DirectX + bullet what about units?

[noatom]

If in DirectX I am using no units,just plain pixels as by default.
How am I gonna match the sizes of bullet?

I mean if I create a collision shape sphere in bullet with radius 1,how do I know how big should the DirectX sphere be?

[codetiger]

This question applies for any rendering system and not limited to Directx.

However, you can choose to have your own scale for drawing everything on DirectX. This doesn't change anything as changing the scale in drawing doesn't change the way it looks. It all depends on where you place the camera.