

If you can use more rectangles, It could be fixed.
I prefer JavaScript, I don't like Python indentation.
User avatar
bejant
Posts: 5934
Joined: Thu Jul 11, 2013 3:06 pm

Re: Swapped edges on loft

Postby bejant » Mon Jan 25, 2016 2:58 pm

Hi PaulC, and welcome. You can also make another Sketch of a 180 degree arc, and use Sweep instead:
20160125b.png
20160125b.png (15.94 KiB) Viewed 1012 times
20160125b-Loft_3.FCStd
(18.41 KiB) Downloaded 9 times
Your FreeCAD version is pretty old, if it doesn't work for you, you'll have to upgrade. It worked for me using:

OS: Ubuntu 14.04.3 LTS
Word size of OS: 32-bit
Word size of FreeCAD: 32-bit
Version: 0.16.6272 (Git)
Build type: None
Branch: master
Hash: 57fadb1663ff668fa8e91f5629b55870476f4d8b
Python version: 2.7.6
Qt version: 4.8.6
Coin version: 4.0.0a
OCC version: 6.8.0.oce-0.17
PaulC
Posts: 7
Joined: Wed Apr 08, 2015 7:25 am

Re: Swapped edges on loft

Postby PaulC » Thu Jan 28, 2016 10:43 am

Thanks very much for the comments and the suggestions. My original task was to create a door handle with varying geometry, how ever I'm beginning to wonder if Loft is the correct operation..... I take your point bejant!

I've redraw the model with alot more sections to help the loft, but I'm still getting the strange behaviour at the end of the loft eg. the edges are swapped at the end of the loft, also if the look at the beginning of the loft there's an indent?

Here's the results:-
Attachments
Loft_5.FCStd
(68.04 KiB) Downloaded 14 times
Loft_5.jpg
Loft_5.jpg (26.5 KiB) Viewed 986 times
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bejant
Posts: 5934
Joined: Thu Jul 11, 2013 3:06 pm

Re: Swapped edges on loft

Postby bejant » Thu Jan 28, 2016 11:49 am

I'm getting the same problem, and also your original Loft fails Check Geometry with BOPCheck enabled. It looks like the best, and maybe only, way to get the desired results is to make another Sketch of a 180 degree arc and use it as the Sweep Path instead. Using a Sweep also fixes the unwanted indent between Sketches F1 and F2, and the resulting Sweep is valid.
PaulC
Posts: 7
Joined: Wed Apr 08, 2015 7:25 am

Re: Swapped edges on loft

Postby PaulC » Thu Jan 28, 2016 1:07 pm

OK, that's interesting. I think I'll try a sweep instead. Do you think it's a bug in the Loft function? or am I asking too much from Loft?
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DeepSOIC
Posts: 7052
Joined: Fri Aug 29, 2014 12:45 am
Location: Saint-Petersburg, Russia

Re: Swapped edges on loft

Postby DeepSOIC » Thu Jan 28, 2016 1:21 pm

Looks like a bug indeed. Maybe the orientation of the sketch matters (try ticking reversed checkbox when asked for sketch plane). I haven't really investigated this, yet...
PaulC
Posts: 7
Joined: Wed Apr 08, 2015 7:25 am

Re: Swapped edges on loft

Postby PaulC » Thu Jan 28, 2016 2:50 pm

Hi DeepSOIC, I'll try a slightly simpler example with the planes reversed, as I've had the swapped edges on all my examples so far.
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bejant
Posts: 5934
Joined: Thu Jul 11, 2013 3:06 pm

Re: Swapped edges on loft

Postby bejant » Thu Jan 28, 2016 5:29 pm

DeepSOIC wrote:Looks like a bug indeed. Maybe the orientation of the sketch matters
Interesting...I think you're on to something. When I went to edit that last Sketch (F15? - going from memory here) the view flipped around the other way, opposite all the others opened.

But I also copied the Sketch "F1" and moved the copy over to where F15 is, and used the copy as the last Sketch in the Loft, and it didn't help...
PaulC
Posts: 7
Joined: Wed Apr 08, 2015 7:25 am

Re: Swapped edges on loft

Postby PaulC » Thu Jan 28, 2016 11:37 pm

Sketch with reversed plane checked, doesn't seems to matter, still strange results.
Attachments
Loft_6.FCStd
(19.44 KiB) Downloaded 9 times
Loft_6.jpg
Loft_6.jpg (22.5 KiB) Viewed 925 times