N1 = thisComp.layer("Null 1"); N2 = thisComp.layer("Null 2"); N3 = thisComp.layer("Null 3"); N4 = thisComp.layer("Null 4"); p0 = N1.position; p1 = N2.toWorld(N2.anchorPoint); p2 = N3.toWorld(N3.anchorPoint); p3 = N4.position; c = 3*(p1 - p0); b = 3*(p2 - p1) - c; a = p3 - p0 - c - b; t = index/(thisComp.numLayers - 3); ((a*t +b )*t + c)*t + p0