Local Vector

Question

I am trying to achieve a negative value for my down vector. This is the code that I have come up with but it is not working. I only want the y values to be negative when going down, all other values should remain positive. I would like to simulate my aircraft gaining speed as it descends, and slowing as it ascends.

 var horizontalVelocity : Vector3 = chopper.velocity;
 var verticalVelocity : Vector3 = chopper.velocity;
 horizontalVelocity = Vector3(chopper.velocity.x, 0, chopper.velocity.z);
 verticalVelocity =   transform.InverseTransformDirection (Vector3(0,chopper.velocity.y,0));
 var totalVelocity = horizontalVelocity - verticalVelocity;
 GUI.Label( Rect(120, 182, 256, 256 ), (totalVelocity.magnitude * 3.6f) + "Km");

Answer 1

Given your follow-up comment, I'm guessing that chopper.velocity is in world coordinates. In your code, totalVelocity is the same as chopper.velocity. That is, when you separate out the components as you've done in horizontalVelocity and verticalVelocity, then add them back together, you just reconstruct chopper.velocity. I'm not sure what you want. Velocity is a vector. Even only horizontally it will not always be positive if it is in world coordinates. If your plane is largely flying forward with maybe a bit of left and right velocity in the turns, then may the local velocity might always be positive. But this is a lot of ifs and assumes some unrealistic physics. What you may want is the speed of the plane and then the rate of asset or decent. Assuming chopper.velocity is in world coordinates, you can calculate it this way:

 var groundSpeed = Vector3(chopper.velocity.x, 0, chopper.velocity.z).magnitude;
 var climbRate = chopper.velocity.y;

These will both be floats. 'groundSpeed' will always be positive. 'climbRate' will be negative if the plane is descending, and positive if it is ascending. You could combine them into a string like:

 var output = "Speed: " + groundSpeed  + "  Climb: " + climbSpeed;

If chopper.velocity is in local coordinates, you will need to do a transform.TransformDirection() first, and then calculate groundSpeed and climbRate off the converted vector. You must convert local to world so that the 'y' component will represent up and down in world space, not along the 'y' axis of the object.

Local Vector

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