Previsualisation is a relatively new feature in filmmaking.
The idea of Pre-Vis is that 3d characters are used in a basic animation of the scene.
This is vital when movement is a key factor in the scene.
Normally this is used in chase or high special effect scenes.

In this case is was an opportunity to seek dramatic camera angles and perspective on the lens, rather than the actors waiting around while the scene is being set up, and possible reshot if it did not flow together well or didnt have enough punch.

Here is a basic comparison between the Pre-vis and the final shoot.