Perhaps the biggest differentiator between the AC and other open-world games is the free-form navigation allowing you to explore all areas with an unrivalled mastery of your environment. As such, this was a core area we looked to improve upon.
The image below, entitled “Battle Charge” is, for me, the iconic look of Connor. While not on the box cover, it perfectly captures the last thing a target would see before being assassinated – a thunderous man bursting through the trees to run you down.
The pose he’s in is a frame from the very first animation to change in the game, the sprint-impulsion, seen every time you accelerate to a sprint. In order to populate this kind of iconic posing elsewhere throughout the ground movement system, we were very fortunate to have the help of Ubisoft’s Technology Group. To this end, we doubled-down on physics as our supporting technology to aid the animation and help solve our dual challenge of improving the responsiveness of the player character while still maintaining his weight.
Above, you can see a video of lots of physics programmer Simon Clavet’s preliminary investigations right through to the final result. We were fortunate that we could cherry-pick what we wanted, as much of physics involving ragdoll leaves the character reacting to external forces and ending up looking rather silly. Instead we chose to focus on his anticipation of the undualting terrain as well as when he twists and turns while changing direction.
With wide open streets and the vast North American frontier there was to be a lot more running in this game compared to past entries. By breaking down reference taken from our own mocap explorations, we recreated this snaking shape of the sprint impulsion with foot-locking, two 8-step cycles and two leaning cycles blending with procedurally modified feet placement to anticipate turns and shifts in weight. I believe we will have a much greater reliance on physics in the future of videogame animation, and this first foray into that world provided a lot of insights – not least as to how difficult it is to tune – but the effects are well worth it in my opinion.
We knew it would be big if we could pull it off, but all the time were terrified it would turn out looking like Tarzan. As such, we established rules such as no rope-swinging and limited monkey-bars, with Connor running along branches as much as possible to avoid constantly jumping and swinging. To achieve the varied style initially set out in the Target Game Footage, several new moves were created to cover the proposed variety of tree styles outlined below by the art team.
V-Shapes: A series of poses adjusted by IK to cater for any possible angle of trunk or branch the Assassin might rest in. This also included jumping between them with all possible angles catered for.
Trunk-around: Giving rise to moving swiftly past a central trunk, allowing the Assassin to run along two branches of any angle and height difference.
Monkey Bars: The ability to use one or two-handed swings between branches of any distance, with no more than three in a row.
Jump Variety: This was a big one – replacing the previous jump system with a new style focussed on variety was a major undertaking given the sheer number of animations involved.
The old jump system above, jokingly entitled the Full Body Emotional 3D Targetable Jump System, used a parametric-blending approach to blend between animations covering every kind of distance available to the player. However, parametric blending requires very similar kinds of actions in order to blend correctly. If we were to add variety to the jumps we couldn’t simply replace the animations.
After many months of prototyping we settled on a hybrid system, separating anims into groups for height and distance, only blending between similar actions. Below, the blue distances were all similar, while each of the further orange jumps were played alone and simply stretched out. The reds contained pairs of similar high and low jumps that would blend depending on height but were unique per distance. This setup, combined with agreements on the level-design side to mix up distances and heights as much as possible, gave the variety that enabled Connor to seamlessly traverse the trees while rarely repeating the same jump in sequence.