Hi Pilou,

re:
> That works fine but maybe that is not the good strategy ?
> It's curious that dimension can't works directly in the normal 3D world for any face! :)

It's kind of dangerous for dimensions to be too easily placed in 3D because it can cause ambiguity.

Like for example when you see a drawing like this:


It's important that it should be a measurement of this length:


And not this one which appears the same in the 2D drawing:



So for the purposes of making 2D drawings it's good for dimensions to be placed with some care and it's not great to try to make it really easy to stick anywhere in 3D space even though that would be fun for playing around with them.

- Michael