Physics Animation in Uncharted 4: A Thief's End

[Music] all right let's get this party started and we have no audio oh co thank you [Music] [Music] [Music] good morning everybody I'd like to welcome you to my first ever GDC presentation so I'm a little nervous thank you for coming at this ungodly hour

so my name is mhak I started my career in the gaming industry back in 1999 as a 3D modeler on Mafia the city of lost Heaven game luckily our company had only one animator at that time and they thought I could have a potential and I was probably decent so I I became a lead gameplay animator on Mafia 2 after that I helped vatra games with the Silent Hill downpour and in 2011 I joined the nly dox kenel as an animator so what physics animation means to us it's anything animated while physically simulated the most common implementation of physics animation is the ragle simulation basically every game today has it in some form we were already using rle when characters die but we wanted to experiment further and see if we could use it more

creatively we don't want players to notice when the physics animation is running fitting the character and natural look and feel is number one priority I'd like to show you what did and did not work on a few examples from our games but why bother with such a risky thing like physics animation when we have an army of animators right we could just brute force it and it's because we were planning on abandoning the the environments made of boxes right angles and perfectly vertical walls physics helped us with blending out of already massive amount of animations and sometimes allowed us to fully simulate something that would be otherwise a chore to implement using the old ways we wanted our characters to react more believably to whatever was happening to them our characters have incredible level of detail and we wanted to match the same level of Fidelity in animation we we also wanted players to

be able to interact with the dynamic stuff more physics ideally everywhere and because it's fun but first things first our games are running on Havoc so I'm going to use terminology specific to this physics engine although most of it applies to other physics engines as well let's start with rigid bodies these are the objects roughly describing geometry of our characters each rigid body has joints Associated to it rigid body has its mass or weight friction restitution or bounciness and inertia tensor inertia tensor describes how difficult it is to rotate an object around any given axis basically the higher the inertia tensor the more stable the object is linear damping reduces the linear movement of the object over time and angular damping performs the same to the rotation of the object

rigid bodies can be connected by constraints for organic forms of life we mainly use two types hinge constraint limits rotation in the joint to one axis typically used for knees and elbows Regal constraint is the more common one as it behaves similar to majority of joints in our bodies unfortunately both types of constraints don't behave too realistically unless we set up limits for them limits are kind of different difficult to set up every person has different natural flexibility so it's hard to decide what is The Sweet Spot I prefer more restrictive limits to prevent characters getting stuck in in weird yoga poses or this one trust me I've seen these exact poses in our game before this particular one can happen when you have too much friction on your rigid bodies and also make sure the limits are not too restrictive so play so the characters don't look like they are just taking a

nap now we have Max friction torque and it simulates friction in joints and tendons surrounding them so the rigid bodies won't flop around freely like in the video on the left set max friction torque to 20% of the mass to start out finally to be able to animate our R doll we can use constrained Motors then the regular constraint becomes a powered constraint Motors try their best to match our anim pose with maximum motor Force but we don't want them to overshoot the pose and that's why we also have motor damping another tool we have is ability to limit how fast the motor tries to recover the animation pose if something pushes it around so the right side is low speed and left side is high speed and finally we have a motor towel which is basically motor stiffness you won't see almost any difference but you

can totally feel it so yeah that's it that's all the parameters I usually tweak while I'm setting up the reg dooll there's so many parameters and all of them are kind of connected changing one often influences others too so please read the manual I know it's boring uh but after endless hours of T tuning random numbers I gave in and read the most interesting sections also check out demos provided with your physics engine they show off features in nice simplified form and if you have your own custom physics engine talk to your programmer and ask him for for for how stuff works okay here are some basic rules rules I wish I knew when I started don't try to imitate real life reduce mass of your rigid bodies by 10 to 20% for each bone going out from the

root check for unwanted collisions the chest area is so congested that it's really hard to see what's happening inside and now you can start testing and tweaking scale inertia tensors should you need to stabilize disproportionally sized rigid bodies and be patient it takes time A lot of time to set everything up but don't be too patient I'm talking from my own experience because one day I was wondering why is our R doll so floaty in the game it was perfectly fine in Havoc debug tools but super floaty in game maybe something was Lost in Translation and I spent hours well maybe even days tweaking damping on Rigid bodies and I felt like it's way way better than two days ago but I still wasn't satisfied so I went to see our physics programmer and asked him for help and he checked the game code and he

was like oh yeah yeah it's hardcoded so make sure you're are allowed to change the parameters you are trying to change anyway how do I test my reg dolls I start throwing them around basically with with the mouse that's the advantage we have as a game de developers body should unfold itself itself into a natural looking pose if limits restrictions and uh the friction and everything is set up properly the human body is soft and Squishy so tone the restitution down uh as I said before I like to keep limits on the restrictive side so if I put this guy's hand on his chest it naturally slides down next to his body and make sure you have correct friction on your rigid bodies this guy's leg could get stuck on the other leg if

the friction is too high and you might get that taking a nap pose and what I also like to do is this sitting test I think that character should be able to do to be able to sit next to a wall but it looks so cool and dramatic when it slowly slides down okay now it's time to test the regular in the real gameplay by the way uh when I was doing this for some reason the dead bodies kept reappear every time I respond the character yeah we are spooning in unch 4 so basically when I'm playing I'm trying to find out how often I can see a bad Poe this is the friction on the legs hang on and this is my arm test

the the chances to see a broken Regal are much higher when the characters are moving fast and hitting a collision holy [ __ ] so it was all physics and the limits basically held the character from breaking and one more yeah as you can see I spent some time all the there the all all the weapons anyway so we tested our R doll if it's flopping around properly but now it's time to animate it and when we talk about animating rigid bodies we talk about their states key friend rigid body which is drawn in blue color is 100% driven by animation as you can see I'm trying to move it with with the mouse but it's not possible we use key Frank rigid bodies for pinning hands or feet to other

objects we usually disable collisions on key friend rigid bodies so they won't kick the other objects to the Moon next is powered or animated rigid bodies they are drawing yellow this one is also driven by the animation but this time I can move it around by applying impulses or by colliding with other objects by the way notice how the Drake's screen left arm is flailing around that's because it's not powered and that is the third and last possible state of our rigid bodies unfortunately it's also yellow but don't worry I won't be showing unpowered rigid bodies in my presentation okay so I mentioned rigid bodies and let me briefly explain how we can do that we use so-called animation controllers and the first one is powered constraint controller which we call Simply Motors because it uses the constraint Motors I talked about earlier

and it's also shorter Havoc recommends this controller when animating dead or dying characters it's because it's working in local space so it cannot keep the character from falling without using additional tools but it produces pretty realistic results thanks to its local space nature so if you move one rigid body it moves all of its children with it unfortunately we were not able to match an animation post without using really stiff Motors and that tend to overshoot and vibrate by the way the vibrations in the video are slightly exaggerated so you can see them better and the second animation controller is rigid body controller which we call Key frame controller it's very different from Motors because it's manipulating velocities of individual rigid bodies to match an animation pose Havoc recommends this controller for live character because it works in World space and

therefore can keep them from falling due to its World space nature it has this kind of ik look so if you move for example the upper arm the hand tries to stay in place you can see the similar effect in the in the head as well but it's incredible incredibly easy to match an animation pose and the controller is very stable let me show you both controllers again side by side I also marked the key differences between controllers for you it's going to be important later and so we have this physics terminology over and let me finally show you some examples yeah I know I promised I'm Char for but let me start with the first game where we ever used our current technology for the first time and that is the last of us so this is towards the end of the

game where Joel saves Ellie spoiler alert from being killed by fireflies uh she's under anesthesia and therefore she's unconscious and Joel is supposed to carry her away from the hospital it was supposed to be a very touching moment so Ellie's arms and legs should not be moving or should be moving but not too much you know so it doesn't look comical I checked YouTube hoping for at least a few helpful videos but I was really surprised when my search return returned tens of thousands of results yeah there was one playlist that was 469 videos was crazy okay back to animation we already had this sequence at the beginning of the game where Joel carries his daughter Sarah so we decided to reuse his move set but we had no time to create animations for Ellie one idle and one run forward animation had to do it let's see it yeah it looks pretty solid

now I mean at least body it's pretty solid it's not moving at all yeah this was not shippable uh we needed a solution that could get away with limited number of animations and provide proper reactions to Joe's motion so physics right that what can possibly go wrong and there we go this is our initial setup as you can see Ellie torso and and left arm were fully key framed and not simulated at all we simulated only the right arm head and both lower legs we encountered a problem with our AET building pipeline though our characters can have only one R doll so we had to hack in this additional rll for Ellie just for this sequence okay let's check how it turned [Music] out yeah oh

yeah it's not that's not very emotional is it so yeah we tried both Motors and key frame controller to drive the rag doll but yeah shoot him okay he's dead so we tried both Motors key controller Motors work great until players started changing direction increase ining their strength wasn't solution because we needed those limbs to be loose and key frame control felt better but Loose limbs had this weird linear motion in them key frame controller is after all linear right it's in World space so okay we needed to decide between Motors and key frame controller how could we keep using motors for nice follow through in Ellie's limbs but stabilize them without increasing the motor strength is there a way to cap acceleration in

joints and we got this Revelation one and that is that standard approach is to use motors or key frame controller for animating rigid bodies but Yos our physics programmer had an idea maybe we could try both controllers simultaneously we had no idea if that's going to work or not but we gave it a try it was a delicate Balancing Act between the two controllers but it worked so we used motors with enough power to apply the animation pose but lowered their tow stiffness to minimum to make them very soft and let the limbs flop around and we use key frame controller it functions as some kind of stabilizer preventing vibrations and forcing the rigid bodies to keep the animation post when the character is not moving too

much but Ellie still kept breaking during quick directional changes and we wouldn't be able to ship without Revelation 2 and we knew that Ellie is parented to Joe's spine so yaros tried to decompose the animation post to two components local acceleration which is acceleration of Ellie's pose and parent acceleration which is acceleration of Joel's spine and now the key thing we can limit how much players's motion we apply to Havoc rigid bodies we were finally a able to cap the crazy accelerations we were getting when player was changing directions rapidly and this is from the ship [Music] game [ __ ] I I think it's pretty decent

for just one frame pose anyway so what are the key features of our Regal driving method we are Motors and key frame controllers simultaneously by changing weight between Motors and key frame controller we can achieve different results and by the way we can change those weights per rigid body and we can also cap acceleration spikes by limiting parent acceleration and how the key frame controller works for you with coding experience it might be easier to just read this it's a bit simplified because I'm not a programmer but the key principles are there we take local acceleration sprinkle it with parent acceleration then we add a little bit of velocity gain and try to match the velocities in rigid bodies and final and if the final

post is still not matching up we can finish it up with position gain and we take the resulting linear velocity and set it back to our rigid body and we do the same for angular velocities all gains and limits are exposed to our script and this is what animator sees by the way DC script is based on lisp or scheme and our programmer then leapold gave a talk talk about it here at GDC back in 2008 and it was called Adventure in data compilation so all is good I call it a success but we found out that we need one more RoR for Ellie this scene happens before the hospital one but Joel is saving Ellie again this time it's underwater and we needed slightly different parameters for our R doll much

higher damping on Ellie's arms and legs to simulate water drag and also we needed to key frame or animate different set of rigid bodies it was the right time to move the Regal definitions to DC script so I wrote a python script for Maya which exports the main parameters of regular rigid bodies and their constraints later on we decided more parameters we added more parameters for anchar 4 so we could change for example constraint limits on the Fly and what are the advantages of having reg doll in script we didn't have to touch the asset manager the default reg doll is still part of the skeleton though and I don't have to build it again should I need to add more R dolls I can just duplicate a few script lines change a few numbers and compile it it's a matter of few seconds instead of minutes although I ended up saving a

few extra Maya scenes as references for more sophisticated setups and exported regular regular settings from there which means that further tweaking of numbers in script rendered my Maya scenes Obsolete and we had no tools to sing them but honestly we this tool would be pretty easy to write we just never really needed it bigger problem is that most artists are scared to touch the scripts we have eventually decided to move everything regular related to DC script and started calling it Regal profiles so these are the building blocks of our Regal profiles and this is the real script this is the regular definition I exported from Maya there is like hundreds of lines so I collaps the blog of text down the regular definition is

hooked up in the profile here here I specify joints that are going to be key framed you know you you remember those blue rigid bodies I showed you before and this one is interesting here I specify Collision layers for my rigid bodies the script says that they don't have any collision by default but I added a set of rigid bodies that can collide with other Regals and with the environment I can add as many sets as I want and this is our baby I Define three different key frame controllers and assign them to three different sets of rigid bodies it means each can each set can be animated differently in game you'll see later why and now I'd like to show you the real beauty of our setup I can just duplicate a handful of lines in script change a few parameters and I have another possibly totally different regular Behavior but watch I can duplicate this one again hook up regular

definition with different modor settings and I have another profile so what are the advantages of regular profiles I can go nuts and create many profiles very quick I'm not limited to one character all of them work as long as the characters are using the same skeletal hierarchy and here's the big thing I no longer need a programmer to be able to test reg do in game I have all profiles in the debug menu so I can test the regnal anywhere I want I'm possibly even where I shouldn't we're done here I'm taking my brother and we're leaving you want to stay in burn with the ship you'd be my guest you got me you know what n underneath all the bravado you're just a sad little bo boy with delusions of

gr who by the way can't mess [ __ ] so long Nathan bre [Music] Nathan so now that you have a pretty clear idea how we animate R dolls and how we set them up I can finally show you the best stuff we did for anchar 4 and we start with regular vehicles I mean reg those in vehicles so we started prototyping Vehicles when The Last of Us was still in for production it was a great Proving Ground for our animation controllers and mainly for testing of the parent acceleration limit there's no better test than hitting a wall at 40 m per hour of course designers chose a car with no

roof so we can see every little detail well no detail at all actually I see it yeah it looks terrible we could probably add some lean additives to simulate reactions to Vehicles angular changes but most likely it just wouldn't cut it because we were planning on having some wild off-road sections on Madagascar so let's see how Regal handles it yeah it's way better Drake's chest moves independently on the car's seat nothing is breaking even when the car is swinging wildly let's see how we pull it off setup is actually pretty simple lower body is fully key framed and we simulate it on the spine head and arms up to hands key framing hands ensures that they won't leave the steering wheel colle are interesting we don't

have collisions on anything but spine and head we let it collide only with the seat and the steering wheel we were initially scared of letting the character collide with anything in the vehicle and we were ready to Sol it with different limits but our to our surprise spine's interaction with the seeds Collision looked very natural you'll see it later and to make your life easier I crunch some numbers from all anchar for regol profiles and try to translate them to clearer visual form I call it heat Maps the color Legend is simple two-dimensional diagram vertical axis is strength and horizontal axis is stiffness I colored the rigid bodies so you can see how the key frame controller influences the simulation remember that key frame controller Works in World space joints have their own colors and they are displayed as those little dots connecting rigid bodies I remind you

that motos work in local space and finally the grade out stuff means that the connected rigid bodies are key framed so how do you read the picture for vehicles we used strong but soft keyr controller for all simulated rigid bodies it means that the rll can follow the simulation really well but rigid bodies can be moved away from the POS even with subtle impacts and changes of momentum animation feels pretty soft overall next we can see that spine has super weak Motors but on the stiffer side they can barely support it having soft spine allows for nice compression in the spine although it needs to be held by strong and stiff arms otherwise it would compress too easily it's actually interesting how much the arms influence the final

result they make Drake look like he's fighting the steering wheel the side to side swings are Wilder and have more natural angular Motion in it on the other side the weak arms make the side to side motion feel too linear thanks to the majority of influence coming from the key frame controller and the right side feels too mushy and lifeless to my taste driving 4x4 should feel wild and exciting and let me demonstrate the effect of parent acceleration limit one more time the red volumes you see in the video demonstrate an animation pose before simulation this is how our characters would be moving without physics and so what the parent acceleration limit can do for us it prevents transferring too much acceleration to our ragd doll and therefore breaking it a real person would be thrown against the dashboard with these impacts also notice how Elena's spine bounces

off the seed when they Collide thanks to this feature a r doll can handle anything but it doesn't mean it's always the best tool R doll is good for small bumps and realistic weight shifting but we use full body animations with no rag doll for the heart hits so what I watch and I'm going to put yeah so this hard hits and by the way our programmer Edward Pereira is going to talk about off-roading in AAR 4 in this same room today at 2 p.m so you can learn how he pulled pulled off the physics of a car and stuff oh yeah I was driving recklessly a little bit okay let's talk about something entirely different and that is player climbing one of the main goals for the climbing

mechanic was to give players a very analog and organic feel the same feeling the real rock climbers have when they search for the next handhold on the sheer rock face while balancing on their feet wow it was complicated it looks like a ballet our characters were always climbing these perfectly ver flat vertical walls but we wanted to to move away from that we wanted to climb slabs and overhangs and when the overhang becomes roof Jake swings his legs and PS through that section thanks his thanks to his enormous upper body strength and when he's not climbing these impossible rocks you can find him hanging out on a big ass truck speeding through the countryside of Madagascar and to do all that you need crazy amount of Animation just to make the player reach for the next handhold requires dozens of

reach poses basically every cross-section on the spider web is a pose that has to blend well with all of its neighbors in the game they constantly blend based on players input and once the player reaches the next handhold we played a short transition animation it's really hard to keep all animations consistent and we kept seeing a little hitches in players motion we thought it's a great opportunity to physics simulation you know to smooth everything out and this was our early prototype notice how the left side is quite a bit noisier than the right side where the Regal is running and this was recorded from the latest build as you can see our animators did an excellent job and animations blend much better but can you tell which side has the Regal

running okay hands up who thinks is the right side wow 15 people 20 yeah you are correct is the right side I'll show you why yeah there is this very very subtle difference the Regal adds this nice subtle overlap to Drake's butt and the character on the left side just kind of eases into a post after each move you would totally feel the difference on the stick though it it feels very different here I slowed it down for you so you can see better the difference between animation drawn in red and final result everything is happening so fast that you can barely see a difference but you can totally feel it while

playing and setting up the climbing Regal was a real challenge I wanted to crank the softness in Drake's body up for added momentum and nice overlap but I had to be careful not to introduce hyperextensions in his arms basically everything was tailored to the worst case scenario and there was climbing on Dynamic objects here we have the heat map again hands and feet are key framed to ensure proper contact with the environment and also noticed that I key framed the forearms as well we needed arms and upper body to be super strong because they carried most of the body weight spine was pretty weak to allow the overlap and legs were almost unaffected by the key frame controller but were powered using Motors in joints you can clearly see that the upper body is firmly controlled in World space thanks to key frame controller and it's its

effect tapers down towards the legs and legs are animated by Motors almost exclusively in local space and here's our test for the climbing rag doll dr's body reacts naturally to impacts coming from the truck moving the lower body in a nice springy fashion okay I'm going to let it run one more time that basically every time the truck does this big bomb tra's body nicely does this think okay but we had some really sharp Corners in our game and the rll got sometimes stuck on invisible collisions so we tried to disable the rll collision and we saw no side effects occasional clipping is way better than this and this is my favorite part it's the

Hang climbing player can climb or jump to a hang position under totally arbitrary angle this is how our early prototype looked like yeah it's pretty terrible it's basically just a blend into a hang pose but before we committed to creating millions of different Landing animations I gave the Regal a try I created a new profile with super loose lower body and Drake swings around properly when he lands in hang position but I quickly realized that this profile looks great when Drake is just hanging but it felt too loose when Drake tried to actively do something so I created a new stiffer profile for hang reaches the thing is we switch reg dolls in code based on player state so no R dolls most of the time driving reg in vehicles climbing and now hang timing but we had two profiles for one

hang State and I got an idea to use our animation event system which we simply call effs for enabling and disabling regular profiles we like scripts so it's just a text file with similar syntax to XML but it's really simple and most of our animators have been using it already for triggering events like weapon reloads particle effect effects and sounds and I was excited I couldn't wait to test it out I recorded a slow motion video of Drake jumping down to hang and moving side to side next to his fee is a debug draw with the name of currently active Rango profile with its blend value stiffer regular fades in every time I press the left analog stick and when I release it the looser version takes over again if I go side to side these two profiles keep blending in and out constantly and dr's momentum carries over each move so I can make him swing

more and more every time I change direction it feels very organic and if I was doing like left and right left and right basically those two profiles will be constantly blending in and out so sequencing of Regal profiles gave us full control over when and which Regal profile to use with frame precision we can also control how quickly Regal fade in and out and yes we can blend between Regal profiles seamlessly this started the Regal Revolution Regal started appearing everywhere in the game but it also gave animators more responsibilities because once the Regal profile is enabled it's going to keep running until you turn it off again it was extremely difficult to safeguard all possible transition Transitions and we kept seeing player

running around with the Regal enabled all the time no no don't worry it's it's fine yes so to fix this we introduced a simple rule game keeps the regular profile running only if the currently playing animation contains a event this feature still allowed us seamlessly sequencing of different regular profiles but it also made sure that we don't run regle where we don't want to you know no regle is better than broken regle and correct waiting between key frame controllers and Motors was crucial for hand climbing arms were holding almost the entire body weight it quickly tapers down down towards the spine and it has almost no effect in the legs it's used

only to stabilize vibrations moreal forces and stiffness were cranked up in the spine to hold the pose of the lower body the stiffer Regal is just a slightly modified version of the looser version more of the body is held in place by the Keir controller and also the legs got a similar treatment to lift them up more by switching to a stiffer profile we are basically simulating muscles putting more work towards reaching the next handhold unlike the regular climbing roll this one had collisions enabled and I'd like to show you why it's because the handang Climbing doesn't mean the player is just hanging down free of any obstacles in this case Drake's whole upper body would sink into geometry should he have no Collision the side effect is that his chest can push the Dynamics objects around

and I'd like to show you one more video demonstrating how seamless the transitions between hand climbing and regular climbing are I also poked the cage with the mouse in this video so you can see how everything's reacting naturally somebody should make a game where players are finally allowed to do this type of stuff okay now onto a more explosive stuff every Uncharted had a Chase s Chase sequence and of course unch 4 is no different Mad Max came out no long before we started working on our Chase sequence we loved how the crashes were staged so well perfect angles perfect motion and timing was really amazing but how could we achieve similar thing in in a video game and we started with animation we decided to have a maximum of two people per vehicle we had to account for each character being killed in individually or together

and no they don't just freeze at the end of Animation we physicalize them so they keep moving without being animated which is actually not entirely true I did this test to see how we could animate characters without actually animating them when I killed the guy he plays a very short death animation and then Blends into one single pose which he holds using regular Motors until he stops Under the Stairs I learned how critical the pose is for smooth rolling motion arms need to be close to the body legs pretty straight the more the shape resembles a cylinder the better also proper friction on the regular played a big part I used all this knowledge many months later when I was begging a programmer to implement this you know you need a lot of arguments to sell the idea to a programmer so let me show you my death animation

again notice the cylindrical rolling pose and this is how it's in the game it worked pretty well although Regal have a really hard time to keep the pose intact when they hit the ground at 50 mph one little bump on the ground and the pose turns into a mess we use the similar system for off-road vehicles so how do we animate the vehicles the conoy vehicles are following a set of splines based on what the player is doing it's all scripted by our awesome and designers and once the driver dies or the vehicle is damaged enough we trigger a death we disconnect the vehicle from its

spline we store its last moving vector and we play the animation along the stor Vector using the key frame controller yes even vehicles are running physics animation we use pretty stiff key frame controller so the simulation matches the animation the best it can and why are we running a physics animation so we can animate our vehicles until something really bad happens and it happens sometimes that our object hits a small bump and moves away from the pose we measure the distance between rigid bodies and the animation posst every frame and when the aor distance becomes too large we Fade Out the key frame controller it normally doesn't happen because after Small Bump the key frame controller can recover the animation pose easily and only a major Collision could stop animation from playing and the major Collision is usually player smashing everything with his car

which is the biggest advantage of the system we always get a better performance than just letting the vehicles explode randomly and it's pretty safe to use as a bonus the key frame controller snaps the animation to the ground for us the only thing that I don't like about the system is that the objects might Jitter a little bit when they are being pushed too far away from the animation po but the key frame controller haven't turned itself off yet but I think we could fix it if we were given more [Music] time okay and we have this epic cinematic moment when you take over the [Music] Jeep yeah even the truck was animated uh with physics animation okay now onto the boat

chase it's an opening sequence of our game Drake and his brother Sam are being chased in their little boat on a stormy sea by guys on speedboats and other guys on big boats and they throw mines at our poor little boat you should play it's it's really fun so the sea is really bumpy and our little boat is widely moving up and down and side to side while Sam is in the back of the boat trying to shoot the guys I tried to simulate The Bumps by baking into animation but you could tell that s's body is not moving in sing with the sea this video is from final game when we run physics on Sam we key framed Sam's hand and feet to pin them down to the boat and we let only the the right arm collide with the boat you know to prevent clipping when he's aiming

Sam's aim poses didn't have any instability baked in so I let our animation controllers work really hard and simulate it for us Sam's whole body has pretty soft key frame controller while Motors were basically holding the animation posst for us I stiffened his right arm a little bit more in World space using key frame controller so he could aim better and did the same for the head so it's not bobbing around we wanted Sam to feel sharp and aggressive and not sleepy similar to the Jeep we disable rll for the big bumps where the same falls down to the ground and use it only for small bumps and weight shifts it was super easy to implement with our animation event system and this sequence is a prime example of how we used rle as a really simple post-processing tool Drake is being dragged behind the

truck on a rope and going really fast and he's desperately trying to reach it you can steer Drake side to side you can make him climb the Rope up and down all this is happening on a pretty bumpy road so his legs kept clipping the ground quite a bit we tried to use a r doll to fix it the profile is super simple everything except his leg is key framed and the legs are trying to match the animation 100% by the way I zeroed friction on them for better stability let me step through a few frames to give you a better idea of what was happening by the way the big blue ball in front of Drake is a special Collision for simulating him breaking boxes and fences and other stuff with his head so as you can see not much is really happening it's just a subtle adjustments nothing

big until now look how deep under the ground this leg is but you won't even notice until you see the debug draw and this is my last example uh first let me explain what ing game cinematic is it's a sequence in a game that looks like a cinematic but it's in some way interactive in this case the Jeep is dragged by a Wild River while spinning around and boun bouncing of the Rocks but player can still steer it a little bit again something out of animator's control is moving our characters and we' like our characters to be reacting to what's happening to them so we naturally reached to physics it was towards the end of production and we already had nearly 40 different regular profiles in the library thanks to our eff system it was super

easy to pull off so we run the classic vehicle rll on both characters at the beginning of this scene but once the vehicle lands in the water we switch to a custom rag dooll it's a slightly modified version of Sam's Rego from the boat chase there we can climb up this rock on it and this is where it transitions to other gameplay look how far Elena's body is from the animation pose I drawn a yellow outline around her body so you can see it better it took me less than 30 minutes to create a Regal profile and hook it up in the animations we also used Regal in the following epic cinematic [Applause] moment no Panic no Panic I am see that Sam is running Ral well all characters

are running Ral it's because the Jeep is still kind of steerable on the Rocky Face so we don't know we we cannot just bake the reactions into the animation now it was the hand climb and get us out of now you can see that Sam is praying for more Rego it's like very very subtle details but it makes a big difference when you see such a detail scene visually and something is a little bit off so none of the stuff I showed you today would be possible without stable frame rate luckily our team has some of the best programmers and artists in the industry and they were able to optimize the game 100% but nothing was perfect it was really difficult to synchronize all procedural anim systems in the game animation blending ik step physics step

we were quite often working with obsolete data from previous frames and yaros our physics programmer had to write some complicated predictive algorithms to fix that unfortunately this is way beyond my expertise and you have to ask him should you have any questions I also found out while I Was preparing this GDC talk that I knew quite a lot but still very little about our system I I've learned so many important details which I had no time to learn during production but now I'm ready to make everything in our next game better and that's [Applause] it thank you thank you very [Applause] much okay any questions we have hey how's it going uh great talk thank you thank you I'm curious if you've used this system in a

purely combat context cuz it sounds like a great way to get uh better performances in like a fist fight but physics and compat as a designer really scares me so I'm wondering if you guys have tackled that physics in combat uh what do you mean by physics in combat so if I get like hit in the sternum versus the left shoulder so like hit reactions exactly uh we used a ragor only for death reactions and we used animation for for for the for like those little hit reactions but we yeah experimenting with it it works it works all right thank you but not yet not not in ACH for okay so uh Havoc provides you the previewer for rag doll setups and other physics uh object designs in Maya but assuming since you have all the DC script script and EFS uh-huh did you end up using those previews I assume the

ingame previews were more convenient and actually reflecting the the final implementation but yeah I basically use the the the debug Tools in Maya only for like previewing limits and frictions in in the joints and then I I went to our game and we have all the tools to test regular there so yeah as expect only limited use then yeah yeah but those AOC tools made my life easier when I started setting up the reg they are really really nice had the same experience so thank you sure okay anybody else uh I put some business cards on each side of the table so feel free to take them and you can just email me when you are fresh and not overwhelmed by the amount of information and if you want come close and we can talk about stuff for