three.js detect off-screen objects?

offscreen.js

var frustum = new THREE.Frustum();
var cameraViewProjectionMatrix = new THREE.Matrix4();

// every time the camera or objects change position (or every frame)

camera.updateMatrixWorld(); // make sure the camera matrix is updated
camera.matrixWorldInverse.getInverse( camera.matrixWorld );
cameraViewProjectionMatrix.multiplyMatrices( camera.projectionMatrix, camera.matrixWorldInverse );
frustum.setFromMatrix( cameraViewProjectionMatrix );

// frustum is now ready to check all the objects you need

console.log( frustum.intersectsObject( object ) );

// http://stackoverflow.com/questions/17624021/determine-if-a-mesh-is-visible-on-the-viewport-according-to-current-camera