A skeleton for a female assassin in Assassin's Creed would take "a day or two's work" to create, rather than a replacement of more than 8,000 animations, according to Naughty Dog animator Jonathan Cooper.
Cooper previously served as the animation director for Assassin's Creed 3; prior to that, he worked as the lead animator for titles such as Mass Effect 2 and Deus Ex: Human Revolution. He left Ubisoft to go work on Uncharted 4.
The animator took to Twitter in response to recent comments from Ubisoft on why female assassins were not included in Assassin's Creed Unity. In two separate interviews with Polygon, Ubisoft developers said that female assassins were originally planned for the game's co-op, but were cut due to "the reality of production."
"It's double the animations, it's double the voices, all that stuff and double the visual assets," creative director Alex Amancio said at the time. "Especially because we have customizable assassins. It was really a lot of extra production work."
Level designer Bruno St-André estimated that to create a skeleton for a female character, more than 8,000 animations would have been necessary.
Speaking to Polygon via a phone interview, Cooper said that skeletons for female characters are typically not that different.
"I think what you want to do is just replace a handful of animations," Cooper said. "Key animations. We target all the male animations onto the female character and just give her her own unique walks, runs, anything that can give character."
According to Cooper, the model's facial animation would be additional work. However, he said it would be possible to use temporary solutions and replace them later.
"You can quite easily put male animations onto the female character, and it can still be good," Cooper said.
Assassin's Creed 3: Liberation heroine Aveline de Grandpré got many of her movements from Assassin's Creed 3's male protagonist, Connor. Only a handful of her animations, such as walks and runs, were replaced.
"The games were made in parallel," Cooper explained. "Pretty much, you're just taking Connor's animation set and replacing key animations.
"They do some really clever stuff there. For example, Connor uses this tomahawk during a fight, and they actually gave her a weapon that was similar in shape to the tomahawk, so all the animations would work on her without having to change them at all."
He added that the process doesn't work the other way around, as the male character then has a more effeminate set of movements.
Cooper spoke briefly about the success BioWare's Mass Effect series has had with its swappable male and female protagonist. Although voice acting and facial constructions were extra work, the game uses similar or the same skeletons across both genders and all its races.
"We made sure that their skeleton was identical so it could be shared across everything," Cooper said. "I think maybe the female had shorter arms or something. We might have also replaced some animations like holding a gun or stuff, but otherwise they're just shared across all the characters, all the different races."
According to Cooper, this practice isn't unique to Mass Effect, but several other projects he's worked on as well.
"It's the same on the [Assassin's Creed 3] build," Cooper said. "They share animations. I think the assassin shares lots of animations with NPCs as well. For Connor, I know we gave him some of his own unique jumps and kind of things to give him a lot of character.
"It's something you have to consider when making a big game. You know not to do unique animations for every single character."
There's a danger in creating characters that are too homogenous, he said, but even in directing mo-cap there's an effort made to make sure nothing "stands out too much." Key animations help infuse characters with personality later.
"It's not the best quality," Cooper concluded. "It's definitely a compromise in quality. But I think it's more important that you can actually play as who you want to play as."