I need to manually draw some links between points on a circle and points clustered in the centre of said circle. I have the x,y pairs for the source and target points, but I don't want a simple straight line between them; I want a curved line (similar to the links that are found in tree diagrams). I could use linkHorizontal or linkVertical but their tangents are constant; I want to use linkRadial and have the tangent be the radial line at that particular arc point (the degree of which I also have).
I don't understand the linkRadial API though; it wants an angle and a radius, not an x or y point. How do I convert my two x,y pairs (and the radial line angle) into the angle and radius this is expecting?