[gui] how align 3D(Button or StackPanel) Object?

[nedcrow]

I want align 3D object by left order.

But, cleared ultimately goal. https://forum.babylonjs.com/t/parse-convert-tovector3-by-reference-to-canvas-or-viewport/3970/12

And playground :
https://playground.babylonjs.com/#JQJ8UM#6

Thank you!