View Full Version : Challenge: tracking an object w/arrow

04 April 2005, 06:14 PM
I have set up some tracking in my animation successfully, but I want to point at the tracked point with an arrow so that the tip follows the tracked point but the other end of the arrow does not move. How would I go about doing this using the tracking information? The tracking is being used to label parts of a medical animation.


04 April 2005, 08:37 AM
As far as I know there is no out-of-the-box arrow effect.

You can use the effect->render->beam to make a line between 2 points. You can link the ending point to the tracker with an expression.

With a second beam effect you can sort of make an arrowhead. Link the endingpoint to the first beam endingpoint. Link the beginpoint to the first beam effect with this:
(effect("Beam")("Starting Point")+(5 * effect("Beam")("Ending Point")) )/6

Where "Beam" is the name of the first beam effect.
Make the starting thickness higher and the ending thickness lower.


04 April 2005, 03:34 PM
Thanks man! I forgot I posted the question here. I had got as far as using beam to point at a moving target, but had not considered the arrow tip.

04 April 2005, 07:28 PM
Something like this?

04 April 2005, 08:30 PM
I guess, but the arrow is not pointing at something its pointing in the direction it moves. And the yellow arrows are pointed in the same direction as the red one. Like you suggested I am using beam.

04 April 2005, 11:15 PM
Here's my stab at it:

I made both 3D layers and used look_at(this_comp("layer name").position, position) on the Orientation of the arrow. (Layer Name being the tracked object.) You have to move the arrow's anchor point to the end, and tweak the X/Y/Z rotation a bit.

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04 April 2005, 11:15 PM
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