hi my name is Alexander rudenko I'm a lead gameplay animator and today I want to talk about physics and animation my journey began at bansai games the very company that developed cascader software for animation I worked there for 2 and a half years and since then I have grown to love physical animation very much if you check out my works you'll see that almost all of them lean towards realism they are exaggerated at times but look believable enough so when you watch them you believe that this character could indeed move that way and all thanks to the understanding of the physics of motion when I joined Bonsai games it was initially very challenging for me at first because their standard for animations was very high it was impossible to achieve it right after school it was like an invisible wall you kept bumping into not quite understanding why you couldn't move forward I still remember my first animation there was a project with three factions strong agile and precise the strong one was all about physical strength the agile guys were more of acrobats and the precise ones were assassin likee so I had to do a jump for the precise I worked on this single jump for around a month I was very surprised they didn't fire me I am still very grateful to my mentor who didn't give up on me thanks alexe if you look at my first demo real that I used to apply to the studio you'll see right away that the level is a bit low for a studio that is strongly focused on physicality so when I got more or less used to their software cascader and my understanding of Animation improved I started to practice in my free time using references I could find online and create some personal Works here's a quick example basically it was rotoscoping where I just copied the movement and calibrated my eye in this regard cascader helped me a lot there was a slightly different approach to the rig and interpolation there was also a cool feature that allowed me to track the center of mass which was set up for each character in the end I made some animations that greatly Advanced me in my understanding of the body mechanics and physicality in general this by the way is the answer to the question how to become better as an animator the answer is simple you need to animate more well ideally also with feedback from a more experienced animator so that they can point out and explain the problem areas in your animations today I can highlight several key components of a good animation in my opinion these are the center of mass rotation speed inertia of body parts and arcs let's break down each element starting with the center of mass the center of mass is an abstract point that shows the distribution of mass within the body in simple terms it's the body's midpoint this point provides us with the information on how speed is dampened how velocity is gained how a character Falls or stands stably and whether an object rotates correctly or not the concept of the center of mass is quite extensive but I'll try to briefly out outline its key aspects using examples we have a character with a center of mass set up how do we set up a center of mass it's actually very easy you simply insert locators into the character's body into joints you insert them into the middle part of each foot then into the middle of The Shins into the middle of the thighs and into the controls of the pelvis and the chest control then we continue with the head shoulders forearms wrists and the same on the other side all of this is created inside the joints then we create another separate locator which will be our Center of mass now we constrain this locator to all the locators we created with Point constrain then we have to set certain values for this locator I set these values roughly here I put the weight of the body parts I used some image took the values from there and rounded them to avoid figures like 0.9 this way they would be more evenly distributed and looking at the result I can see that it works quite correctly I decided to work with that I didn't try to achieve very high accuracy because it's not important for our demonstration also the map itself introduces minor errors my main goal is to show you visually how it works I don't need to make absolutely accurate Center of mass so now we have the center of mass ready and we made sure that it works here I also made a vertical line a simple cylinder which shows where the center of mass is on the ground and on the ground I created a small plane that would be always located between the legs to see how the center of mass is positioned in relation to our support points support points are essentially our legs or more precisely our feet I thought I'd show you how to make such a plane that follows the feet as well you can see I move the foot and the plane follows actually it's just skin to a few bones let me show it what you do is you create a Joint inside create several joints like this create a plane your plane will have your Dimensions I set mine to six I kept a low number of polygons because it's not really important and here I specify 3 three that's it I've created a template now all I need to do is Select these joints select the plane go to skin and here I choose selected joint and press apply now the plane follows the joints it just somehow skinned itself and it's good enough for us right so here I have two moving cubes and I want this plane to follow them I create locators in the cubes move these locators here move those locators there to the edge of the foot as I had it I can even shift it a bit to the side and all I need to do is just constrain my locators since I created them inside the cube these locators and all I need to do is constrain them with a point using only these two check marks not all and without keeping the offset I simply press constrain that's it now my platform or rather my plane will move along with the foot if I don't lift it nothing will happen but if I move it in different directions it will follow my foot and show the area located between my support points our Center of mass can help us understand how balanced a pose is as long as it remains within the area between the support points the character is in balance and won't fall but as soon as the center of mass moves out of this area we start to fall if we don't support it with a support point we'll fall here I'm warming up stretching a bit then I start swaying left and right and as you can see when I sway the center of Mass doesn't move beyond the support Point here I almost fell here I'm also close to falling and now as you see the center of mass moves beyond the support point when it was between the support points it still somehow worked but as soon as it moves beyond the support Point that's it I start falling so what am I doing here I try to put my foot down to catch my weight otherwise I'd fall there will be another example now where I'll fall see if I don't put a support point I just fall understanding how balanced a pose is under normal conditions is very easy if for instance I stand in a certain pose I can align the support points into a single line and see how balanced the character is I have a special pose prepared here this pose is quite Dynamic but the question is how balanced is it if we look from this angle everything seems fine but when we switch for example here something looks off we see that our Center of mass has moved out of the balance Zone where the center of mass normally is when we're not falling the character is visibly shifted in this direction this indicates that she will most likely Fall to solve this problem we simply shift her backward so that the center of mass is between the support points different ways to easily do this another easy way to do this is to Simply take a vertical line approximately from the support point we deliberately align them draw a vertical line upwards and look at the approximate distribution of mass if we see that the shape on the left looks similar to the shape on the right then we say that the pose is balanced there's a feeling that the character still falls back slightly but if we adjust it like this then the balance will even out again I talk about the volume of these two parts on the both sides of our vertical line if we see that the volume on both sides is similar we can say that the pose is balanced but but in fact all this can be considered a balanced pose while it's within the limit of our plane so the closer we are to the edge the harder it will be for us to stand the more likely we are to fall and for example when we stand up we also throw our Center of mass look at how I push off what am I doing I push off with my hands giving speed to the center of mass the center of mass is thrown onto the support point and continues further and then I just move it and place it in a comfortable position for me again what happened I fell pushed off myself with my hands the center of mass accelerated and crossed into the zone between the support points I caught the balance here meaning you can see that my center of mass was going one way then I caught it moved it back and stood up in my usual pose in fact balance can also be seen in other situations for example like tight rope walking here you can see that many guys walk without safety harnesses apparently they got an A in physics at school since they are so confident well let's probably look at another example of how we can maintain balance we can not only stand on two legs we can also stand on one leg and when we stand on one leg our balance or rather our Center of mass must also be kept above the support Point since we only have one support point the plane I made won't work for us anymore so we have to keep our Center of mass over One support point you can see that the center of mass moves slightly which means the center of mass is never in a static position throughout this movement I try to catch the balance I keep the center of mass within the range of my foot the last example on the topic of the center of mass balance this is me trying to do a handstand I mean I was trying to stand on my hands but I couldn't do it properly because I have almost no experience in this and as you can see I constantly move my hands but I can't stabilize my balance and stand still I always end up just moving my hands you've probably seen the same thing in little children learning to walk initially it's very difficult for them to stand and they constantly try to balance they are constantly trying to catch their balance meaning trying to stabilize the center of mass but it's very difficult at the beginning and after a certain number of repetitions they eventually acquire the skill of balancing on their feet everything in animation is like in life the more attempts you make the better you get all right let's move on we've covered a subtopic of the center of mass balance and the next subtopic of the center of mass is the rotation of the character if we look at my animations there are actually a lot of rotations there and this honesty and credibility of these rotations are achieved by the fact that they occur around the center of mass it's a key point that all objects rotate around their Center of mass for example we can consider such rotations in figure skating look this girl is rotating around her Center of mass we can easily pause the video at any time draw a vertical line and we'll see that her Center of mass is right here maybe a bit to the right somewhere around here probably if we try again to outline the shapes we have here and here we'll see that they're roughly the same in terms of volume this indicates that the character is at the center of mass meaning the character is in Balance if we look at my first demo reel you can see I had issues with the center of mass here I have some acrobatics animation I always liked it but initially undoubtedly doing it without the understanding of physical basis was very difficult for example looking at this rotation here you can see that the character is rotating around the pelvis not around his Center of mass because his arms are heav offset they are massive but they rotate around the pelvis and this doesn't work correctly so it's very important to pay attention to these things and understand how they work the rotation around the pelvis as you've just seen is the most common mistake that many beginner animators make when working with rotations it's understandable why it's done this way because it's the easiest way but we don't always rotate around the root control but around the center of mass it's important to remember this fixing such things is very simple in school I recommend to beginner animators for whom creating a center of Mass is like a 20-minute adventure to create a locator and place it roughly in the character's Center of mass if for example we take this character I simply create a locator and move it to the approximate Center of mass right here now I rebake animation on the new locator and just zero out all the translates now the character rotates around their Center of mass it's quite simple for example look at this guy who jumps off the bar and then lands here we'll see that his pelvis moves nicely along a ballistic curve but what we need is his Center of mass moving along the ballistic curve not his pelvis so we move somewhere here we create a locator roughly in the center of mass it doesn't matter that it may move incorrectly somewhere in the beginning or in the end our task is to fix this most difficult part with the rotation if we look at the center of mass now we'll see that it doesn't really work well what do we know we know that during the flight the speed is linear so for example from here to here I'll delete all the keys I'll make the speed and space linear I won't go into detail why it's linear because it'll take too long now let's work on the flight itself I look for a part that I'm satisfied with like this Frame is good already we delete all these Keys here starting from this key we can delete let's see deleted now we refine the ballistic curve as you can see this is fixed very easily not everything works well like it doesn't rotate much here but rotates a lot here but that's another matter in general fixing such things is super easy if you know what a center of mass is and remember that character rotates around it now let's discuss the next point in our section about the center of mass this is acceleration and deceleration when moving a character we usually see how their Center of mass changes position if we look at this example we can immediately see how the center of mass works it's important to track this Center and understand how it should move but in general the rule is very simple the center of mass cannot just accelerate on its own nor can it simply decelerate in order to accelerate support points are necessary for example when we stand on two legs we accelerate to the right and to the left as we can give speed to the center of mass and it's the back leg like a spring that propels us forward it's during its contact with the ground that we gain speed as you can see I'm squatting a little this back leg turns into a spring that I simply release and start running here for me it's super easy but if you consider the scenario where I try to start on one leg it becomes much more difficult it's not possible to accelerate at reactively like that you have to transition your character into a fall which means we shift the center of mass forward and once we do it we start falling actually any step is a fall we always catch ourselves on a leg and running is also a fall as you can see it's not possible to accelerate reactively like that although I tried here I managed to squat I started the fall but I couldn't push off properly since I was lacking the point of support behind me which should have propelled me forward right here I position my leg on the opposite side jump on this leg compress it and by releasing the leg I gain speed this works like a spring another important point is how we can decelerate the center of mass for this we need a so-called stopper pressing with the leg according to the direction of the center of mass movement this means that if you don't extend your leg forward you simply won't be able to stop that's exactly what's happening here I'm running trying to put my foot forward but since I'm stepping before the center of mass and not according to its movement I simply stumble and fall it's impossible to stop like this I tried a few times and every time I fell I just can't stop I tried to extend my right leg forward but I didn't tense it so I just stopped moving my legs and fell thus if you want to stop you need to extend your legs forward and lean your body back a little now let's see how it works I gradually start bringing my legs forward and since I'm not tensing them too much I have to take a few steps I lean backward and I slow down the speed of my center of mass the same here gradually by moving my feet I slow down and the last option is when we really extend our leg and tense it and in this case we sto sharply without any problems and here at the last moment I extended my leg much further and squatted very strongly again the analogy is the same as in the beginning of movement we discussed before I squatted in order to start and here I squat to slow down to press my center of mass a bit closer to the support Point all right we finished a large section on the center of mass and now we're moving on to the rotation speed this one is simpler to understand if we're talking about physical animation or pseudo physical animation then rotation in a static pose and flight remains constant unchanged as we saw in this example so essentially this is how we rotate if we consider real conditions there is still air resistance and it slightly slows down our speed but to make things easier this aspect is always omitted and it's assumed that rotation is not affected by air resistance if we consider rotation on the ground then the friction force will come into play and because of it we will slow down let's first consider figure skaters we've all seen their performances but let me show you a video sometimes they reach incredible speed when spinning why does this happen the answer is fairly simple the closer we compress to our axis of rotation the faster we spin the further away our hands and legs are from the axis of rotation the slower we spin the axis of rotation as you might have guessed passes through our Center of mass if for instance we divide the character as I've drawn before then approximately the left part should be equal to the right part the leg makes this circle so the leg doesn't stay in one place it's actually trying to compensate for this slight displacement we can see here one part is slightly bigger than the other that's why the leg draws this circle it's like it's not rotating on the toe like a ballerina if you look ballerinas rotate and their toe stays in one place it doesn't move but if we look at figure skaters there's always a small circle drawn by their foot I tried to simulate this rotation and attempted to record something similar I couldn't spin for very long but I think for the sake of example for clarity we can use this one when I spread my arms in different directions I spin slower when I compress I noticeably speed up this can also be seen in the graphs you can see slower rotation here and the acceleration happening here just when I bring my arms close to me I accelerate it's the same here a more gradual speed and here it's faster also here it's visible why I couldn't spin for long I couldn't keep the center of mass above the support point my leg slipped somewhere to the side and I started falling and every time if you notice the same thing happens here my center of mass starts wandering starts moving to the side or my leg starts moving to the side and in the end I can't catch my balance if I could stabilize my center of mass above the support point then I could spin much longer this takes us back to the hand standing or kids learning to walk practice practice practice is what's needed if you practice then you'll be able to stabilize this and I'll show you more rotation in the air changes in speed and the rotation depending on the pose the character takes all of this is quite conditional generally nobody will ever demand this level of accuracy in games such precise angular speeds from you your task is simply to understand how it works and nothing more here it's visible that the character rotates around their Center of mass but if we look at how the center of mass behaves more precisely its projection we see that it moves back and forth this too again can be easily corrected what do we do we just take a snapshot of our Center of mass basically we take the information from it that we'll use to fix the center of mass we see that the center of mass wanders quite a bit then we simply take all our translates here we only have the pelvis knees and feet among the translates we take these five controls and bake them inside this locator this across button basically does it through the locators and after that we simply delete the translation same as before there our character with a perfectly stabilized Center of mass rotates physically correctly the center of mass doesn't wander anymore here it's visible that in reality I didn't quite correctly make the center of mass here when it rotates I see the larger part appearing in turns on the left and on the right but this is exactly because when I made the center of mass I made it very roughly and I set all the coefficients almost randomly without properly knowing the exact weight of each part of the body so to sum up it's important to remember that the rotation namely the speed of rotation strongly depends on the posee we take if the pose is sufficiently distant from the center of mass meaning our arms and legs are quite spread out then we'll rotate slowly as soon as we group and turn into let's say a ball then we'll rotate faster let's now consider the next topic the inertia of body parts I also call this through motion this theme is probably the most challenging for beginner animators while the previous two blocks are more or less understandable understanding inertia takes much more time but let's break it down with examples and you'll see that it's actually quite simple I'll start with a somewhat funny example I recently saw on the Internet it's about the behavior of our face muscles during a fall here we see the inertia I'm talking about the through motion what exactly is happening when falling our body our bones stop but the muscles continue moving because they had the same speed each part of the body has a certain speed and when the skeleton stops the muscles continue moving downwards the hair continues moving downwards it's important to understand that No Object will just abruptly stop it will try to continue its movement if it's not just a skeleton but a skeleton covered with muscles then these muscles will definitely try to continue their movement the same goes for clothing if you look at this collar the boy stopped moving but everything else continued moving downwards let's look at another example I prepared it's a jump with arms stretched out here we have a similar case I'm just trying to jump down and let my arms move further I tense the arms just a little not holding them in one pose too tightly then let them fall a bit and then I try to bring them back it works like this what does it show us it shows us that the character The Head and the arms try to continue the movement after the jump there was a certain falling speed and the head and the arms keep moving they continue their movement with this speed the point is that here the arm continues its movement if we look at its spacing we'll see that the arm doesn't stick in this point I also have another example here almost the same jump but here I deliberately let it freeze a little during the fall and we immediately see that something's not right there's some unnatural Movement we feel that something something's off here in reality beginners often do this they soften the moment of contact here the character freezes for a while and then continues the movement you should never do that it's very easy to check it in the graph editor you'll see that it's slowing down here this slowing down is unnecessary because when we look here everything seems natural there are no problems but when we look at this version we see that something's not right the arms look stuck they stopped at one point and the head doesn't go down at all only here and the pelvis got stuck here so it's very important to keep in mind this through motion just like in this video where characters where the guys jumped and their muscles continued their downward movement why does this wav likee movement happen here because the muscles went down during the fall stretched as much as they could and they tried to go back like a rubber band when you stretch a rubber band it also returns back the muscles move up then down then up again this is the body settling and as we see in the end it settled down there's some harmonic damping happening the same thing happens with the fall on the back when we fall on our back all the points simply try to continue the movement the arms try to continue the speed with which they were moving and the head when it goes down we see how it works it also achieves this through motion as I call it I made another version including common mistakes sometimes things like this happen first the character landed softly here as if on a magnetic cushion there's no stiffness here and for some reason it started slowing down along the Ty along the to I our objects shouldn't slow down here we see how it's lying down very very softly and it looks unnatural let's look at this example the hand here for some reason stopped in midair it didn't continue its through motion then the head did something strange there too I often see this that the character stopped like this and then the animator remembers that some bounces need to be added and they do it like this of course this is neither a physical nor a correct thing to do because each object has its mass an object cannot just flick like this making the same movements with the same amplitude in a short period of time the same goes for this arm instead of following this Arc this through motion it just goes in another Direction and does something strange there in theory this shouldn't happen again if we look at the original example here the arms started moving along the ark and kept following it without changing the arc it's important to understand understand this when the character Falls in a relaxed way they simply go down with this through movement I call it through motion for a reason it goes on by inertia if an object started moving in a certain direction its inertia will support its movement into that direction a human doesn't have too many inertia points so you don't have to worry too much about them however there can be more inertial points in the characters with various items like backpacks guns swords and so on in those cases yes there are points that need to be tracked that need to be thought of as inertial but again once you understand the basics of how it works it won't be a problem for you this inertia is the very thing that gives life to a character it indicates that they're real alive this again is the topic of physicality in my mind a character always consists of several key points that's what I realized during my time at Bonsai I started looking at characters differently if you haven't seen the video Everything is a bouncing ball I strongly recommend watching it it there's a shot from a cartoon showing you that everything is actually just bouncing balls we see that the feet pelvis hands shoulders head they're all essentially bouncing balls and in my mind when I think about animation I actually see exactly the same thing which makes animation very easy for me I always see the character in a similar way if go through everything we've seen before let's scale it down to make it a bit smaller this is the top of the head I don't track the head itself I track its top So eventually the character looks like this to me if you've seen motion capture sessions and seen the raw data you'd know that a character looks almost the same just with more points this is how I see the characters and I always keep track of them of these inertia points that's why animating is very easy for me I understand how it works I understand that they're all balls there's a reason why the very first assignment you get in school is bouncing balls because these bouncing balls they'll be everywhere later to me animation is what you're seeing right now when I animate I always keep track of these points doesn't matter if I do a handstand or I run or I stop it's always about bouncing balls for me and this actually is a very good approach I think as soon as an animator understands and visualizes it starts to see the animation as these simple shapes things immediately become easier if we look again at this jump it immediately becomes easier to understand how it works because you're not thinking about this you're not thinking about a large number of controls you're thinking only about the points that should move according to certain rules once you understand these rules animation won't be a problem anymore let's also look at the broken version you see there's this freeze that catches the eye this sudden slowing down the the same thing is here when we fall you can see how this ball changed its direction it just went along a different Arc for some reason let's look at the rotation everything is quite simple if you look at this one here I did the same thing to make it clearer for you this is how I work with animation well again in my mind of course I'm working with characters but in fact I perceive them like this of course I work with this kind of view but in my mind it's like this and when you see animation as bouncing balls it becomes much easier you have the main ball it's essentially the center it's the pelvis and the legs the feet at first when I worked at bansai I learned to work with the layer method I always started by working on the pelvis and legs then after I worked on that I moved on to the back and then to the arms and head this really helped me to understand animation better I just started to see it differently for me it was always something made up of certain components there's always the main component of course and it should be animated in the best way so whenever I started working I started with the pelvis and legs and after I did the blocking blocking plus I moved on to spline and started working diligently on the pelvis once the pelvis looked good to me once I believed that it could move that way I proceeded with working on the other parts of the body so I think this is one of the key moments in animation at least to me thanks to this I managed to achieve physicality in animation so once you understand it once you start imagining animation as balls it will become more of a technical thing since of course there are rules everywhere everything moves according to certain rules and the rest will be about your creativity what idea to choose how exactly the character will make certain movements so once you figure that out the rest will be just a matter of technique once you got the idea and you know your technical part you'll just need to create your animation and the last point for today is arcs this is the same point as in Disney's 12 principles everything moves according to its arcs and the same goes for the physical animation if you look at the current animation you'll see a lot of arcs here everything draws arcs all legs all arms draw some kind of arcs some circles for me probably one of the most obvious cases about arcs was in one of my freelance works let me show it to you I made a character with a lot of ribbons in all these cases I constantly created circles as you can see and the secret to all this beauty is arcs more precisely what kind of arcs we draw again Imagining the character made up of balls it immediately becomes easier it's easier to understand these circles these arcs undoubtedly in some parts this isight slly exaggerated for the beauty of the image and more often arcs are always refined if for example in your reference there is an arc that is not very beautiful not very smooth then undoubtedly in animation it will be adjusted and improved one of the examples will be acrobatics and gymnastics if you look at various gymnastic performances you'll notice plenty of arcs and a lot of these circles drawn by the different parts of athletes bodies so to sum up everything I told you today I'll draw a brief conclusion today I mainly considered physical animation the one closer to realism in many games physicality is neglected or it is exaggerated for greater stylization and that's fine too in stylized animation the contrast is even higher which makes the animation so attractive to the viewer's eye in realistic games there are plenty of cases where animation is being let's say pushed as well for example if you look at combat animations in many games you'd see that they're made quite sharp and impactful but if you'd seen The Originals the map for example showing the real lifelike motion you would be surprised at how slow and boring realism is in its true form but in some games this is presented as a special feature and that's fine too since these games are all about hyperrealism there the realism is exaggerated and you see that clean moap that all animators refine for many other games I believe that understanding of the basics of physical movement is very important because based on this understanding you can move into any direction you want you can choose the animation style like in Sony's Spider-Man cartoon where they break almost all the rules that I described today but again first you have to understand the laws of physics so you can break them in a smart way and create believable animations of course not everyone needs to know the laws of physics perfectly essentially everything I talked about today is about the center of mass and other things no one is talking about Newton's Laws although Newton laws are actually very necessary in animation so I wish you good luck in strengthening your animation basics as this foundation will help you to achieve a good understanding of movement overall [Music]