// Make Layers React to a Mask// Based on knowledge from The Power of Expression Book// https://aescripts.com/the-power-of-expression///// Requires the new 'Javascript' expressions engine introduced in AE 16.0 (CC2019)// You can set this in File -> Project Settings: https://drop.aescripts.com/NQurXWmG// If you replace all "let" to "var" this expression will should work in previous versions//// v1 initial version// v2 added feathering support// v3 added parenting supportlet maskToUse = thisComp.layer("MASK").mask("Mask 1").maskPath.points();let positionLayer = thisLayer.toComp([transform.anchorPoint[0],transform.anchorPoint[1]]);let inside = function(point, path) {let x = point[0],n        y = point[1];let result = 0;let inside = false;for (let i = 0, j = path.length - 1; i < path.length; j = i++) {let xi = path[i][0],n            yi = path[i][1];let xj = path[j][0],n            yj = path[j][1];let intersect = ((yi > y) != (yj > y)) &&(x <(xj - xi) * (y - yi) / (yj - yi) + xi);if (intersect) inside = !inside;let t1 = length(path[i],point);let t2 = length(path[result],point);if (t1 < t2){n                        result = i;}}return [inside,result];};let lengthToLine =  function(a, b, c) {let line = Math.pow(length(b,c),2);if (line === 0) return Math.pow(length(a,b),2);let d = ((a[0] - b[0]) * (c[0] - b[0]) + (a[1] - b[1]) * (c[1] - b[1])) / line;n        d = Math.max(0, Math.min(1, d));let distance =  Math.pow(length(a, [ b[0] + d * (c[0] - b[0]), b[1] + d * (c[1] - b[1]) ]),2);return Math.sqrt(distance);};let r = inside(positionLayer, maskToUse);let final, distance1, distance2, result2;if (r[0] == true) {n    thisProperty.key(2).value;} else {let closest = r[1];let fallOff = thisComp.layer("MASK").mask("Mask 1").maskFeather[0];n        final = thisProperty.key(1).value;if (fallOff!=0){if (closest==0){n        distance1 = lengthToLine (positionLayer, maskToUse[closest], maskToUse[maskToUse.length-1]);n        distance2 = lengthToLine (positionLayer, maskToUse[closest], maskToUse[closest+1]);} else if ((closest+1)==maskToUse.length){n        distance1 = lengthToLine (positionLayer, maskToUse[closest], maskToUse[closest-1]);n        distance2 = lengthToLine (positionLayer, maskToUse[closest], maskToUse[0]);} else {n        distance1 = lengthToLine (positionLayer, maskToUse[closest], maskToUse[closest-1]);n        distance2 = lengthToLine (positionLayer, maskToUse[closest], maskToUse[closest+1]);};if (distance1 < distance2){n        result2 = distance1;}else{n        result2 = distance2;};nnn        final = linear(result2,0,fallOff,thisProperty.key(2).value,thisProperty.key(1).value);};nn        final;};