Implement highlight on hover using a Color Picking technique

[martinRenou]

For now this is only a visual effect, the state is not synced between clients. We can discuss in an issue whether this could be useful or not.

color_picking.mp4

[trungleduc]

Thanks @martinRenou, It looks great!
For sharing state with other users, I don't think it is useful but is it possible to highlight an object when we select it from the control panel?

[martinRenou]

So actually, maybe instead of an "highlight on hover" behavior, it would make sense to implement a click selection, and when you click on the piece it selects it in the control panel?

That way we can both select from the control panel and select from the 3D view.

[trungleduc]

Freecad has both hover and selection events, but I think the selection is more useful.

That way we can both select from the control panel and select from the 3D view.

That's great!

[martinRenou]

Let's do just like FreeCad! The color-picking being super cheap, I think we can afford it.

[martinRenou]

I implemented both an hover logic and a click logic for selection:

click_hover.mp4

We can bind the control panel UI to the actual 3D selection in a separate PR

[trungleduc]

Thanks!