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Three.js - Rotating a sphere around a certain axis

rated 0 times [ 11] [ 7] / answers: 1 / hits: 35685 / 11 Years ago, wed, may 1, 2013, 12:00:00

I have a problem. In Three.js, I want to rotate a sphere (Earth) around axis tilted by 23.5 degs. I found sphere.rotation.x, sphere.rotation.y and sphere.rotation.z, but when I combine them in the correct ratio, the sphere's rotation is quite weird - it has no permanent rotation axis. I think I need a function like sphere.rotation.vector(1,0,-1). Does anyone know how this function is called and how the correct syntax is?

Many thanks for answers!

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makaylahk

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answered 11 Years ago alorafrancisl · Accepted Answer

You need to use quaternions for this. This video explains what quaternions are and how they are used in 3D graphics.

You can construct a quaternion like this:

quaternion = new THREE.Quaternion().setFromAxisAngle( axisOfRotation, angleOfRotation );

Then you apply it to your object by:

object.rotation.set( new THREE.Euler().setFromQuaternion( quaternion ) );

You can also achieve this by using object hierarchies. For example, you can make an Object3D() instance and tilt it by 23.5 degs, then create a sphere (Earth) and add it to the tilted object. The sphere will then rotate around the tilted Y axis. Quaternions however, are the best tool for solving this.