[David Conklin]

To get this to work, you need to know what the Y-val of your character would be on the ground as well as when he’s in the air. Additionally, you need to know what rotation vals you want those states to correspond to. Once you have those 4 values, it’s a very simple expression to link the two. For instance you could put this expression on your hair layer’s rotate property.

This expression, in simple terms, basically says as yPosition goes from 0 to 100, rotation goes from 0 to 60.

Hope it helps!

//get the jumping layer
var jump = thisComp.layer("jump_control").transform.position[1];

//get values
var groundY = 0; //the value of your character on the ground
var jumpY = 100; //the value of your character in the air
var groundRotate = 0; //the hair rotation on the ground
var jumpRotate = 60; //the hair rotation in the air

//use linear() to match these values
linear(jump, groundY, jumpY, groundRotate, jumpRotate);