Blackmagic Forum

Hi

I wanted to produce a graphic, that has two circles and a dot offset from the centre of the second circle. The second circle rotates around the circumference of the first, and the resulting shape is an epitrochoid.

I’m perfectly happy using shape nodes to produce the animation, but I wanted to find a way to have the dot draw a nice clean line. The only way I could think of to solve this was to use a trail node to record the path the dot had taken. It works, but I would much rather have a nice clean line, and not a trail of dots.

Is there any way to track the X/Y co-ordinates of a moving object (in this case a shape node, being animated by two transform nodes), and pass that information onto another node that can draw it’s path?

I mean, *I could* just draw a poly and animate that but I wished to find a more elegant solution.

You could try tracking the dot, then connecting a Paint node Polyline stroke to the path of the tracker. In the attached image, I animated an ellipse to move across screen while rotating around an offset point. I then tracked it and then used a Paint node connected to the tracked path.

One way of doing this is by making the animation way way slower than you'd want it to be and then using the trails tool to draw the line, then put a timespeed tool after the trails tool and speed the result back up to what you want it to be. This way you'll probably be able to avoid spaced dots.