Finding difference between gameObject's x coordinate according to one object's transform

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Okay, forgive the crude illustration, but it's the best way to demonstrate my problem:

alt text

The black boxes are gameObjects, and the red dots are their transform's origin. Likewise the arrows demonstrate their transform's current direction/rotation. I want to find the difference in their x position, according to the bottom left gameObject's transform(red axis). In world coordinates, this would be a number greater than zero, but In my case it should return close to zero, if you get what I'm saying.

Now I thought this would be very simple with transform.right like so:

var diffX = transform.position - other.transform.position;
diffX = Vector3.Scale(diffX ,transform.right);

I also tried:

var tempF = transform.position.x - other.transform.position.x;
var diffX  = Vector3(tempF, 0 ,0);
diffX = transform .TransformDirection(diffX);

Neither one gives the correct result. Any ideas? This one is driving me bonkers.

Answer 1

Best Answer

Answer by duck · May 18, 2010 at 11:10 AM

You need to convert the target object's world position to a relative local position, in relation to the source object. You can do this with InverseTransformPoint.

For instance, attach this to object A (the bottom left object):

var localPosB = transform.InverseTransformPoint(objectB.transform.position);

This means that "localPosB" now contains a vector which represent's object B's position in coordinates relative to object A's orientation and position.

Then, you can get the difference in objectA's local X axis, by simply checking the x component of localPosB, eg:

var diffX = localPosB.x;

Hope this works for you!

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dhendrix · May 18, 2010 at 12:53 PM 0

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Fantastic! This is exactly what I wanted! Thanks!

Finding difference between gameObject's x coordinate according to one object's transform

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