2D LookAt expression doesn’t wanna work

[Lukas Thorsson]

Use this simple Script:

pointA = thisLayer;
pointB = thisComp.layer("Null 2");

a = pointA.position[0] - pointB.position[0];
b = pointA.position[1] - pointB.position[1];
switcher = 0;

if (b < 0) {switcher = -180};
if (b == 0) {degree = 90} else {degree = -radiansToDegrees(Math.atan(a/b))}

degree + value + switcher

The difference between Point a and b can be described as a triangle. The difference on X Axis is line segment a, Y Axis is line segment b, line segemnt c would be the distance, but we only need a and b.

Computing the Angle beween is arctan(a/b). As in https://en.wikipedia.org/wiki/Triangle#Computing_the_sides_and_angles described.

If the difference on y Axis is negative the Triangle “flips”, so we need to rotate the value by 180 degrees. If its zero, we get an divide by zero error, so we’re catching this case also.

By Adding the “value” Argument at the End you can easily rotate your layer to the right direction.

[Konstantin Kartashov]

Hi, Lukas,
it`s a great stuff, thank you. But is it possible to convert these all to screen coordinates? just to make the look at rotation independent from parent object`s rotation.

[Lukas Thorsson]

Hi Konstantin,

try replacing the first 2 lines with

pointALayer = thisLayer;
pointA = pointALayer.toComp(pointALayer.anchorPoint);

pointBLayer = thisComp.layer("Null 3");
pointB = pointBLayer.toComp(pointBLayer.anchorPoint);


Bye

Lukas

[Konstantin Kartashov]

sorry Lukas, but it doesn`t work. It returns the error message “Class `array` has no property or method named `position`”. Could you please suggest any other solutions?

[Lukas Thorsson]

Ooops… I was a bit in a hurry when i made the post…

pointALayer = thisLayer;
pointA = pointALayer.toComp(pointALayer.anchorPoint);

pointBLayer = thisComp.layer("Null 3");
pointB = pointBLayer.toComp(pointBLayer.anchorPoint);

a = pointA[0] - pointB[0];
b = pointA[1] - pointB[1];
switcher = 0;
if (b < 0) {switcher = -180};
if (b == 0) {degree = 90} else {degree = -radiansToDegrees(Math.atan(a/b))}

degree + value + switcher

Same script but without .position @ line 6 and 7. In the first script Variable pointA was a Layer, so pointA.position referred to the layers position. Now we calculate the position using the toComp() Function and save the position to the Variable pointA.

[Konstantin Kartashov]

Thank you very very much. Now it`s exactly what i wanted to get.