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Tracking of a ball on a projection

hi ppl, i have a question regarding a current project: i am trowing a ball on a projection and want to track the position of the ball. anyone has ideas how to do this tracking, since there is the projection over the ball so i cannot use color tracking! (color changes all the time)

please help! any ideas?

thanks,
zecko

infrared usually comes to mind in these applications. cheap security cameras usually have very good IR reception. projectors usually give very little IR light.

if you can save some colors, the same technique also works with visible colors. a student of mine once had an installation where she tracked only the red component of a light spot on a projection which was done in various shades of blue.

If you’re front projecting,
how about tracking the shadow of the ball from the rear of the projection?

  1. from the direction you throw the ball, throw some additional infrared (cheap health lamps with a blue filter worked for a student of mine)
  2. from behind the projection, record the scene with a regular camera equipped with another IR filter
  3. track everything black.

thanks oschatz and max – i will try out your suggestions.
looks like i have to realise the tracking from the front, since the material where it gets projected on is not letting any light through…
hope IR and IR-lights will work out