Bare Butt Boxing uses procedural animation to bring its characters to life. You have probably heard of the term "ragdoll" before, one of the most common use of procedural animation. It's a satisfying physical reaction that usually occurs when a character dies or gets knocked out. The character will switch from a normal "animated state" to a ragdoll state and fall down in a physical way, based on the position of their limbs and the force of the impact. Bare Butt Boxing uses a different kind of procedural animation called "active ragdoll". This technique uses the same principle but keeps the character in this ragdoll state permanently, not just during death. Various forces and constraints are then used to keep the ragdoll upright and animated while still reacting to all physical forces.
Early active ragdoll prototype.

Constructing the Ragdoll

The ragdoll is constructed from primitive objects like cubes, capsules and spheres that approximate the dimensions of the body and limbs. These primitive objects are then linked together in a hierarchy so that motion of one can affect the other. For example, if the upper arm moves, the lower arm will follow. Primitives are also constrained so they don't exceed certain rotation angles and maintain desirable properties like stiffness and bounciness.
Fishy's ragdoll setup, 13 main primitive shapes are used to construct it.

Active Ragdoll Benefits & Compromises

Compared to traditional animation, the active ragdoll approach provides some unique benefits. Animated characters require a wide variety of animations that blend between each other for a character to feel right. In contrast, characters in our game require no animation at all! All motion is derived procedurally and the physics engine of Unity takes care of the rest creating endless possibilities. Such a degree of automation introduces unique challenges, however. A lot of careful consideration is required to create stable, relatively predictable behaviour because physics can produce unexpected results. Luckily, surprising behaviour is often part of the charm of physics based games like Bare Butt Boxing!
All characters and bodies in the example above are procedurally animated with physics and they all constantly react to each other. This kind of complex behaviour is impossible with traditional animation.

Physics and Multiplayer

Physical simulations add many unique challenges when creating a multiplayer game. For an enjoyable multiplayer experience, low latency is required. Any delay between a player pressing an input and seeing the effect of their action in the game can impact the experience negatively. This delay happens due to the players' computers (clients) requiring to "talk" with each other and exchange data. When player A presses the jump button, this data needs to travel to all other players to see player A perform the jump on all their screens. Active Ragdoll characters exacerbate this problem by vastly increasing the amount of data that must travel between clients. Technically, all the rigid bodies (the primitive objects we've covered before) need to be shared between players. If we do some quick math, let's assume 13 rigid bodies per character, in a match between 6 players, that's almost 80 unique objects to track just for our characters! In Bare Butt Boxing we solved this problem by only passing a limited number of key rigid bodies between clients and simulating the rest on each client locally. Multiplayer is an incredibly deep and technical topic so this only scratches the surface. Under the hood, advanced techniques such as client-side prediction and server reconciliation enable very low latency multiplayer that keeps everyone happy!
One of the most common and frustrating examples of latency is players existing at different levels of delay between clients. Hope you enjoyed this brief technical dive into the active ragdoll technology at the heart of Bare Butt Boxing! Thank you for reading and stay tuned for more! Tuatara Team

[ 2022-11-09 15:44:49 CET ] [ Original post ]