Houdini Water sim basics 1

okay so hello my name is Billy Marshall and today we are going to be covering some fluid simulation Basics in Houdini at 17.5 so the two types are for particle Third's we are going to be covering today our foot fluids and we're going to be covering the flipped tank effect and the emits particle footage effect they can make particle fluids effects is going to include colliders and sort of interacting with objects and we'll show you how to solve each of the two and we may also move some objects through the flipped tank fluid and possibly at the end of the tutorial will cover some small basics on whitewater simulation but for now let's just get started on working with emit particles Lewin show me so first things first I'm just to make a ground plane this can be hidden later what we're going to have this was a base layer to work from so let me have sort of thing the water can initially collide with quick shortcut you can use to zoom on to your whole scene is if you press space and H at the same time you want to show everything in the scene from the default view this works on both Mac and PC as you see it operating on a PC but this is a universal shortcut so we've got our ground playing in the scene here here we're just going to name it floor just easy purposes don't they just see some import ground point so this brings up a DOP network so the DOP network is where all the simulations is going to happen so here we've got the ground plane one which is obviously you've seen and here we can change the grid size and the scale merge and go stacks over merge again and the gravity tool so the gobby tool is something we will be using that's due to the fluids and not effect we just have matter with this the flip fluids will all go into the dot Network so let's make we're going to start with the he met the particle third so this one so firstly we need an object to a net from so this example we're just gonna use a lot of box and we're just gonna put it above here so now just to show sort of the basic concept of what's going on so we're gonna rename this to emitter and if you press out on the keyboard it will lay out everything as it is yes I got a universal shortcut so I just put my geometry over there and it's on the tab so if you use this it makes groups we're gonna put this in the tab for colliders obviously not for Kleiner's and she changed to close out to like so once you've got your missus selected you want to click emits particle food and give Houdini a better time to calculate what's going on we don't want to it I met into anything right now which is another setting I'll go over a different day but for now just click enter that's all we want because it's going to collide at the ground phone anyway and now if you'll notice it's just changed camera also if you hit space age to change the camera that's the default I'll revert all the seconds of moving around in the viewport so back to basics so it makes it easier to move around zoom in and out and stuff so as we can see here it's taking us straight into our Dom Network we've got then two more sets of nodes for the fluid simulation so we've got the new particle fluid which is a useful node under the particle food interior which we will not be touching or messing around with so we can just put that over there we're gonna leave that enabled we'll just leave that alone so we disable the emitter if you turn off at the viewport it'll still be there when you just can't see it so for now which you can turn it back on and we're just gonna play and see what happens so so what I should just fall down and then collide with the growth plate which is exactly what's happening so obviously you can see on my screen it's starting to take a lot of time it's because just the amount of particles interact with an object is increasing so obviously there's a big splash on the ground thing so whenever we make changes make sure you go back to form on because if you have the slider on any other frame except for one any changes you make it's think up to simulate from frame onto that frame so you can load it so we're gonna move the emitter object to kinda leave to the center just because it's easier okay we go and again works the same as it did before move to the place you've got the particles coming out and then they obviously splash in it on the ground so once you swim all this out it's not gonna like a little little dots representing the particles like other stuff which we'll get onto but first let's talk about areas of the dot Network and what's actually important to control almost making this work so yeah you've got the sauce okay now the only interesting thing I like to play around with in the source tab is the activation so the activation controls basically if the source object is emitting so if it's set to one element so let's make a keyframe for it for example so all left mouse click will make a keyframe let's drag it to one as you see as I said it's got a cook from that so there you go by oh worth mouse click again and then change up to zero you notice it changes in the activation tab zero so I'll show you how it works so here we go it plays for a little bit drops like that he emits for a second and then completely stops so you've got a nice of splash possibly something like a quick bit of water from the tap or something like that so you turn it off and then does that so what's gonna delete the channels for that because we always wanted to emit to this let's just get rid of that let's cover the other important objects so at the merge is just merging in so he's got the activation thing in there which we have which we control in here so there's no worries about that let's change that one before I forget so we're going to flip through it object this is one of the two key parts of the water simulation so in here we have the particle separation tab now particle separation controls basically how many particles you have in the scene so more particles you have and more water that's going to be what in turn that's going to be the more sort of a simulation that needs to be done so as we can see we've got it to set to not point one which is just the basic if I said it's like north point no seven you know s now there's already a lot more particles and even compared to that so it's just really enough so if I play this out again there's gonna be a lot more particles interacting the scene it's gonna take a lot longer because there's how many more particles but I'll show you just how it looks so as you can see it's more detailed as more water it's more of a constant flow it's like bits and this is sort of something you want to try and achieve it looks a lot better you can just tell from the simulation itself spend a nice sort of clever ring going outside to be honest that looks nice we've not even done anything yet really all we've changed is the particle separation so first tutorial examples repel not pick not 9 just to I'm not gonna keep it on 7 just I'm not gonna get any smaller which you can that's just to sort of save a render time and improve the speed and quality of the video I don't have to keep pausing it stop so moving on you noticed I'm moving to the flips over the flip solver is the other key element of the water simulation that never use it so you want to go into the volume motion tab in here and go into collisions so what this is is the velocity scale is the key element you need here so a velocity scale basically means that it controls the amounts of you water reacts to things so like when we sort of drop down a splash before if I up the velocity scale the water will splash and react more so for example I set it to tap okay obviously this goes above 10 it's just showing the back of the slider but it goes don't you what you want the how you have this the better the effect is going to lock but it increases render time again but as you can see there's more reactions in the water making it look more realistic so one of the many balances you're going to need to get is the particle separation with the velocity scale obviously I'm not out here trying to make anything specific I'm just trying to show you how it looks with some colliding objects and sort of controlling how good the reaction of it looks so compared to last time as you can see there's a lot more essential like waves and stuff splashing from down it looks a lot nicer so I'm gonna say this made a rookie mistake like I said don't either stop it though if you don't want it to simulate something you can just hit escape and go back to frame 1 and then it can start simulating again so cool before we move on to anything else I'm gonna add a little Collider in and show you how to do that just so the water has something to connect with so as you can see I just spawned in another I'd another cube but I just hit enter once I click the object which will spawn it inside the world neutral so I'm just gonna make a bit of a rectangle here for the water to flow down and that's fine so we're gonna call that air collider exactly and then we're going to put in my collides top so to make this apply there you go into collisions make sure you've got that selected which we do you click stock object-- and I believe that's done so it's as simple as that to make a Collider now in theory the water should collide with this object when it's going down so you know it's the simulation is taking longer now because it already has something to collide with so I'm gonna pause that there's a few things I want to talk about here so as you know it is the object itself has got the war colliding with it but you can also see inside the object that water's going through so you're gonna think this is a problem because obviously if you're making a Collider you don't want the water just go straight through it so if you click into why can't you talk that way I can go onto your new Collider this is the one we want we're going to the collisions tab okay so firstly you want to whip up the wireframe of the objects okay so this is all the stuff in the object and then you want to change the division skies or division sighs sorry on the offset surface basically we want to control they were yet the sort of mold of the sort the bounding area of the box so that it's more precise so if we set this to not plane go back and then start messing with the surface I don't think we overly need to mess with the offset so if it's just because it's a basic EQ what decreasing the division size should make it so that there's more voxels for the water to react with so let's whip it back on smooth shaded go back to the object level and then hit play again I'm not see if the collisions work better so as you can see now now I've changed the voxel size there's no water colliding in the box sorry it's just because the boxes and voxel size wasn't detailed enough by the water went straight through it with more complicated objects as I mentioned the offset surface you'll be able to see here we go this is why we couldn't see it if you go back on to wireframe now and you turn the collision guide on do you notice how all of this area is now blue okay so before it was only set to naught point naught one gets a free month we start doing any changes do you see how less the detail is so that's supposed to be a rectangle object but that's how its internal collisions work so by decreasing this we make it more detailed and it looks how he's supposed to be so now everything will sit there and collide with the object just like I showed before so that's all good we've covered that we know how that works so now he started thinking okay well I've got the particle size I got a high one and I'm okay with the collisions and how it hooks I want it to actually like war so let's just turn the emitter off Charlie for now and this is where the particle foods tab come into play so here you have the display flag or thoughtfully set to do pinball but the real hero of this section is the particle fluid surface so that's our display flag for that and as you can notice now looks like a weird cube of water this is actually the surface texture of the water and how detailed is gonna look so a few things to cover here if you notice we also have a particle separation tab this is directly linked with the other one so you can control the particle separation from here but what you'd want to do is delete the channels from here so things could then change it but for now I'm not gonna do that because I think it's fine so if we go on to the voxel scale tab here will control how detailed the animation looks so obviously already know that we've been through that before it's the same thing again I believe if we go back over here remember we set our box or scale to oh never mind we're talking about a scale before so in the voxel scale is how detailed the animation is going to look so the lower the voxel scale is more detailed as well so it's not good five okay then we have the influence scale so this smooths out the water texture itself okay three is probably gonna make a water scale look a bit rugged so we're gonna set it to 5 we have to come to a sort of conclusion of how smooth you want the water because the smoothie that you have the water the more detail for what gets crowd because it's smoothing off the edges so for example I'm gonna leave it on three just to show you how it looks because we've got this place like checked here when I play it it's gonna take a lot longer but it's gonna flow look like water so I'm sure they pay out for you here you see it's a minion like was before I can offer goop right now but that's just because it's obviously rendering out but as you can see here splashing and this is what it looks like real water so there's a few sort of factors controlling this so obviously we've got the influence scale which is controlling the smoothing so I'm gonna do I said don't do but I'm gonna love this here and they still have to read cook it out but you see that how it's now a lot smoother no it does look like goop said it's for its kind of looking like water I think I might just keep it on three for this example and you notice the edges are a lot more rugged yeah maybe we will put it on see we're all sort of angle than such sharp and now it's not smoothed off so that's one so we've got a particle separation again which neutral and how much water has been spawned and the voxel scale so let's turn the voxel scale down give it a moment like I said this is calculators of the detail so you can't see it very well but that has changed detail and it will make the simulation go a bit slower but it looks more detail about so as you can see before with a lot faster because now it's more detailed it's taking all so I'm just gonna turn my voxel scale backed it off with seven just so I could show you how the animation looks our trusty escape key I think to stop this from Samir there you go don't worry when it does this it's just because you've cancelled the simulation at that point y'all saw it's a smart player again a bit more cash for the sim we'll get it so it's works before but you notice how it's now a lot faster the balance is controlling the voxel scale and influence scale in this part because you want it to look smooth and detailed but you also don't want to take absolutely ages so you're gonna find the key to your project that you think he's nice and white well so right now like I said you're not exactly a big goopy water well that's just because as you basically think of this is like playing a tap on a spoon if you check this a plays the back in real time so I'll play these 37 frames in real times about second of animation I think it's being a bit slow because of the sort of caching and the simulation itself at least it's not absolutely wrapped in it well there you go we've got no splash animation colliding with an object so I feel I think before we talk about the other sections once you're all happy with your how your animation looks with the collided with an object sort of thing you have two caches here now once every is happy with everything you're gonna want to cache these out so make sure you have this file extension so we're gonna kind X that find somewhere you want to say that blah blah blah I'm not just gonna cash it out but you will lead to fights when you were saying it give it a name put this fire extension on it and then save to disk now this will make file cache where it'll render out each individual frame it's the actual sort of height geometry so you can notice on blocks so you want that to be run down by the cache once you've done that you can then click load from disk and it will no longer the cash on the system and won't take nearly as long so once you got all your animations perfect and spot-on you're on a cache then you want to do the same thing for surface cache which is how it actually looks so make another folder where you'll be the first one give it a different name make sure you have a file extension on save to disk once sold on load from desk and the animation should be smooth and from the blog because you've already got it all saved out I'm actually check the load from disk it'll load it from your save file I don't have to keep simulating you out so it'll run smoother than you see so now this is the basics of basically fluid simulation I'm gonna talk to you now about applying them to the to the flip tank object both sort of working a similar way well I'll be back in a second to discuss that

Channel: C00PLY

Views: 1,583

Rating: 5 out of 5

Keywords:

Id: w81-QTTL7jY

Length: 21min 30sec (1290 seconds)

Published: Mon Nov 25 2019