Here are the two functions I use. They are based on matrix rotations. and can rotate around arbitrary axes. To rotate using the world's axes you would want to use the second function rotateAroundWorldAxis().
// Rotate an object around an arbitrary axis in object space
var rotObjectMatrix;
function rotateAroundObjectAxis(object, axis, radians) {
rotObjectMatrix = new THREE.Matrix4();
rotObjectMatrix.makeRotationAxis(axis.normalize(), radians);
// old code for Three.JS pre r54:
// object.matrix.multiplySelf(rotObjectMatrix); // post-multiply
// new code for Three.JS r55+:
object.matrix.multiply(rotObjectMatrix);
// old code for Three.js pre r49:
// object.rotation.getRotationFromMatrix(object.matrix, object.scale);
// old code for Three.js r50-r58:
// object.rotation.setEulerFromRotationMatrix(object.matrix);
// new code for Three.js r59+:
object.rotation.setFromRotationMatrix(object.matrix);
}
var rotWorldMatrix;
// Rotate an object around an arbitrary axis in world space
function rotateAroundWorldAxis(object, axis, radians) {
rotWorldMatrix = new THREE.Matrix4();
rotWorldMatrix.makeRotationAxis(axis.normalize(), radians);
// old code for Three.JS pre r54:
// rotWorldMatrix.multiply(object.matrix);
// new code for Three.JS r55+:
rotWorldMatrix.multiply(object.matrix); // pre-multiply
object.matrix = rotWorldMatrix;
// old code for Three.js pre r49:
// object.rotation.getRotationFromMatrix(object.matrix, object.scale);
// old code for Three.js pre r59:
// object.rotation.setEulerFromRotationMatrix(object.matrix);
// code for r59+:
object.rotation.setFromRotationMatrix(object.matrix);
}
So you should call these functions within your anim function (requestAnimFrame callback), resulting in a rotation of 90 degrees on the x-axis:
var xAxis = new THREE.Vector3(1,0,0);
rotateAroundWorldAxis(mesh, xAxis, Math.PI / 180);