heh - In today's more typical rainy English weather I took your idea and rather ran with it - ended up with
this:
...Anyway was intending to explain the whole 'fan' thing..
Take your fan layer, and move it's anchor point to where you want it to be. Add a null object above it called 'FanControl' and add to that an angle expression control called 'Spread'.
Position the null in roughly the same place as the fan layers anchor point and parent the fan layer to the null. this just makes the fan easier to move about later.
Now Alt-click on the fan layer and add the following expression under rotation:
pos = index-1;
angle = -5;
if (thisComp.layer("FanControl").effect("Spread")("Angle") >pos*angle){
pos*angle;
}else{
thisComp.layer("FanControl").effect("Spread")("Angle")
}
This (in order) does the following;
Sets 'pos' as index - 1. Index is AE's reference to the layer number - we're subtracting 1 because our null is layer number 1.
Sets 'angle' as -5. This is the difference between each layers rotation value. -5 worked for me, but put what ever you like. (It's '-' because that made it rotate in the right direction ;) )
The next part checks the value of the 'FanControl' layers 'Spread Angle'. If it is greater than it's position number * the difference angle, it will set it's rotation to whatever it's pos*angle is. Otherwise it will set it's rotation to whatever the Spread Angle is. Essentially we've set a maximum rotation value for each layer with a 5 degree difference between them. Each layer will follow Spread Angle until it gets larger than their maximum value, at which point they'll stay put.
To get this all to work, duplicate the FanLayer a number of times, and change the spread angle. You might need to rotate the null, to get the fan on screen properly, but it looks pretty good.
Hopefully that all makes sense; it's a good use of expressions (except it could probably be made 'cleaner') - if you're interested in learning more expression stuff I can really recommend
this book which manages to explain it all surprisingly well.
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Only in after effects do children get to pick and whip their parents.
http://hennell-online.co.uk
