Water from Houdini to Maya tutorial

all right everyone this is my Houdini tamiya tutorial we're going to be working with the flip fluid simulator in bikini and we're going to surface it and throw it into Maya this here is just a quick little scene for little balls animating and our goal is to have a splash effect from this tub onto these balls yeah so start I animated this I mean as balls beforehand what we have to do is we have to export this geometry so what we have to do okay so we don't to export our entire scene here so what we're gonna do is we're in an export selection and select the FBX the reason we do FBX is so that we we can keep our animation geometry with us if we don't then after you do any 1500 BJ or Maya file it won't bring into Guinea with the animations save this so we're done with Maya for the most part so in Houdini we got to import our geo by import home box the X select our file and we can leave all the stuff you don't have that extra Lumbo click import and we have our geometry as you can see this here we do not have our subdivisions since my exported them since in Maya we have smooth preview it didn't actually export the smooth preview so we're gonna have to do here is select our geometry separate them and subdivide them so that we can have proper collision geometry so if you press tab type in Geo we've got a geometry node grab that let's rename that to flip underscore geo and in here we have to reference our FTX geometry so grabbing an object merge we can select object one and select our geometry our cylinder so as you can see it doesn't grab the geometry exactly we need we have to do is select transform into this object and we get the geometry you want so we have to do is now subdivide sub divided by three minus three three view is a subdivision of three you see that and that looks perfectly fine now we can grab an OL patch that to that and let's label something nice out out tug and that's cool so we got to do that for the rest of the pieces here we can do it you can select all three these nodes just like be selected and select our new geometry let's select our ground plane and rename this out G playing okay do that for the rest of the spheres grab this copy paste that excuse and if we rename this to out sphere one we da understands numbers and strings so we're to just pasted automatically rename the null g two three and four so you got to go back to the object merchant some locating it we can just type in sphere to spear three and sphere fork so if we look here we have all our bar geometry imported and subdivided so we got our collision geometry nice and dandy we have to actually make our fluid geometry so how we could do this is we could actually have a ball collide into the tub and splash out and make contact with our ground plane in these four balls but how we were going to orient our camera we won't actually be seeing the tub so we can cheat our way around it and emit outside of the tub what we're gonna do is make a plane or a grid and we're going to move it outside frame and we're gonna make a particle system you make particles into our scene and collide that way we much more control than allowing physics and having to fine-tune it finesse our physics with the slit the splash from the tub and it'll just be much easier to control so we'll scale this down make it a little wider in its position we look back on our camera get out frame move it off a little bit out and rotate okay cool let's write a null for this so can be referenced later let's make this out mitr cool so we have everything set up for this now all we have to do is actually build the simulation so we will tab top net for Network and inside in order to make a fluid simulation what we'll need our particles and the particle object so we will grab a flip solver and you can see that it's asking for the source of our particles and the actual fluid to solve so we'll grab a flip object or a physical thing to solve and the particle source for the particle source you can use a standard pop source much simple or very simple super easy to use pop source bring that in and connect that to our source so we in order for the pop source to actually emits particles we have to choose where to embed particles from and that's we're going to use a stop and if we look here we can see we have our emitters nulls always default to the top of the hierarchy so super easy to find and so now we got two things meeting particles the original pop up flip object and the pop source we're gonna get rid of the pop object so now we just have our particles emitting so for the press play we can see that a particles are emitting but they're not moving anywhere that's because we need to give it its initial values of velocity so first to make things a little bit easier to see we can go to our flip object and go to guides particles and visualization you can make them particles instead of giant spheres so if we look at them they're much easier to see much nicer to see so you go to pop stores attributes and we can have it set to its initial to an air inherit velocity from the top itself but we didn't give it any velocity attributes so we're going to set initial velocity salt click play you can see that the kind of moving well that's because they have velocity is zero but it's got a random inherence of a variance so we can make the velocity negative 1 to 1 we don't really know it's randomized so we don't want to randomize we want to tell where to go so we said all these that commute to zero and we have - reset the sim and we want it to go into the x-axis but in the negative so we're gonna grab velocity of let's say negative 10 let's rewind you press play when you see our particles are moving in the negative direction at 10 units per second on the x-axis oh that doesn't look too cool that doesn't look too realistic so what we want is a splash to be parabolic so what we're gonna do is we can give it some gravity force so we tab gravity and our only option is gravity force we hook that together weari sim and then moves add the downward slope that we want the parabolic slope we want with the negative 10 but it's obviously not connected so what we're gonna have to do is we're gonna have to give it a little bit of velocity maybe a velocity of 6 initially so what's gonna happen is it's going to move to the left 10 units per second and up at 6 units per second but with gravity affecting it slowly pulls it down so those particles look like they're gonna connect with these spheres which is cool this splash doesn't last forever and obviously only has a certain amount of water it's gonna splash so we can tell it when to emit particles and what not to which is by this constant activation so we can tell it to emit from frame 1 to frame 12 yeah 14 that sounds about good so if you alt-tab any of these black boxes in Houdini it keyframes it so we're gonna tell it is that on frame 1 to frame 14 it's going to emit particles 1 means that emits a zero means a dozen so if we go through 14 and then frame 15 it's going to have a mission value of zero play you can see that in you may particles and then at 15 it cuts off no more particles getting emitted which is about right cool so all that's left really is to make the interactions with the ground plane and these four spheres so in order to add collision geometry we have to add to our treat so we grab emerge grab that into our tree and we need to make static objects static objects basically equation objects because things don't have to be static so in our static object you can go to the stop app and we want to choose the stops that we made before for the Noles so sphere one and then if you alt click drag from a node you can duplicate the mr. Greasley and we're going to do is we're going to merge all these static objects together with one two three and four for each of the spheres sphere to sphere three and sphere board cool and lastly the ground plane so I'll drag one more and get the ground plane now if we're to play you can see that oh my god we need to do is it doesn't move the ball so move that's because we have to deform with the user deforming geometry which is the geometry that is moving so now we're to press play it is affecting the the animation so to understand how this fluid system is working is that all these white particles are particles are moving at high velocity while these light blue particles are moving at a little bit slower velocity so the more the faster the particles are moving the more blue they're going to get to the point where they're white and things are slower or I'm gonna be a little more blue and we can tell that these particles are colliding with the sphere because they are turning light blue I means there gets some kind of resistance um okay so if we were to look at this a full speed they do make contact and they do hit with the floor but the thing is is that they're sliding forever they have no friction on the water so we can incorporate some friction by going to our flip object going to physical and you can see that there's zero friction whatsoever so you can do is you can drag that all the way to one that way it's going to collide with the floor and stick to the floor so we're gonna let that same out okay so these particles are moving a little bit after the UH after they make contact before we can probably just bump up the friction decrease the bounce increase the bounce forward and we can bump up the friction to something like that okay so the sim sindh out and we can see that fluid comes in collides and cried to the floor the particles do slide a little bit well that's just because that's how fluids work they roll on top of each other so these particles only are interacting with the floor and not the surface so as soon as they stop and roll off the particles on top of and may contact the floor that you stop moving okay so this looks super cool II I'm satisfied at this so we can pull out and all we need to do is save this and need all we need to do is make a geo node we're gonna save this out as a surface and then we can bring it into Maya so we're gonna label this clip import sorry importing our flip fluid and we need to reference the simulation that we did from the previous node and we're gonna do that with the top IO there's two things we need to input here and that is the top Network in the Dom node so the network we did well this table net and the top node is the node that is the actual foot itself which is this flip object so we go flip top node and we just look for our flip object one cool we see like the background we see the sexual stuff here that we don't want to see so all we got to do is hide all of these into here and we got nothing that's because we have to tell it what to reference so we go here to our fields okay plus and when there's nothing here it basically means everything's there so it's saying well what object are we looking at everything all right what field are we looking at in flip object one everything so our geometries here Sofer to play this back all our geometries they're our colliders aren't there but that's because we want to surface the fluids and hot close surface so we go back and it's only playing really smoothly because we have a cached if I were to change something I would have to recast it so what I'm gonna do is I'm gonna do a quick little file cache and that's gonna save out our simulation so if we were to close this program and bring it back up we'll have our stuff running smoothly still so file cache we want to save our file we're gonna do is we're gonna copy this because that's gonna be the name of our file a dollar sign hit name is the name which is untitled cuz I didn't save this and the OS is gonna be the file cache one because that's the name of the node the dollar sign F is the frame number and BG e ofc is saying basically that this is a simulation so we're going here we're gonna I'm just gonna see about my desktop I'm gonna make a new folder name a cache and see it out accept cool um and I'm only gonna save this to frame 74 so I'm just gonna go here and label it 74 but it's not gonna work because it's actually saying the end of the frame of the last frame which is 240 so we're going to do is right-click delete channel and tell it that not to make it the end of the frame so put our own number 74 and save the disk okay since it's already cashed out it took no time to save so we're gonna cook loaded from disk and now no matter what we do you can close out of the program it'll still run just as smooth cool alright so now the last step is surfacing and exporting so we're gonna do here is we're going to type surface for particle fluid surface grab that and connect it and you see here's the surface polygon suit what it's gonna do is gonna take all our particles and calculate that into a mesh so if we're to go to frame 20 we have our particle fluid so it kind of looks weird it's not exactly what we want and that's because we have to actually finesse our particles from the simulation the particles are super far apart and how it calculates is it takes the distance from there's a particle here a particle here particle here apart over here that's my guesstimate but it's property accurate and it says if each particle has a radius of 0.0 0.7 5 then it's going to mesh the two particles together if they're a little bit far out it's gonna make its own particle and that's not what we want we kind of wanted a little more dense so we're gonna go back to our object level go into our import and we're gonna do is we're going to increase the amount of particles emitted go to source our sorry booth and we're going to increase the the break and what they are - something like 550 thousand it's gonna have to re cache we go back here and we press play and it's gonna take a little bit longer to sim than before and that's because there's no simply more particles just ten times the amount of particles okay that should be long enough looks cool you get a lot more detail in our particles it looks a lot more than s before reading it to see these the particles behind the spheres because obviously they didn't get past so cool we look back in let's see it's surfaced let's show and it doesn't change and that is because like the file cache as I said before no matter what happens we see the same particles that we saved that so we're gonna do is we're going to save the the simulation we just made so we're gonna we can either overwrite or we can just make a new file and we're simply going to make a new file by labeling this one V 2 and now we click Save the disk and we already cached up to frame 42 so it went straight to 42 and it's gonna cash out the rest so give up that few seconds and it should be done cool our particles are done caching when we save them out and great press play super cool all right well let's check back to our surfacing let's go to frame 24 see what that looks like looks a lot more detail um let's get a frame where it collides with spheres see how that was cool that's a lot of detail it can be a lot more finessed but that's at your own risk it's gonna take a lot more weird actually look at the file size desktop desktop cache right not a quarter of a gigabyte um I've easily ramped up to like 10 gigs for a flu simulation it does get a lot beefier it gets a lot thicker yes as you put more particles in but this is fine I guess for a time being so we got what we want looks really cool if we were to render this let's just know I'm gonna have to worry about rendering now I guess so we can just take this model or this geometry we have here and import it right into Maya so how we're gonna do that is we're just going to add so normally you take something as an FBX and export as an FBX but the thing is is that this is such dense geometry and it's not saving it as an animation but it's saving it as a new model every frame because that's basically what it is it's remesh in every frame so we're gonna do is we're going to make an olympic file an ABC file so we are going to whoops we're gonna go to our export tab we're gonna Rob basically means output like export so we're going to do a wrap Olympic we're going to tell it to render a frame range and we're gonna again go back to delete channels so we can import our own number 74 and tell it where to save to you is gonna see if it as one file so it's not going to save it as like a sequence like our cache so we can just put down a desktop and name this our Flip export clip export make sure you label it an EVC at the end it doesn't automatically put in the extension for you so all these don't really mean anything to us we don't need this so you just click render to disk let that save and you should be able to import it tomorrow cool alright stop consuming you can go back to our mind file and back to our original scene and all we got to do is go to the animation tab cache Alembic cache and import our Olympic file so just locate our stuff bring it in give it a little time you press play and here's our stuff it's kind of clunky and our viewport but I can assure you everything's there so let's get this cool that's a feature exactly the frame we had in Houdini yeah so that's basically our flu simulation looks cool looks real look sick you can do everything you normally do in Maya so you can give it its own shader you can give it an Arnold shader um I don't recommend doing an Arnold shader for fluid because simply put it Maya isn't that good when it comes to fluids that's why I don't prefer doing fluids in here but if you need to you can do something something cool you can give it a little transmission with high specular give it something nice and uh yeah that's how you import your fluids into Maya

Channel: Janks

Views: 8,731

Keywords: Houdini, Maya, Fluid, Water, Sim, Simulation

Id: T1wnXA80aGw

Length: 24min 53sec (1493 seconds)

Published: Wed Mar 06 2019