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AUGUST 14, 2003 Swimming with the Fishes
Step 10: Now we are going to do a little expression writing to get our fish tail to swish. With the Null Object selected, press the R key on the keyboard to bring up the Rotation Property for this layer. That is all we are going to do for the moment. We only opened the property so we can Pickwhip to it later.[an error occurred while processing this directive]Step 11: With the first letter layer selected press the R key on the keyboard to bring up the Rotation property for the layer. Hold down the Option key (Alt key on the PC) and click on the Stopwatch Icon for the Y-axis layer to activate the expression window.  Step 12: Use the Pickwhip from the First letter layer and target the Y Rotation of the Null Object layer. Or if you want to do it the long way, type the following expression in the expression window: thisComp.layer(“Null 1).rotationY  Step 13: Repeat Step 12 for the other letter layers in the composition  Because of the position of the Null object and the fact that the Y Rotation of the letters is parented to the Null Object layer, those letters further away from the Null Object appear to rotate more than the letter in front. If you switch to a Top View, you can see the results in better detail.  Incidentally, Brian Maffitt has demonstrated this technique to create a 3D cylinder in After Effects. Because rotation is parented to the Null Object, you can make the cylinder curl from round to flat. But this is a fish, and unless we want to break its little back, we would really rather have it swim along. To do this we’ll add one more expression, this time to the Null Object. Step 14: Option+Click on the Y Rotation Stopwatch for the Null Object. Type the following expression: Math.sin(time*10)*10 This math formula takes the current time and finds the sine of the value (a number between 0 and 1), multiplies that by 10 to get a whole number, and then takes the whole number and multiplies that by 10 to get a value between –10 and 10. Since the expression creates a wave motion, your fish’s tail swishes back and forth. Precompose all of the layers and then animate the position of your completed fish across the screen.
If you want to dissect this exercise, you can download the AE6.0 project file here. When not working deep in the labs of the DMN Central Division testing the latest and greatest software/hardware products Stephen Schleicher can be found at the local university teaching a few courses on video and web production. He can be reached at schleicher@mindspring.com. You can also visit him on the web at www.mindspring.com/~schleicher Related sites: • Animation Artist • AV Video • Broadcast Newsroom • Content Mastering • Corporate Media News • Creative Mac • Digital Animators • Digital Post Production • Digital Producer • Digital Video Editing • DTV Professional • DV Format • Film and Video Magazine • Mac Supplement • Production Supplement • Siggraph News • The WWUG Related forums: [an error occurred while processing this directive] 
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