• | **HowTo: Expression Angle Control dictates the Position of a Null**
on Oct 11, 2013 at 3:21:43 am |

As the Subject Title says BUT with an additional requirement - the Null can only move along the perimeter/edge of the Comp.

Cheers

RoRK

Intensive mocha & AE Training in Singapore and Other Dangerous Locations

Imagineer Systems (mocha) Certified Instructor

& Adobe After Effects CS6 ACE/ACI

• | **Re: HowTo: Expression Angle Control dictates the Position of a Null** on Oct 12, 2013 at 11:11:50 pm |

This is probably too late to help, but I finally found enough time to work this one out.

a = effect("Angle Control")("Angle")%360;

if (a < 0) a += 360;

ar = degreesToRadians(a);

w = thisComp.width;

h = thisComp.height;

g = Math.atan2(h,w);

if ((ar > Math.PI*2 - g) || (ar <= g)){

x = w;

y = (h + w*Math.tan(ar))/2

}else if ((ar > g) && (ar <= Math.PI - g)){

x = (w - h*Math.tan(ar - Math.PI/2))/2;

y = h;

}else if ((ar > Math.PI - g) && (ar <= Math.PI + g)){

x = 0;

y = (h - w*Math.tan(ar - Math.PI))/2;

}else{

x = (w + h*Math.tan(ar - 3*Math.PI/2))/2;

y = 0;

}

[x,y]

Dan

• | **Re: HowTo: Expression Angle Control dictates the Position of a Null** on Oct 14, 2013 at 2:56:42 am |

Thanks Dan! This worked wonderfully!

Cheers

RoRK

Intensive mocha & AE Training in Singapore and Other Dangerous Locations

Imagineer Systems (mocha) Certified Instructor

& Adobe After Effects CS6 ACE/ACI

• | **Re: HowTo: Expression Angle Control dictates the Position of a Null** on Nov 25, 2013 at 10:06:21 am |

Hi Dan,

Just found this thread. This is something i wanted to do long time ago. havent found the trick. :P

I have situation here:

I found this code: that calculate degrees from position.velocity. I use linear to animate position. how can i merge this code to make animated current position to angle control? something like direction.

Thanks

Mad

`v = position - position.valueAtTime(time-thisComp.frameDuration);`

radiansToDegrees(Math.atan2(v[1],v[0]))