VR-Mess/research/sources/nimso-transcripts/rqLEL3kE4hc.txt

# How It Works 2 A - Half Life : Alyx - Hands & Physics (rqLEL3kE4hc, 1577s)

it's me name sony welcome back to vr today we are back in the uh in half-life alex and we're on the second episode of how it works uh in this video we won't be talking about movement anymore although there is certain things about it which is mantling uh that i could describe uh but what in what we're doing instead is talking about the hands systems uh the the way that the physics hands work and uh well the works the way that the hands work in general now i'm gonna start this uh start this a little dialogue going so that we can open that door very soon uh but the first thing i want to talk about is actually not the physics in itself but rather uh the hands there are actually three sets of hands in the game that might not make any sense but one of them is an inherent element to vr and the other two are necessary for the way this game handles its physics so what are these elements well the first one you can see uh directly in the menus this hand here what you're seeing is the tracking hand so these are actually perfectly following my real world hands and have no physics or anything like that they are never offset from my tracking that is the raw tracking that you're seeing in the menu and of course they somewhat match in game but in game we do have some physics hands that affect things as well that's not always the case however the things that are the main element are the tracking that we're talking about here so tracking always the same you have two of them and they're always there no matter what most of the time your teleport point comes from your tracking unless of course in some cases it actually goes towards the physics so you can see if i push my hand you can actually see the teleport line moving with my hand however if i if i if i pause the game you can see i'm actually pointing directly and my my other hand is actually sticking in to that hand so there we go you can push that and you can see that actually it's being pushed along right so that the teleport line is actually coming from the physics and which i will mention as the second one so the first set we've got is the pure tracking which you see here right the second set we've got is the physics hand now the physics hand actually collides with everything in the scene however the thing with the physics hand is it is always there and it's never actually connected to anything now that may not make sense but we'll get to that in a moment it's never physically connected to anything it is never stopped by anything other than the movement system and i'll explain that as well the third element is well the third set of hands is what you're seeing so the tracking you can see it here you can see it in the menu the the animated hands the actual visual hands you see them all the time of course because they move around and they connect to things and stuff like that and then the physics hand you can't really directly see it but in most cases the visual hand will try and follow it as well right so how does this all fit together well it depends on what you're doing so the game has a certain element to it which is that it tries to make your visuals look a little bit more natural in the game world as opposed to matching your tracking so the first thing it does is actually manipulate your hands uh depending on what you're doing so when your hands are neat near to something which you can see here it actually manipulates the animation but we're going to ignore the animation for now what it does as well is it actually moves the hand position what you're seeing though is not the physics hand being manipulated so here you can see i can push this hand but that's where it actually hits so you can see that the physics hand is actually offset here the animated hand the visual hand is separate to the physics and and you know what the easiest way to see that is with that teleport line like i said that teleport line is actually matching our physics right now so if i put my hand like this you can see how it offsets from that physics and the same thing applies in other situations as well like when you're moving towards an object like this so you can see i'll keep my hand straight like this and you can see it rotates towards that thing now there's a very slight blend so that it tries to match my tracking in reality what i'm doing is this but it's sort of mostly matching the actual point here before i grab it right and again you can see the physics is actually matching the tracking matching the teleport line there and you can see how the physics hand is separate completely separated from the visual hat so this is how we're handling uh the idea of what you're seeing and how it manipulates physics as well they are separated you don't directly attach your hands to the physics systems now me in my own work i actually have done that in my personal work my my visual hands are directly connected to the physics hands so whenever you see that the virtual hands the visual hands doing something the actual physics are doing that in my games that's not the case in pretty much every other build that you've seen now here the the thing i mentioned was that the physics doesn't actually connect to anything let's have a look at what's going on so here i mentioned that i can actually push on my hand here right and you can see from the teleport line that it is affected however i can teleport while holding something so let's hold something here and now let's look at where my teleport line is there's something weird going on that teleport line is obviously not matching what my visual hand is actually doing what it's actually doing is matching my physics hand so why exactly is my physics hand not here well this thing here is not physics and you can tell because if i push on it and you can see that i'm actually pushing on it right oh it's it tried to teleport me on top wonderful you can actually stand on the antenna wonderful anyways so point is if i hit it nothing happens it doesn't slide down it's only when you're grabbing it that it actually slides down that's not a joint that's not physics at all this is just a an animated motion that's that's how it works right and what actually happens is this physics hand you can see if i push on it you see how it's actually still there it's still there it's not stopped colliding with anything but this actual thing here has been grabbed by the visual hand the physics hand doesn't actually match it now you're probably thinking okay well this object is not physics so therefore that's why the physics hand is actually floating around what if you're holding a physics object well well well then something weird happens and then what we end up seeing in fact i'm going to use this this is very important right here because this i can hold with two hands then something really weird happens let me show you what happens i grab it with two hands and then look at my teleport line right you can see that my teleport line is actually not directly connected to this this object here however the thing with my teleport line is there's something really special about it it's still connected to my physics hand which is still physics as you can see it hits this wall and you can see that it actually rolls as well look at it roll look at it look at actually sliding and hitting things and you can see that directly when i actually try to hit something in fact let me just there we go give it a nice height position and you can see that you can see that here when i keep my teleport line active in fact i'm going to have to do it with something that's near a space when i keep my teleport line active you can see where my physics hand is and you can see how i'm able to manipulate this bottle while i'm holding this can while i'm holding the watering can if i don't have my my uh teleport line active it actually looks even cooler because what i'm actually doing then is this like magic i'm able to move the bottle without my hand that's because the physics hand is actually separate and never jointed to an object ever it's literally never jointed to anything right the physics hand is always active and it's where your teleport line actually comes out from so yeah you actually collide with walls to prevent your teleport line from being inside a wall right and coming out from inside a wall you actually collide with walls however it it's not what you're seeing right the collision is still active in all cases as well now that leads on to some other weird things because here like i said this is a physics object and this is not so what you can do is actually have both active at the same time let's try and do that ta-da so here now without my other hand look you can see i'm letting go and releasing it here i've got this slider active which is not a physics object so the physics joint that the game uses to create the physics object holding is still allowed to be independent this object however is stuck nicely onto on onto my my joint so i can still move this can but the slider the slider is also active at the same time here's the coolest part and this is what i was saying earlier where we've got actually three elements well here we've got four we've got this sliding one which is where my visual hand is entirely based on the slider and then we've got the can which is actually a separate physics object and then we've got our physics hand which is not colliding with the can but it collides with everything else let me show you grab so now i'm still grabbing this canister right this still i'm still grabbing this can with my other hand as you can see when i release it it's boxy back here because i'm holding it and with my teleport line you can still see that my other hand my physics hand is still there in fact if i hit it here you can see now that i'm holding this gun while my physics hand is actually being tracked by my visual hand now so here's the weird part now you can actually see my hand being pushed about so now if i grab this canister watch this you see how it hits into the wall and the canister is actually affected by my hand hitting a a a collider so the weirdest part about this game is that actually the the physics object is following not your tracking directly like your physics hand does so your physics hand is a physics object floating in air that follows your tracking which of course is this you can see in in in my in my space so you can see no no physics right but the can actually follows the physics hand which is incredibly awkward so what you have in in essence is we've got tracking that is followed by our physics hand that is then followed by the object we're holding so it always hits things when we actually try and move them it's really really unusual it's very cool but it's also very weird i've got something even cooler for you some things that you actually believe are physics objects or not at all so for example this door here yeah sure we can grab it and we can slide it and again of course our physics hand is still separate you can see me hitting it here right but that's not all this is actually not a physics object as you can see i can't actually push it my hand just goes right through but if i grab it very easily it slides that's all animated that's just a mechanic that's not a physics object now we've got something really special to talk about which is how then are we able because this is obviously matching my physics hand when i'm not holding something right so this is all just the physics hand how then is it able to move around so perfectly when i'm changing speed almost instantly right and that you can actually see very easily when you put your hand towards something so here if i move it and you can see again with my my my teleport line oh actually you can't because it's on the physics hand so when i'm moving my hand right so here for example here i'm my hands actually here right my real hand is over here right but here it actually gets stuck so i'm just going to keep my hands together so this is where both of my hands are right now you see right so obviously there there there's some natural physics to it and if my hand was behind here and then i tried to put it together here my hands you can hear the my controllers clipping together they are touching together but that hand can't get here because physics says no however how is it here then well what's happening is and this is really clear when you start doing something like this i'm gonna put my hand here watch what happens you see how the hand always stays in front of objects now this is actually much more easy to show when we've got some drawers and i'll probably show that in a bit as well but you can just show it here as well so if i just give it a crouch here you can see i can move around and obviously if i put my hand here it hits this object however if i put my hand underneath oh that doesn't work very well if i put my hand underneath you can see it goes on top right it's really weird what's happening is and this is something that was actually kind of mentioned by valve themselves in posts on twitter what was happening is we had a discussion about whether or not half-life would have arms and whether it should valve or someone at valve someone somewhere mentioned that actually what they're doing is they are doing some simulated arms personally i wouldn't call it simulated arms because in actuality what it is is a trace of the shape of your hand into where the hand is however where is that trace coming from it's not coming from anywhere along your body because none of that is actually calculated none of that is reliable information we only have tracking on the head and the hands what it's doing instead is tracing from the from the head outwards and hitting the wall and wherever it hits it positions the hand so you can see here in reality my hand just sort of rolls along the wall whereas if i'm in the movement system i can very easily smoothly rotate my hand right so what the game's actually doing when we move is it's not relying on physics instead what it's doing is positioning the hand directly it does that when you're moving without hitting an object and it does that when you're hitting an object as well it traces out if i can get the hand where you're where you're placing it it'll just place it there if not it'll place it at the closest point and then as soon as you stop moving it corrects it using actual physics because what it's doing is tracing that physics shape but stopping and it's positioning it directly there's no physics involved so how about what happens with physics objects then how's about physics objects how do they work then well physics objects don't do exactly the same thing you can see how they're kind of getting pushed about while the hand itself is doing that so here you can see how it jumps in but the can the can is not doing that the can is still getting pushed about by physics rotating and whatnot and sometimes getting pushed through through the wall that's because the can is just being repositioned to where my hand is it's it depends on of course whether the hand is being traced and hits a wall that's fine but the thing is that object still only goes based on where the hand is you see how the hand gets pushed back but the object doesn't it just moves to where the hand is being moved to so you're still getting that fake movement right you're still getting that fake movement but in order to keep the tracking from from going and you can see this if i kind of stepped to the right very quickly myself so here i'm keeping my hand completely still and you can see that in my tracking here right i'm keeping my hand rotated completely still i'm going to hold it with my other with my oh need a teleport there i'm going to hold my arm with my other hand nice and solid right so there we go i'm just moving with my whole body from left to right i should have had my camera on today but uh there we go right so you can see here that this can this this dustbin right gets wobbled about however when i do the same thing with fake locomotion nothing that's because there's no velocity there's no real physics going on but that leads to another problem how exactly does the game handle cans of objects so here we've got a complete store of objects which i just shattered most of them thanks to me pressing a button that i didn't expect to do right so now here we we have a bunch of things sitting on top of this how exactly i'm just going to do it like that there we go how exactly are they oh it's a one-handed object how exactly are they not being wobbled about as well look at this i'm shaking it quite wildly here in reality if i shook it you'd see them move so how exactly are they just staying completely still when i'm moving around like mad well what the game does is it actually has an intelligent zone and you can tell this because if i put objects on the other side stand still you can see that they just stay in place they don't actually follow the object that i'm holding as you can see you see how it just stays in place when i move that doesn't happen on the inside and you're probably thinking ah but hang on a minute so it has these connections that that prevent it from dropping okay well let's have a look in here then i'm gonna place it perfectly in the center there right in the center right so now i'm going to move oh other than this box here oh it's going to be difficult there we go place it right in the center and now you can see i'm able to move really quickly and the can doesn't move at all whereas in reality if i moved that thing would just wobble like mad right but of course the same thing on the other side yeah if i move like that it'll wobble right but if i did it without physics it just falls off because that doesn't have that special zone this leads to some real cool things which you probably you might have actually seen but i can guarantee you you haven't understood it right here's something really unusual and i'm just going to try and hold the problem with this chair is i can't hold it with one hand and i'll explain that in a moment as well but here you've got a chair now when you put an object on this chair for example this canister right ah damn i stand on the check for example this canister right it actually stays in position what that means is this area here is actually one of those zones a special zone that holds objects and that leads to something really cool because the game doesn't actually care how that object entered the zone it only does the stuff when you're moving when you're smooth locomoting right but it does it based on like what's in that zone so watch what happens here if i place objects in that zone they start getting moved look at that look at that like magic they start getting moved because the game has them in that zone now i haven't tried this myself but i'm really curious to see what happens if i place this can here and then put the chair so that there's an object in its zone and then teleport you can see there it is there it is i teleported with the can you see how that happens that's because the game knows that if you've got some object in your in another object and you teleport it has to move with that so what you end up with is this really really weird thing where you've got an object here and then as soon as you teleport you teleport with that object you could see the can was stuck inside the chair there really really cool stuff it's it's the most unusual thing you've ever seen but it makes sense once you understand why that's happening and um i don't know what um what what what i'm gonna do here because this video is probably gonna get a little bit longer than this i think i'm going to stop it here there is so much more to talk about when it comes to hands and physics one of those things is what i was complaining about just now which is this chair i can hold it with one with two hands but as soon as i try and hold it with one hand it just detaches right it just automatically detaches now we're going to talk about that as well but i think i should end this video here i left you with one unusual glitch or thing that i that you can do and you can try that anywhere so for example here if we get through this section here right skip this i don't care there we go you can try it here with this chair for example and this chair is really cool because i can actually hold it with one hand right so that's really cool what i can do here is place the chair oh in fact i'll place the chair like this because there's a zone on here as well you can move things around on the chair so if i was to take this object here and place it on there you can move around while it's on the chair which is really cool right but obviously that means that i can move things that are on the shelf just like magic i think i'm going to end the video here that's the end of this video thanks very much for watching if you're very curious as to what on earth is just go just you've just seen in this video watch it over again because it it is a little very it's very weird thing to try and get your head around how the game has to do certain things because it needs to allow for smooth loco and teleporting right and all the extra things that come as a result of that along with all the motion sickness things which is like digitalizing the movement so that you're not accelerating smoothly and then of course how the hand physics work to not show all that lag and you can really see that lag when you actually perform a crouch because with the crouch there's none of that clever stuff so that's what was happening here when you throw an object in here and you press the crouch button they get thrown about that's because there's none of that clever stuff none of the fakery going on when you press the fake crouch all it does is offset your real physical tracking right and you can see the hands get lugged behind and everything and even these weird these these information things like press and hold to toggle the menu they're actually sitting on the physics hand everything seems to be sitting on the physics hand with the exception of one thing the menu hands anyways i think i'm going to keep going too much on this video if i carry on so we're going to leave it here and there's going to be another part on how physics objects work when it comes to weight and and how the game balances all of that i am still working on the actual separate project so you will see a an attempted replication of some of this mechanical stuff uh in my own unity project as well until then thanks very much for watching uh any curiosities once again ask again in the comments and that's kind of the end of this video thanks very much for watching goodbye