[ Fixed ] [ Ticket #4144 ] Sketcher: Point-point-point symmetry: order of points?

[openBrain]

In either scenario (selecting the tool first or the geometry first), the resulting input to the software is the same (two points and a line). The most user-friendly approach would be to have the order not matter - the user selects the geometry in any order and the software intelligently sorts things out. Even if you prefer one order over another, you'd get what you want with this approach. Win, win, win.

Seriously ? Read the thread title again. And the thread also...
The whole point is about the point-point-point symmetry.

[wmayer]

If I click the tool first the required order is:
PtA-Center-PtB
If I click the tool last the required order is:
PtA-PtB-Center

Why is the point order different?

I told the guy who developed the possibility to make the selection after the symmetry tool is started that it's inconsistent to the way when the selection is made beforehand. He didn't care and did it on purpose.

In either scenario (selecting the tool first or the geometry first), the resulting input to the software is the same (two points and a line). The most user-friendly approach would be to have the order not matter - the user selects the geometry in any order and the software intelligently sorts things out. Even if you prefer one order over another, you'd get what you want with this approach. Win, win, win

In general this is not possible. Just consider the case where you select three points that are not collinear but form a triangle -- especially when it's an equilateral triangle. Then you have three possibilities how to do the symmetry.

[wieszak17]

Maybe just simple rule: out of three points, point at which angle is biggest in this triangle is a symmetry point. No check for equality of angles - in this case user need to move one of the points to make situation clear.

[GeneFC]

Maybe just simple rule:

There are guaranteed to be user exceptions to every auto-generated rule. It would be good to declare a single required order for manual selection and be done with it.

Does not matter which order for me; I can learn either.

Gene

[chrisb]

Where is the big deal in selecting the points in the sequence as requested now? It is clear and well defined. That's much easier than select points - apply symmetry - (wrong!) - undo - move one of the points - select points again - apply symmetry again.

[rogermhsu]

No. The topic is about point-point-point symmetry. But there has been another discussion and even a vote about PPP symmetry.
Found it:
https://forum.freecadweb.org/viewtopic.php?f=3&t=45257

Oh, whoops, don't know how I missed the point-point-point part. My bad!

Thanks for the other link; I'll check it out.

[Pauvres_honteux]

I'm curious about what happens after you've created this symmetry and then change one of the points position?
Could there be one/several case/cases where the symmetrical point gets flipped?

Maybe a GUI element indicating the symmetry axle could be implemented so us users clearly can see what was/is used as symmetry axle?
Preferable an icon in the tree as well. E.g. sub branch the symmetry icon.
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Symmetry_in_sketcher.png (62 KiB) Viewed 756 times

[Roy_043]

@Pauvres_honteux:

1. "Could there be ... cases where the symmetrical point gets flipped?" Of course.
2. You suggestion regarding the tree seems peculiar as none of the other elements in a sketch are listed in the tree. Using "Original Point 1" and "Symmetry of Point 1" would be confusing as no objects are copied.
3. A symmetry point may be the original point for another symmetrical constraint.
4. Also a symmetry point need not be a point object, it could f.e be the endpoint of a line.