How to get the absolute rotation of a Node in JavaFX

Question

In JavaFX the rotateProperty of a Node provides me with its rotation in degree relative to its parent. Is there a way to get the absolute rotation in degree, either relative to the Scene or the Screen?

For example, is there a way to calculate the angle from the Transform object of a Node i can get from getLocalToSceneTransform()?

Answer 1

So, i did the math myself, and for my case i either get the rotation in Radians via:

double xx = myNode.getLocalToSceneTransform().getMxx();
double xy = myNode.getLocalToSceneTransform().getMxy();
double angle = Math.atan2(-xy, xx);

or

double yx = myNode.getLocalToSceneTransform().getMyx();
double yy = myNode.getLocalToSceneTransform().getMyy();
double angle = Math.atan2(yx, yy);

In both cases this can be converted to 360-degrees:

angle = Math.toDegrees(angle);
angle = angle < 0 ? angle + 360 : angle;

Answer 2

The question isn't really well defined, since different Nodes in the Scene graph are potentially rotated about different axes.

The getLocalToSceneTransform() method will return a Transform representing the transformation from the local coordinate system for the node to the coordinate system for the Scene. This is an affine transformation; you can extract a 3x4 matrix representation of it relative to the x- y- and z-axes if you like.