Apart from the sheer loveliness of the Director Ang Lee and DOP Claudio Miranda's images, the CGI animals take animation to a new and previously unattainable level. No-one thought it could be done.
So how was it done?
All is revealed in this video. Organised by Arri, who have had an unbelievably good cinematic year with this film and (for example) Skyfall shot with their Alexa cameras, Digital Effects Supervisor Jason Bayever of Rhythm and Hues talks us through - and shows us - how he and his team did it.
You may need to watch this several times. The sequence showing the CGI breakdowns is very fast, and you can easily miss things. For anyone that didn't know how it was done, the revaluation that the entire anatomy of the animals - right down to the detailed musculature - is modelled, will be astonishing.
Pull up a comfortable chair and enjoy...