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|ID||Project||Category||View Status||Date Submitted||Last Update|
|0003065||PartDesign||Bug||public||2017-06-01 23:08||2018-01-02 17:56|
|Target Version||0.18||Fixed in Version||0.17|
|Summary||0003065: Part::checkIntersection returns false negatives preventing functioning of PDN Mirror transformation when faces just touch|
Part::checkIntersection first uses first_bb.IsOut(second_bb) for a quick test. However, this function is known to fail in cases of touching (there is even a previous comment in the code). Mirror transformation explicitly asks that touching to be considered intersection. Therefore it is wrong to rely on this test.
The Extrema method implemented in Part::checkIntersection fails:
Case 1: When mirroring a feature that just touches, it sometimes fails because BRepExtrema_DistShapeShape returns BRepExtrema_IsVertex instead of BRepExtrema_IsInFace, so the manyfold detection mechanism fails to identify a non-manyfold case. In one example, instead of InFace it returns 4 Vertex: [0, 5.5, -2.5], [0,5.5,2.5], [1E-15, 13, -2.5], [1E-15, 13, 2.5] for Support1 and [0, 5.5, -2.5], [0,5.5,2.5], [-1E-15, 13, -2.5], [-1E-15, 13, 2.5] for Support2. I am unsure if this can be somehow reused.
Case 2: When doing a multitransformation to create a part out of a quarter like here:
The extrema method provides a separation (notable, in the order of milimeters) in operations with intersection parts. This may be a consequence of which parameters we are passing the to function.
Some related problems not directly related to the extrema method, but that seem to be related:
|Steps To Reproduce||EXAMPLE 1|
1. Load the attached file.
2. Activate the first body
3. Select the pad and add a Mirror transformation (you can try directly the mirror, or a multi-transformation, vertical+horizontal to see the different cases)
1. Load the attached file
2. Activate the second body
3. Select the pad and mirror or multi-transform mirror the pad
Helix_Mirror2.fcstd (17,168 bytes)
||@abdullah should this be resolved now that p:FreeCAD:816: has been merged?|
||Yes, this ticket is to be closed as fixed by that PR|
The boolean check method fails in some circumnstances where the extrema method success. For example:
The result is that "the shape does not intersect support" is generated, when the real problem is OCE/OCCT can not make a proper fusion of those valid and perfectly intersecting objects.
IMO it is not ok to inform that something that clearly intersect does not. So this is a bug.
The final outcome in these cases should be: no error because it does intersect, and a resulting bad solid because it is what OCC gives back. This can be solved by a three phase checking (instead of a two phase one):
3. If Extrema says it does not intersect (sometimes because of the non-manifold detection failure), boolean check.
In case of OCC>6.9.0, this checkIntersection, as well as all the fusing in PDN should probably be upgraded to use generalFuse (same as Part boolean fragments fuse).
How about avoiding the check altogether? I.e., mirror, then fuse, then check the result of fusion (it should remain a single solid; if it doesn't -> show the "does not intersect support" message to user).
Another option is to drop the single-solid limitation altogether. Then, the check can also be removed.
Good to hear from you :)
What we have currently in master seems to work well. I am not sure if I "fixed" this, or what exactly went on (I can not remember).
I have just updated the target version to 0.18 to get it out of the 0.17 roadmap, as this is no urgent matter.
I do not close the ticket. I will eventually come back to this and assess it again.
|2017-06-01 23:08||abdullah||New Issue|
|2017-06-01 23:08||abdullah||Status||new => assigned|
|2017-06-01 23:08||abdullah||Assigned To||=> abdullah|
|2017-06-01 23:08||abdullah||File Added: Helix_Mirror2.fcstd|
|2017-06-01 23:08||abdullah||Tag Attached: Mirror transformation|
|2017-06-18 03:49||kkremitzki||Note Added: 0009441|
|2017-06-19 12:49||abdullah||Note Added: 0009454|
|2017-06-19 17:12||Kunda1||Status||assigned => closed|
|2017-06-19 17:12||Kunda1||Resolution||open => fixed|
|2017-06-19 17:12||Kunda1||Fixed in Version||=> 0.17|
|2017-06-19 17:12||Kunda1||Note Added: 0009459|
|2017-06-25 09:36||abdullah||Status||closed => feedback|
|2017-06-25 09:36||abdullah||Resolution||fixed => reopened|
|2017-06-25 09:36||abdullah||Note Added: 0009522|
|2017-06-25 09:36||abdullah||Note Edited: 0009522||View Revisions|
|2017-11-20 10:08||DeepSOIC||Note Added: 0010435|
|2017-11-20 10:10||DeepSOIC||Note Edited: 0010435||View Revisions|
|2018-01-02 17:51||abdullah||Target Version||0.17 => 0.18|
|2018-01-02 17:56||abdullah||Note Added: 0010674|