How to draw curved arrow easily

ROOT
1

Hi:

I want to represent something like rotation counter-clockwise in my graph. However I can not find any example about curved arrow in all root reference. Right now, an idea come up in my mind is to combine TArrow and TEllipse togethger. But I have to calculate center and two radius of ellipse and end point of ellipse sector as well as the tangent line across the the end point of ellipse sector to make sure the arrow points to correct direction. That is too cumbersome. Is there an easier way to do that? I means just like the constructor of TArrow, but a more parameter to control concave or convex.

2

Hi,

could a solution which implies drawing an image and not a ROOT graphics primitive be viable?
See for example Inserting logo or image

D

3

Yes, ROOT arrows have a straight body. Can you point to some picture showing what you would like ?
We may try to produce the “cumbersome” math you are talking about…

4

First example: just pay attention to the red curved arrow
https://en.wikipedia.org/wiki/Moment_of_inertia#/media/File:Moment_of_inertia_rod_center.svg

Second example:

rotation.png1600×1200 23.4 KB


pay attention on the curved arrow above theta

5

I see. I confirm ROOT does not have this kind of arrows. That’s something we could add. First I would say that a simple macro would be enough, Then we could see, on the long term, to include it in TArrow or TEllipse.

6

Hi!! I also need this kind of curved shaped arrow. Any news in addition of this kind of feature in latest version of root??

7

No, nothing new. You can do it with two primitives: One arc of circle and an arrow.