v.0.18 Sketcher detects redundant constraints vs. v.0.17

[otoien]

When doing the edits sometimes line endpoints get disconnected from each other and it is necessary to connect again by applying a coincident constraint (perhaps that is where you point out that tangency can be applied directly?).

That's exactly how it happens. From a geometric point of view it is no problem to have both, because the coincident point lies on both connected lines and lies thus on a tangent of both. However internally there can rise problems because the points are represented with finite precision.

That's why you should select the endpoints when applying tangency in these cases.

Thanks, I see how it works now (and why I got circles ) , much easier to join the two points directly by applying a tangent. However I just tested and find that the end result will be the same as I could confirm that the coincident constraint is automatically deleted when the tangent is applied. In the following screen capture I had just applied coincidence constraints between the lines and the arc and then selected the line an arc ready do apply tangent. The next screenshot shows how the coincidence constraint is automatically deleted and reported in a message box. Again it is more complicated than needed and your advice is well taken, but it should not cause any ill effects. And if one initially draws a line and an arc so that they coincides (thus a coincident constraint is automatically created), it is good to know that it is removed once the tangent is applied):
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[chrisb]

That's how the Sketcher/Solver works now. If you edit an old model you might still have the old situation.

[otoien]

Thanks, good to know. I also found the detailed page on tangents in the wiki (missed that there was a hyperlink from the constraint overview page before, apologize for that), and see that there is more to how a tangent is selected and interpreted than one would think.

[abdullah]

Thanks, and I have found some other issues concerning selections - which might be worth a new topic, please tell me if you prefer this:

For me it is ok that they are here. Make a bug report on the tracker and point to this post. Something easy like "Problems with selections". Do not lose your time in descriptions, the post already shows the issues. Eventually I will come back to it.

abdullah wrote: ↑
Sat Jul 07, 2018 6:44 am
(and avoid me the effort of going through all the list of equality constraint in the constraint widget and asking for the elements that the equality is constraining).

Which should have been my responsibility. I had forgotten about the extended information where edge number -2 should have raised my suspicion.

It is ok . But it is worth mentioning that I felt the same way when I arrive to constraint80, it is like: why did not I see this suspecting -2 from the beginning and went all the way until constraint80?

[chrisb]

Make a bug report on the tracker and point to this post. Something easy like "Problems with selections". Do not lose your time in descriptions, the post already shows the issues.

Done: issue #3530

Eventually I will come back to it.

[chrisb]

I can reproduce the issue with the warning "Equality constraints between circle and line are not supported."

- Edit new sketch
- create an arc (or a circle).
- select the arc and either X- or Y-axis
- apply equality

-> A constraint is created and the warning is issued in report view.

Finally something funny: I found out how long the X-axis is: Create an equality between X-axis and a line, then the length is 1mm . The same holds of course for the Y axis.

In the first place I must have created this issue in the following way: The Y axis was selected and I was unaware of that. Then I created an equality between arcs. That included the axis as described above.

[chrisb]

Created issue #3532.

[abdullah]

Created issue #3532.

https://github.com/FreeCAD/FreeCAD/pull/1697

[abdullah]

Thanks, and I have found some other issues concerning selections - which might be worth a new topic, please tell me if you prefer this:

• When I select with a rectangle selection I don't get all constraints. In the attached image I have made a rectangle selection and none of the tangents was selected.
  selectRect.png
• when I select a single point it doesn't show in 3D view (it's the point in the middle of the arc)
  Bildschirmfoto 2018-07-07 um 10.16.11.png
• vice versa it's similar: selecting the point in 3D view doesn't show in the list.

Hi!

I had some time to come around your list. For the first two items, the software shows the behaviour intended by the developer, which may or may not be the intended by the user:

- In the case of the box selection, it is designed to ignore constraints.
- In the case of the point selection, I do understand your point, but you have the geometry list configured for edge, so if you try to select the edge of a point, you get nothing. If you change it to starting point (press 'z' as a shortcut while on the list) and you click, you will see the point green in the 3D View. This is also true in the other direction (provided that first point is selected). This was intended, as you can use the geometry widget to select the first point of an element, then the second point of another element, and then apply a constraint to both. Somehow, the list is "four lists" in one, it memorizes the selections of each individual list, so that you can apply all the constraints just from the widget. The idea of the widget was that no matter which problem was there in the 3D view that made you resort to the widget, it simply can be done directly from the widget.

The last in your list, appears to me like a bug and I will dedicate some time, probably today.

EDIT: The last in your original list, which is coincident constraint selection...

[abdullah]

• if I select a coincidence with the rectangle selection it doesn't show in the list. This works vice versa.
  Bildschirmfoto 2018-07-07 um 10.41.58.png

Hi again,

What is happening is this:

1. you cannot select a coincidence constrain in the 3D View, only vertices.
2. when selecting a vertex in the 3D view, the point is selected in the Geometry Widget.
3. when trying to delete a selected vertex, a coincidence on vertex is removed as an aid (as it generally does not make sense to delete vertices of a segment). This only happens with delete. For any other operation the vertex is used.
4. when selecting a coincidence in the Constraint's widget, the top vertex where the concidence is located is selected, as no other thing can be selected. This may create the expectation that by selecting the vertex the constraint should be selected, but you may need this selection as a point.

Let me know what you think