Emit event when visible changed

[DennisSmolek]

Description

We have events that fire when an object has children added/removed, or it moves around itself, but it would be great if we fired a event when the visibility of an object changes.

Right now we have to query the entire scene every frame which is less performant.

Solution

Add a visibilty event to objects

Alternatives

Traverse the scene every frame and check objects current status against a registry of it's last status

Additional context

No response

[Mugen87]

Traverse the scene every frame and check objects current status against a registry of it's last status

You can use Proxy for this as well. This works for detecting changes in any properties:

https://jsfiddle.net/czw7rqLu/

[DennisSmolek]

Traverse the scene every frame and check objects current status against a registry of it's last status

You can use Proxy for this as well. This works for detecting changes in any properties:

https://jsfiddle.net/czw7rqLu/

This requires proxying every single object to get the functionality and proxies have issues with some of the renderers/materials so I've had to unproxy them.

Both cases would be easier to monkey-patch this onto.

When doing a visibility check in-frustum doesn't mean visible, neither does occlusion checks.
When doing those I am doing a visibility check as well.

However I've built the traversal checks before or had to manage my own records of scene items solely to check the visibility state.

I guess I don't understand why it's an issue. This is built on an event emitter and there's events for children and parents, why the hesitation on the visibility prop?

Like I said we have this in r3f and thought it would be useful.

If you think it a bad idea then it's ok!

[Mugen87]

why the hesitation on the visibility prop?

Because developers could easily request to expand the event dispatching to any other 3D object and material property, creating a lot of unnecessary events that most users don't need. Even the visibility event will be useless for many apps and there is no way to disable the dispatching unless users monkey patch the library to opt this out.

Besides, I've used Proxy in other contexts and had no issues with it. I would like to know first what kind of problems you have encounter and investigate if there is a way to solve them. JavaScript provides us a feature for exact this use case and the beauty of it is it can be opted-in by applications.