Expose objects' frustum culled state

Description of the problem

The WebGLRenderer already calculates whether an object is frustum culled, using an internal Frustum.

It’d be nice if this information was exposed so that we don’t have to duplicate the Scene traversal and calculations with our own Frustum outside of the renderer.

A couple ideas:

• Maybe Mesh objects can have an onFrustumCullChange property that is undefined or null by default. If it is set to a function, then when the frustum culling for the object changes the function can be called with true or false.
• Another idea would be to just set a boolean flag on the Mesh objects, but this would make logic relying on it be one frame behind. In most cases it wouldn’t be a problem. The user could make the property into a getter/setter to achieve the same feature as the onFrustumCullChange idea.

Any other ways to do it without requiring a second traversal and calculations?

Three.js version

• Dev

Browser

• All of them

OS

• All of them

[mrdoob]

I guess you can currently do this hack:

object1.onBeforeRender = function () { this.userData.inView = true } );

// render loop
scene.traverse( function ( child ) { child.userData.inView = false } );
renderer.render( scene, camera );

But I agree with @Usnul. I would use cannon.js or something.

[trusktr]

In my current case I’m doing the in-view detection only once when the user stops dragging an object, and not every frame, so performance is not as important in my current case, but I could see this being important if the detection needs to happen every frame, especially if there’s many objects in the scene.