• Adobe After Effects Expressions

  nascar text follow track point with scaling arrow or pointer

  Posted by Chris Abolt on December 4, 2007 at 7:35 pm

  Hi all,
  I am trying to create text that will follow a car via tracking point on car ftg. The text will pop out of certain features areas of the car and have attached arrows that reference points on the car. I need the arrow points to stay attached to the car while the txt looks at the camera and moves with the car. This is best seen on the nascar real time update tags attached to cars as they move around the track. I have created the text and tracked the car. I have parented the text to a tracked null and positioned them in 3d space around the 2d car. I just need an expression to attach the arrows to tracked places on the car and have them automatically scale (stretch) and move with the the car as the txt stays stationary????? Help would be greatly appreciated.

  Chris Abolt replied 18 years, 5 months ago 3 Members · 4 Replies
• 4 Replies

• 

  Darby Edelen

  December 5, 2007 at 12:06 am

  I think this would best be handled by a combination of the Beam effect with an expression on the start point to follow the arrow’s anchor point:
  
l =thisComp.layer("Arrow");
l.toComp(l.anchorPoint);

  And an expression on the end point to follow the text’s anchor point:
  
t = thisComp.layer("My Text");
t.toComp(t.anchorPoint);

  And an expression applied to your arrow layer’s rotation. Something like this:
  
t = thisComp.layer("My Text");
l = thisComp.layer("Arrow");
offset = -90;

  v = l.toComp(l.anchorPoint) - t.toComp(t.anchorPoint);

  radiansToDegrees(Math.atan2(v[1], v[0])) - offset;


  Darby Edelen
  Designer
  Left Coast Digital
  Santa Cruz, CA
• 

  Darby Edelen

  December 5, 2007 at 12:07 am

  Just another note, the Beam effect in this scenario needs to be applied to a solid layer the same dimensions as the composition.

  Darby Edelen
  Designer
  Left Coast Digital
  Santa Cruz, CA
• 

  John Lacroix

  December 7, 2007 at 5:00 am

  I’m curious to see your final results. Coincidentally, I’m the creative director for the company (sportvision.com) that does the NASCAR pointers that you see on TV and for the network clients, we mock up a lot of the effects before we write the software to take them to air.
• 

  Chris Abolt

  December 7, 2007 at 2:17 pm

  Hi all,
  OK here was my solution and thanks to those suggestions that were submitted. (1) I Tracked the position and scale of the car as it moved. (2) In the same comp I created a text layer and a solid layer. (3) I applied the corner pin plug-in to the solid and adjusted it to look like a pointer under my text. I also adjusted the anchor point of the pointer so the anchor was at the top of my pointer (4) I parented the text to the pointer.
  (5) In the same comp I created a null. (6) I used the pickwhip to create 2 expressions that attached the 2 lower corner pin points (the point of the pointer) to the position of the null.
  (7) I transfered the tracked information to the pointer layer so it will follow the car. (The anchor point may have to be adjusted to get the pointer and parented text exactly where you need it).
  (8) Now the null can be hand animated to position the point of the pointer or tracking data can be applied to the pointer for effortless positioning.

  Any who are interested I can email the comp or a small movie.
  This was fun to figure out.

  Chris Abolt
  Motion designer
  Abolt Media

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