In this tutorial I use Video Copilot Orb, CC Particle World, Turbulent Displace, Vector Blur and CC Radial Blur to create a 3D comet.
I also take a look at creating a 2D version you would see in the sky.
Expression
Position X:
x=thisComp.layer("Null 1").transform.position[0]-thisComp.width/2;
x/thisComp.width;
x=thisComp.layer("Null 1").transform.position[0]-thisComp.width/2;
x/thisComp.width;
Position Y:
y=thisComp.layer("Null 1").transform.position[1]-thisComp.height/2;
y/thisComp.width;
y=thisComp.layer("Null 1").transform.position[1]-thisComp.height/2;
y/thisComp.width;
Position Z:
z=thisComp.layer("Null 1").transform.position[2];
z/thisComp.width;
z=thisComp.layer("Null 1").transform.position[2];
z/thisComp.width;
And another for how to link a 2D effect to a 3D position:
thisComp.layer("Light 1").toComp([0,0,0]);
thisComp.layer("Light 1").toComp([0,0,0]);
