Problems with Vector3.Angle... Anyone have any ideas?

Target Platforms Mobile
1

Hey, all,

I’m working on a pretty maths heavy game, which involves loads of calculations between vectors, but I’m having real issues with Vector3.Angle.

Every other frame, I get the same result as I got the previous frame, but as a negative version of the prior, like so:

Frame 1:
Angle = 180.5
Frame 2:
Angle = -0.5
Frame 3:
Angle = 180.5
Frame 4:
Angle = -0.5

At first I thought it was my code (obviously), but then I tried the following:

Angle = Vector3.Angle ( Vector3.up, Vector3.left );

Which gave the following results:

Frame 1:
Angle = 90
Frame 2:
Angle = 0;
Frame 3:
Angle = 90;
Frame 4:
Angle = 0;

This isn’t really much use to me, as I really need to know what the actual angle is or my calculations are all out.

Is this a bug? Or something I’m missing?

Anyone have any ideas how to get around it?

Cheers,

SB

2

Looks like each frame you’re rotating Angle exactly 90 degrees :slight_smile:

It suggests to me (though I don’t see how) that Vector3.up etc is relative to Angle present orientation, even though I didn’t think its meant to do that?

Nope, I’m no help at all, I’m confused :slight_smile:

3

Can you post the whole script? Vector3.Angle isn’t supposed to be dependent on any kind of game state, so it would be very strange for it to behave like this.

4

You don’t actually need the whole script! Doing the following:

function Update()
{
     Debug.Log ("Angle = "+Vector3.Angle (Vector3.forward, Vector3.left) );
}

demonstrates exactly what I’m talking about. If you run it, you get:

Angle = 0;
Angle = 90;
Angle = 0;
Angle = 90;
etc…

Obviously this isn’t the code in my game, but I’d taken my script apart to a point where I decided to run this as a test, and got the above results. Really weird, and very difficult to work around - it’s messing up my compass! :frowning:

5

Have you tried below just to see if its the syntax?

function Update()
{
     Debug.Log ("Angle = "+Vector3.Angle (Vector3(0,0,1), Vector3(-1,0,0) );
}

Also, I dont see a Vector3.left in the script documentation. I am assuming its just not mentioned but does exist.

6

Yes, strictly speaking, Vector3.left is a relic that isn’t supposed to be used (which is why it is undocumented). I’m running this by the dev team to see if using Vector3.left could be causing the problem.

7 
	void Start () 
    {
        Debug.Log(Vector3.Angle(new Vector3(0, 0, 0), new Vector3(0, 10, 10)));
        Debug.Log(Vector3.Angle(new Vector3(0, 0, 0), new Vector3(10, 0, 10)));
        Debug.Log(Vector3.Angle(new Vector3(0, 0, 0), new Vector3(10, 10, 0)));
        Debug.Log("next");
		Debug.Log(Vector3.Angle(new Vector3(0, 0, 0), new Vector3(10, 10, 0)));
        Debug.Log(Vector3.Angle(new Vector3(0, 0, 0), new Vector3(10, 0, 0)));
        Debug.Log(Vector3.Angle(new Vector3(0, 0, 0), new Vector3(10, -10, 0)));
        Debug.Log("next");
		Debug.Log(Vector3.Angle(new Vector3(1, 0, 0), new Vector3(11, 10, 0)));
		Debug.Log("next");
        Debug.Log(Vector3.Angle(new Vector3(5, 6, 7), new Vector3(10, 10, 0)));
        Debug.Log(Vector3.Angle(new Vector3(5, 6, 7), new Vector3(10, 0, 0)));
        Debug.Log(Vector3.Angle(new Vector3(5, 6, 7), new Vector3(10, -10, 0)));


	}

and its output
90
90
90
next
90
90
90
next
42.27369 :wink:
next
42.13
61
93

I am guessing this is because angle is a canonical Euler angle and its entering Gimbal lock so you get 90 when you would expect 45.

Angle could use better documentation. Note I did not test this in Unity iPhone

8

it is quite simpe if you know the conditions clearly.
This image illustrates it (i am using x/z axis):

the code would be like:

var A:Vector3 = Vector3( 0.0, 0.0, 1.0 ) // x,y,z
var B:Vector3 = Vector3( 1.0, 0.0, 1.0 ) // x,y,z
var angle:float = Vector3.Angle( A,B );
    // angle == 45

Debug.DrawLine ( Vector3.zero, A, color.yellow ); 
Debug.DrawLine ( Vector3.zero, B, color.yellow );

so what we do here is set the Vector A along the z-axis and the Vector B along the x/z plane.

The important thing to understand is that (if i’m not mixed up) Vector3.Angle always calculates the angle from the Vector3.zero to the actual Points.