# Flipping by Axis + Rotation of an Arc and an Elliptical Arc

Issue #829 resolved
Ronan Le Tiec created an issue

I'm not entirely sure if it's a bug.

I create an arc and an elliptical arc. The curve is for both in the same direction.

When I flip them by axis, they have opposite direction.

If I then rotate the flipped arc and elliptical arc, they rotate in opposite direction.

Attached is the test val file and 2 screenshots.

1. reporter

A question regarding the rotation / flipping axis etc, why is it not possible to rotate / flip lines?

2. repo owner

A question regarding the rotation / flipping axis etc, why is it not possible to rotate / flip lines?

For many reasons i decided not to allow these operations for lines. First of all in many cases line bounded to points, there is no real line you can rotate. Plus line always must have points, always. Lines are not important for the tool Seam Allowance, they are primarily for humans. Remember what i said about a line? It must always have two points. Imagine a case №1, you rotate point at the end of line. Because you have selected only one point, rotated line doesn't have a start point. Question, how to describe it in this case? Because we should provide a user with information about it: length and angle. Imagine a case №2, you want rotate a tool line. This case even worse, no points at all. Yes, this is possible to rotate an object on scene, but such a line cannot have any name and parameters.

3. repo owner
• changed status to open

Confirm rotation bug for Elliptical Arc.

4. repo owner

Fixed issue #829. Flipping by Axis + Rotation of an Arc and an Elliptical Arc.

→ <<cset 477a6245cca8>>

5. reporter

For many reasons i decided not to allow these operations for lines.

Ok I understand, it all makes sense. A curve also needs two points, why isn't it a problem as well?

Why is the direction of the Arc and the Elliptical arc opposite after axis flipping? See 1_step.jpg . It probably doesn't matter that much, i'm just wondering from a geometrical point of view.

6. repo owner

A curve also needs two points, why isn't it a problem as well?

Because we use poore lines. Lines right now are rudimental. There is no object that contain information about a line. Curves do have such an object.

Okay, if you feel like you miss this feature you could try to implement it. Maybe you see what i don't.

7. repo owner

Why is the direction of the Arc and the Elliptical arc opposite after axis flipping? See 1_step.jpg . It probably doesn't matter that much, i'm just wondering from a geometrical point of view.

Because it is a mirror image.

8. reporter

Okay, if you feel like you miss this feature you could try to implement it. Maybe you see what i don't.

That could be something to do in the future, but it's probably not to important now. I'm not really missing it, I try to understand the difference and you just explained it well, so it's fine by me.

Because it is a mirror image.

That's my problem, if you look at the green arcs, they both go to direction bottom, but if you look at the mirror image, the pink ones, then one goes up und one goes down. For me it's not a correct mirror image.

9. repo owner

Correct an arc direction after flipping. ref #829.

→ <<cset 214afcc85ce3>>

10. repo owner

My last change may cause broking patterns if they affected by this bug.