Part.Loft - Wrong Vertices Linked?

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wandererfan
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Re: Part.Loft - Wrong Vertices Linked?

Postby wandererfan » Wed Apr 09, 2014 1:07 am

wmayer wrote:The reason for the failure has to do with the placement applied on the sketches because I assume the internal orientation of the shapes doesn't fit to what the loft needs. All three sketches have totally different rotation axes and this might be the major problem.
This is "orientation" as a geometric concept, not "Orientation" as a property of Wires/Edges, correct?
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wandererfan
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Re: Part.Loft - Wrong Vertices Linked?

Postby wandererfan » Wed Apr 09, 2014 1:38 am

wmayer wrote:As a quick test I copied the sketches into a new document and reset the placements. Then for sketch two I set rotation axis=(0,1,0) angle=90 deg and for sketch three the same axis and angle=180 deg. So, this gives the same form (but in a different position of course) and the the loft works as expected.
I extended your test to a circular loft using the double sketch hack to force the closure.
CircleLoftPlacement.png
CircleLoftPlacement.png (12.73 KiB) Viewed 1200 times
In the previous attempt I drew the sketches on the appropriate plane (XZ or YZ, possibly "reverse direction" where appropriate) and used distance and symmetry constraints to position them. I didn't adjust Placements manually.

Are the resulting complicated Placements an indication of poor technique or a bug in Sketcher/Part Design or ??
Attachments
CircleLoftPlacement.fcstd
(7.27 KiB) Downloaded 32 times
jmaustpc
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Re: Part.Loft - Wrong Vertices Linked?

Postby jmaustpc » Wed Apr 09, 2014 4:39 am

By the way, I tried "Part Reverse shape" on that central sketch, where the twist came in, when I first tried it, it made no difference.

Are the two different versions of OCC dealing with this differently, as the older OCC (even with the same latest FreeCAD) seemed to work for me.
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wandererfan
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Re: Part.Loft - Wrong Vertices Linked?

Postby wandererfan » Wed Apr 09, 2014 11:28 am

jmaustpc wrote:Are the two different versions of OCC dealing with this differently, as the older OCC (even with the same latest FreeCAD) seemed to work for me.
I try to keep my relationship with OCC on a strictly blackbox basis if at all possible. :cry: I'll see if I can find a change log for ...ThruSections, but the change, if it exists, could be anywhere.

A DRAWEXE script that illustrates our issue might help, but I don't really know how to use this to create specific OCC test cases that mimic FC issues.
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wandererfan
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Re: Part.Loft - Wrong Vertices Linked?

Postby wandererfan » Thu Apr 10, 2014 12:12 pm

jmaustpc wrote:By the way, I tried "Part Reverse shape" on that central sketch, where the twist came in, when I first tried it, it made no difference.
Yeah, I made an experimental version that allowed each profile to be reversed independently, and could find no combination of reversed/forward that made any difference. :oops:

Seems "Reverse" on a wire relates to what's inside/outside the closed curve. It doesn't really refer to the direction of circumnavigation, and this problem seems to be related to the direction of circumnavigation of the profile as viewed in the direction of the loft "path".

More digging required. :(

wf