Create sphere on keyframes with expression

Question

Hi,I've just begun to learn after effects and could use a little help.I have a small solid wich is moving around on the comp. This is done using expressions.What I would like to do is first to replace it with a 3d sphere. And secondly, instead of moving it, create a new sphere on each keyframe.First I imagined using trapcode particular, setting the particles count to 1. But that is per second, not per keyframe.Any ideas are appreciated./Lars

Dan Ebberts · Accepted Answer

Oh, thank you. The keyframes only hold a single value so I already have an expression for the position. So the keyframes are in a separate layer.

x=time*20;

note=thisComp.layer("midi").effect("ch_0_pitch")("Slider"); //this is the keyframes

y=linear(note, 60, 74, 0, -100);

centre=[50, 180, 0];

add(centre,[x,y]);

I guess you'll need to combine the two expressions. I don't have time to test it, but this should be close:

note=thisComp.layer("midi").effect("ch_0_pitch")("Slider"); //this is the keyframes

t = time;

if ((note.numKeys >= index) && (time > note.key(index).time))

t = note.key(index).value;

x=t*20;

y=linear(note, 60, 74, 0, -100);

centre=[50, 180, 0];

add(centre,[x,y]);

Dan

Lars Renklint · Answer

My understanding right now is that there probably isn't a "create" method for creating shapes or objects in expressions. Please correct me if I'm wrong.

Instead I should create my shape and then use expressions for duplicating that layer while repositioning it. Does this sound like the correct method?

It would make sense that a keyframe couldn't hold an object. On the other hand it seems you could easily end up with a trillion layers in a comp..

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