Hi Pilou,

re:
> Can we make dimension in the 3D view ?
>
> What is the strategy ?

Well dimensions are focused on making a measurement in a 2D projected view. They are planar objects and when you create them they are projected onto the view's construction plane. You can make them in the 3D view, they are just projected down to the the 3D view's construction plane.

If you want that plane to be somewhere else you can use View > CPlane to set the construction plane to one of your box's faces before you create the dimension.

- Michael