Matrix decomposition

MatrixDecompose.js

/**
 * Decompose a THREE.Matrix4 into translation, rotation and scale. 
 */
var translation = new THREE.Vector3();
var rotation = new THREE.Quaternion();
var scale = new THREE.Vector3();

// decompose!
matrix.decompose(translation, rotation, scale);
		
var mt = new THREE.Matrix4();
var mr = new THREE.Matrix4();
var ms = new THREE.Matrix4();
		
// and recompose...
mt.setTranslation(translation.x, translation.y, translation.z);
mr.setRotationFromQuaternion(rotation);
ms.setScale(scale.x, scale.y, scale.z);
	
matrix.identity();	
matrix.multiply(mr, ms);
matrix.multiply(mt, matrix);

// check whether the matrix is still sound!

// here the relevant THREE.Matrix4 code:
	decompose: function ( translation, rotation, scale ) {
		// grab the axis vecs
		var x = new THREE.Vector3(this.n11, this.n21, this.n31);
		var y = new THREE.Vector3(this.n12, this.n22, this.n32);
		var z = new THREE.Vector3(this.n13, this.n23, this.n33);
		
		translation = (translation instanceof THREE.Vector3) ? translation : new THREE.Vector3();
		rotation = (rotation instanceof THREE.Quaternion) ? rotation : new THREE.Quaternion();
		scale = (scale instanceof THREE.Vector3) ? scale : new THREE.Vector3();
		
		scale.x = x.length();
		scale.y = y.length();
		scale.z = z.length();
		
		translation.x = this.n14;
		translation.y = this.n24;
		translation.z = this.n34;
		
		// scale the rotation part
		var matrix = this.clone();
		
		matrix.n11 /= scale.x;
		matrix.n21 /= scale.x;
		matrix.n31 /= scale.x;
		
		matrix.n12 /= scale.y;
		matrix.n22 /= scale.y;
		matrix.n32 /= scale.y;
		
		matrix.n13 /= scale.z;
		matrix.n23 /= scale.z;
		matrix.n33 /= scale.z;
		
		rotation.setFromRotationMatrix(matrix);

                return [translation, rotation, scale];
	},