Thanks for your posts, yes have seen the headline radial demo it and it was in fact the inspiration for something to use as an educational display in a museum, next to some WW1 aeroplanes/engines, in fact I confess that I learnt most of what I know from that work by Yu-Sun Chang.
The geometry for the rotary is far more complex since there are two centres of rotation. My thoughts were that by using the one known angle at the centre, taken from the animator, I could use the Sine law and then calculate polar co-ord's. (The length between the centre of rotation is fixed and so is the length of the con-rod). But in practice the geometry does not seem as straightforward as I had expected, with a bit of practice the graphics are relatively simple (mainly a bunch of cylinders) once the geometry is done. The logic seems to work well enough in a spreadsheet calc but maybe I am not interpreting the animator output value correctly, its strange that some bits work fine but others are throwing wrong, but consistent, values.
