Creating a particle beam on mulitple layers and in X,Y,Z space

[Darby Edelen]

[Peter Gagnon] “I though about using a null to control the positions with an expression, etc… but I can never fully get this to work… Any ideas?”

I don’t have enough experience with 3D Stroke to give you a solution for that effect, but you should be able to do something like this with Particular. I’d even suggest using 2 Nulls, one for the source and one for the destination. Then you could interpolate the position of the emitter from one to the other between layer markers.

in = thisComp.layer("Muzzle");
out = thisComp.layer("Destination");

try{
i = marker.index(1).time;
o = marker.index(2).time;
}
catch(myErr){
i = inPoint;
o = outPoint;
}

linear(time, i, o, in, out);

A couple of notes: this attempts to use the first two markers on the layer as the start and end times for the shot, if one of these 2 markers doesn’t exist then it uses the layer in point as the start time and the out point as the end time. Also, this returns a three dimensional vector if the Nulls (Muzzle & Destination) are 3D layers, so you’ll need to split the result into X & Y and Z values for Particular:

p = linear(time, i, o, in, out);
p[0,1]

and

p = linear(time, i, o, in, out);
p[2]

Should work pretty well though.

Darby Edelen
Designer
Left Coast Digital
Santa Cruz, CA

[Peter Gagnon]

Wow! That’s cool… I am still trying to wrap my head around it… I guess the destination null is what is confusing me. I am gonna d a test now… thanks.