[Greg McKaskle]

We know and expect the soccer to produce a circular shape, so we see a circle. The balls cast shadows and the edge is not well controlled, so the algorithm for detecting a strong edge between light and dark around the ball will often fail at some point. For that reason, the circle detection isn't a great way to spot the balls.

I've posted info on ni.com/first discussing a pretty effective that looks for circular holes in the carpet. The carpet is pretty consistent and can be masked using color or even better, luminance. You can invert the mask, remove small particles, remove edge particles, and you are ready to get a particle report. Some of the fields you can ask for in the report compare perimeter distance to area, and if you think about the math, that is a pretty good filter for circular shapes. You may want to put in a few other filters and fiddle with the range, but you can build a particle based ball tracker pretty easily.

Also keep in mind that the camera needs to be mounted so that it can see the carpet in front of it.

Greg McKaskle