Plotter - 3 servos

Hey eziosoft,
i really like your projects and your quick style to do prototypes!

Your servo-arm-plotter is very interesting for me, because I started a similar project. Im not so good in all this programming stuff, but i try my best.

I have a important question and hope you can find time and a way to help me.

Im trying to create some simple graphic in processing (XY coordinates) and want to send them to an arduino which controls a simple 3-servo-arm, like yours.

I just don't see a way, how to convert the XY data to the needed ServoAngle data.

How did you do it???