 Weta was already working on animating the creatures while the film was being shot, and Weta crew members were on-set for all the scenes that involved special effects during the filming.Weta visual effects supervisor Matt Aitken explained that process involved in interpreting the creatures was "split into two steps".First, natural-looking creatures were created based on pencil sketches by Csupó and Malanitchev, and this was done mostly through Photoshop collages done by visual effects art director Michael Pangrazio.