How to handle GUI interactions / pointer events in Offscreen Canvas?

I’m currently trying to figure out how to handle GUI elements the user interacts with via pointer events like buttons when used with offscreen canvas / web workers, but had no luck so far.

I know that that for mesh picking I can use scene.pick(). That does however not work for GUI elements and I dont see any picking/hit test available on AdvancedDynamicTexture. Do I need to create my own control picking logic or is there some feature already in the library? What is the usual method used in such cases?

Hello and welcome to the Babylon community!
There’s doPicking, but it’s a private method currently: Babylon.js/advancedDynamicTexture.ts at master · BabylonJS/Babylon.js (github.com)
@RaananW do you think we could expose it somehow? :thinking:

I will not be very happy exposing this function (even though there is “nothing to hide”, but I can suggest this - we have a way to simulate pointer events simulatePointerUp/Down/Move are used extensively throughout the framework and are probably the solution you are looking for. They are a part of the scene.

2 Likes

I already tried it with scene.simulatePointer*(), but it didn’t work:

The doc string for simulatePointerUp also explicitly states that it’s for simulating pointer events on a mesh. So I guess that’s the desired behavior, or am I missing something here?

When simulating pointer events, you need to do the picking yourself and pass the pick info.
But this won’t work with fullscreen UI, which is what I assume you are trying to achieve?

In that case we will need to expose some sort of a picking method for the ADT. It’s neither the private _doPicking ot the private _translateToPicking, so we’ll have to think about it.

1 Like

Yes, I’m using a fullscreen UI. A simplified version of what I’m trying to achieve is here:

It’s a draggable pop up box, showing information about the picked mesh.

I have very little understanding of the inner mechanics of Babylon, so this might (probably) be a stupid question, but would it be possible to create a virtual DeviceInput, i.e. a mock/proxy of webDeviceInputSystem delegating the events on the canvas via the web worker’s message bus?

[GUI] add picking for fullscreen ADTs by RaananW · Pull Request #13039 · BabylonJS/Babylon.js (github.com)

4 Likes