In Cesium.Shapes there is a static function named "computeEllipseBoundary". One of the params it takes is "rotation". I understand what this value is, but I'm not sure how to get it without hard-coding.
I want the rotation value to change depending on where my mouse is at a given time. For example, if my mouse is at a 45 degree angle on the 3D globe, I want to know that. I'm trying to constantly re-draw an ellipse until I release the left click on the mouse, so I need my params to constantly update until I'm finished drawing the ellipse.
In Cesium.Cartesian3 there is a static function named "angleBetween". The documentation says it returns "the angle between the Cartesians". What does that mean? What angle? I was hoping it would return a value I could use as the "rotation" in my first question, but it doesn't look like that is what it's trying to do.
Any help on either question is much appreciated!