Weird output debugging the forward of an object with InverseTranformDirection

Question

sorry for my bad english! I will try to explain the situation. Im just playing with this function because i want to understand how it works. The concept is really clear but debugging the forward of the object that i am debugging i get really weird output. For example im using InverTranformDirection(Vector3.Forward) to see what vector i get from the object child of another object. They are both perfectly aligned with their own axies. If i try rotate the parent of the object in order to have the forward pointing at (0,0,1) the child object that i am debugging has the same z axis value like it should have because they are alligned but if i rotate the parent to get the forward rotated on the (1,0,0) space cordinates, i get the cordinates inverted (-1,0,0). I mean why? Parent and child are pointing they own forward in the same exactly direction. Could you help me understand? Thanks!

Answer 1

InverseTranformDirection(Vector3.Forward)

wouldn't care about the parent at all. It is simply converting the world space global Z axis direction (= (0, 0, 1)) into local space of the according object.

I'd say it does exactly what you would expect.

Rotating your object to its own forward vector points towards (1,0,0) (=Vector3.right = world X axis) basically means the world space forward vector (0, 0, 1) (=Vector3.forward) is now pointing left away from your object.

Which is what (-1, 0, 0) would mean in its local space.

Vector3.forward (= -transform.right)
(world Z axis)     (local negative X axis)
^
|
|

rotated Object ----> Vector3.right (= transform.forward)
                     (world X axis)   (local Z axis)