A Brief History of Birds in Film
CG avian creatures as characters have a long history in film and covering all of them would be difficult. I would like to touch on some of the more notable digital avian creatures and discuss relevant work in regard to the rig, feather motion, and challenges faced in each case. Also, while many films have had birds in them, not all of them are relevant. The following brief history discusses avian creatures that fit the scope of this thesis- those that are realistic and not heavily stylized.
The Chronicles of Narnia: The Lion, the Witch and the Wardrobe (2005)
In The Chronicles of Narnia: The Lion, the Witch and the Wardrobe by Walt Disney Pictures with visual effects by Rhythm & Hues there are gryphons: half-lion half-eagle creatures. The gryphons have a small role overall but they are featured in shots, both flying and with wings folded, close up and full frame. This required that the gryphons be highly detailed and as anatomically accurate as a mythical creature can be. A big challenge to this was the look and actions of the feathers [Hiebert et al. 2004].
The feathers on the gryphons (coverts, and body feathers) were generated procedurally using Rhythm & Hues’ in house fur software, except for two rows of flight feathers [Hiebert et al. 2004]. The implementation of feathers this way looked realistic for the gryphon when flying. However, the gryphon’s performance required that he fold his wings. Rhythm & Hues’ default set of tools worked well in general, with few interpenetrations perceptible; the problem came with the flight feathers.
In Rhythm & Hues’ avian rig designs previous to the one used in Narnia, a spline along the trailing edge of the wing that the feathers pointed at was used to control the wing; this allowed the animator to have a lot of control with a minimum amount of control objects and worked well for flight motion. However, for wing folding, it caused the feathers to stack up incorrectly relative to the look and behavior of feathers on real birds. To solve this, the flight feathers were broken up into two separate groups of primary and secondary feathers with a separate spline to control each. It allowed the primaries and secondaries to stack up believably and an additional layer of control was added to allow the animator to control each feather individually and to clean up any feathers that were out of place or interpenetrating [Hiebert et al. 2004]. It works well for wing folding on the two main groups and something similar could be applied further to the separate feather groups in the wing for a more photo-real bird wing.
Harry Potter and the Prisoner of Azkaban (2004): Buckbeak
In the third Harry Potter movie, Harry Potter and the Prisoner of Azkaban by Warner Brothers Pictures with visual effects by Moving Picture Company (MPC), MPC developed highly detailed wings for the hippogriff, a mythical creature that is half horse half eagle, Buckbeak. He was in the film for about 10 minutes, and had several up close, full frame hero shots and, like the gryphons in Narnia, the hippogriff had performances with wings opened and folded. While published information on a bit vague on the production techniques used to make the wing, possibly due to the proprietary nature of the work, Buckbeak is a good example of a wing looking nearly photo-real when opened, but looking unrealistic when closed. When closed it loses believability because of the way the feathers are overlapping; the different types of feathers make angles to one another not found in a real birds wing or overlap incorrectly, causing the wings to look flat.
Every feather on Buckbeak was created was modeled after a real feather in which it had geometry representing the central rib called the ‘rachis’ and filament like barbs and some feathers were even more detailed, using geometry to represent the little Velcro-like hooks holding the barbs together called ‘barbules’. The feather models used depended on camera distance- the more detailed feather models were used for closeups and the less detailed ones were used for distance. A total of 16,500 feathers applied to the hippogriff’s skin [Fordham 2004]. The feathers were driven by MPCs proprietary muscle system enabling skin jiggle. This allowed the feathers to move with the underlying musculature and skin for a more realistic look. The motion of the wings caused problems with the interaction of muscles and feathers. They needed a way for the feathers to stack up correctly when folding and to prevent intersection. The resulting rig prevented penetrations of the flight feathers when folding, using a program that resolved intersections and compressed feathers against one another in the closed wing.
Lord of the Rings trilogy (2001-2003): Gwaihir
For the movie Lord of The Rings: Fellowship of the Ring by New Line Cinema with visual effects by Weta Digital, Ltd. a large eagle named Gwaihir was scripted. He was a background character with relatively little screen time and the scenes he was in were short and from a distance or at night so little detail was required since it was not going to be visible in those conditions (See Figure 03). Unlike Buckbeak or the gryphons in Narnia, Gwaihir’s performance never required him to fold his wings across his back; his performances were all aerial. “The fill eagle used for The Fellowship Of The Ring was a cheat – the bare minimum to final the shots [Aitken et al. 2004].” For The Return Of The King a much more detailed model was built because the eagle had a role requiring closer, more detailed shots. The feather setup for The Return of the King was done with layers differentiated types of feathers between “hero” feathers, feather code, and fur feathers. The hero feathers were nurbs patches and the animators could control them through the rig. The hair feathers were generated over a separate subdivision skin that was “like a sock around the original surface of the bird and was cleverly rigged not to interpenetrate the hero feathers when they moved [Aitken et al. 2004].” Gwaihir is an example of the simplified approach often taken toward wings in which there are two rows of feathers, and while this approach is adequate for the role of a background character, it may not be an suitable for more detailed hero characters.
Clash of the Titans (2010): Pegasus
The focus of the published information available on Pegasus in Clash of the Titans by Warner Brothers Pictures with visual effects by Moving Picture Company (MPC) mainly focused on the treatment of the feathers and touches only briefly on the wing. The winged horses had several hundred shots in the film and ranged in detail from background characters to highly detailed, full frame hero shots. Each feather was procedurally created, or generated via an algorithm, as curves in three dimensions. The feathers were generated at rendertime and used MPC’s “Furtility” fur/hair utility. This gave the feathers a fluffy look to them, as well as allowing the groom artist to use the same tools they already had for hair grooming. Feathers were automatically distributed across the wing, as well as individually placed and sculpted. Since the actual feathers were created during render time a rig using simple NURBS (or ‘Non-Uniform Rational Basis Spline’) surface was substituted as proxy feathers in the wings for use by the animators. With this rig, additional animation and tweaks on the feathers could be done [Leaning and Fagnou 2010].
Like other films, the treatment of the wing and feather interaction overall was to place them as two main rows of feathers and procedurally generated the rest of the feathers in the wing, therefore when folding the wings tend stack up in an accordion fashion, very evenly. This gives the wings a very fluffy look, but also a slightly unrealistic overall.
Legend of the Guardians: The Owls of Ga’Hoole (2010)
The owls created by visual effects company Animal Logic in Legend of the Guardians by Warner Brothers Pictures were highly detailed since the owls were the main focus of the entire film. This required that the wings be able to cover a wide range of performances such as flying, wing-folding, and anthropomorphic acting and and equally wide range of shots, from background to hero.
Much like real owls, the owls the Animal Logic owls without their feathers were skinny and chicken-like; all their volume and shape came from their feathers. The remiges, or main flight feathers, were connected to the wings and the animators had direct control over them; there were 24 in each wing. The animators had a lot of control over the wing and feathers: They had about 7 controls on each wing overall and another 10 to 15 on the feathers. They could rotate and translate individual feathers as well as bend, curl and cup them to simulate the force of wind [Robertson 2010].
Body and wing covert feathers were procedurally generated and controlled by the character effects team. Animal Logic’s effects team had to re-write their feather system, Quill, from the ground up. Guide hairs were hand-placed on the models and had parameters for each feather that defined the look of the feather, from length and width, to how smooth or uniform the feather is from the base to tip.
Quill also added secondary motion such as wind effects on these feathers once animation and a first pass at simulation was in place [Robertson 2010].
Animation style was also an issue due to the realistic look for the film. “We did some early tests that were a lot more cartoony: squash-and- stretch, bigger arcs, heavier anticipations, but as soon as we placed these owls in our realistic world, they didn’t belong.” The realistic style of the movie made this animations style not fit, however, Animal Logic wanted to avoid making it “a documentary”, so it became a balancing act using naturalistic animation for flying or walking, and using more traditional animation techniques for performances and talking [Desowitz 2010].