How to convert Vector to z rotation angle

Question

Please help.

My camera orientation on 3D max is:

90 -30 0

When I export to X3D file it will have this orientation:

0, 0, -1, -0.524

And I can easily convert this to the angle of the camera on the z axis like this:

-1 * -0.524 * 180/Math.PI = 30;

Problem:

But when I rotate the camera on 3D max to:

90 -30 90

on X3D I get this vector:

-0.251, 0.935, -0.251,-1.638

How can I figure out the value of z angle?

Answer 1

Found a way to do it in Stage3D, probably the same on other platforms:

first you create an empty matrix3D:

var m3d:Matrix3D = new Matrix3D();

then you rotate it with the given orientation vector from the X3D file:

m3d.appendRotation(v.w*180/Math.PI,new Vector3D(v.x,v.y,v.z));

decompose the matrix

var angles:Vector3D = m3d.decompose("eulerAngles")[1];

you get xyz angles in radians so turn radians to degrees:

var _z:Number = angles.z*180/Math.PI;