Tutorial: Crown Splash From Scratch

hello everyone in this tutorial i'm going to show you how you can create a ground splash from scratch covered surface tension and small scale fluids quite a bit in the past but i still think this is a useful practical example it's been requested by one of my long-term patrons jackson okoro uh he's pretty good with flip flops himself likes to do some really cool small scale setups and what i'll do in this tutorial is set up a ground splash from scratch and after that i'll have a quick look at the shelf tool version so you can see the differences and the similarities and how both setups try and achieve the same thing and hopefully that will give you a better understanding and make it easier to get the look you want from your shots okay i've started up a clean beanie session and i browse to the potting fluids tab and to get us started i'm going to create a flip tag and this is just going to be our starting point 5x5 is a good size for testing i'm not going to be worried about a real world scale and going microscopic the sizes when you get to these sort of small scale sizes you're never going to work at physically accurate scales anyway because it's just going to be too small in hoodie units and in real life it's usually something we see through slower cameras and not something we look at every day there's a certain amount of trickery we can get away with for our splash i want to create a fairly shallow tank so i'm going to pull this up maybe give us a little bit more height something like that and the reason for the shadow tank is so that we can create a big splash but not have as much of a recoil and a secondary splatch afterwards and it's a little bit less fluid so it might be a bit faster to swim as well and you can play with the depth of the tank to get different looks okay next up we're going to need an emitter as well and i'm just going to rearrange this stuff a bit i'm not going to worry about a fluid interior at the moment so we can get rid of that that's our initial flip tank and they have a sphere and this is going to be our droplet i can reduce its size maybe a little bit smaller something like that and with the size of this droplet it's definitely going to hit the splash is definitely going to hit the sides of the tank but for testing we can keep the tank small and then enlarge it once we're happy with the results so i'm just dropping a transform so i can move this up a bit maybe around there so we give ourselves a little bit of headroom and we can convert the sphere to a couple polygons subdivisions and i'm just going to use the shelf tool again to create an emitter from it and it wants me to select the flip tank i can do that and just hit enter and it's actually created a second flip sort for us which is not what we wanted but let's just leave these and keep the imager i was surprised i didn't expect it to do that i was airing out because it's probably referencing something in the other one or maybe it just needs to rebook no it is complaining about something ah and it's an error in the sphere all these references are now broken i just need to re-link these i think i'll probably just pause the video and fix these okay that was a bit painful but all the links are fixed now okay and and on the emitter while we're here i'm gonna turn off the thickness because i just want to turn it from the sphere i don't want it to be bigger than that the rest is fine we can leave it like it is and then i need to do some cleanup work here as well because it's created more nodes which we don't want i can't delete that and i can delete that here call this droplet now we put our initial flat tank and our droplets and we can hide that one and i'll dive into the other dot network okay oh i'm gonna remove the merge because not need that then on the flip tank i think we can probably get away with a bit more resolution to start with set this point five then i'm going to set the grid scale lower to 1.5 instead of two so that just means we have a few more voxels compared to particles and that's good for surface tension you'll see it's the recommended amount as well because you want some higher resolution voxels to work out the curvature because that's what surface tension is is based on it's a volume based force so it's calculating the curvature of the surface volume to apply the force but this is a practical example so i'm not going to get too technical on our objects these are set up there's nothing else i want to change there i'm using narrowband at the moment i can probably simplify it and turn it off but i'll i'll leave it on for now on the philips solder i'm going to change it to the swirly kernel and this is generally better for small scale fluids because uh just source velocity transfer but more accurately and you get a smoother smoother fluid i'll leave everything in the solver bounds are linked to the sub level one and i'll leave everything as else for a default now i'm not gonna turn on surface tension yet the first thing i want to do is just make a splash so the source i only want to sort for one frame so i'll say if dollar ff equals two equals to one actually let's make a dollar sf or if we decide to change our start of our simulation and i'm just going to hit play to see if this works and you can see we get a droplet dropping down and splashing into our liquid and we can see the splash isn't very big but it's definitely working so that's good so i'm going to go back up and in my initial i'm going to make it even thinner the layer of liquid and then for my droplet i'm going to give it some initial velocity and i can make their initial velocity fairly strong like -12 so it's shooting down faster than gravity so to get a nice big impact so you get a nice splash then i'll jump over to the autoduck network on the particles i just want to set this offset scale to zero because i don't want to interpolate the problem velocities because it's not like i'm making a stream i just want to get the droplet out and i'm going to shoot it out fast let's see players you would get now okay we get a little bigger splash now you'll notice as well the recoil is actually hitting the top and splashing down pretty fast that's simulating very quickly i'm just going to lower the resolution a little bit more to squeeze out a few more particles and then i want the splash to be even a little bit bigger for -14 so all i'm trying to do is make a big splash as quickly as i can and get a general size i like before adding surface tension so this is looking okay another thing worth testing is you'll notice if we if i just double my sub steps that drops coming down really quickly so it's not resolving the splash that well you can see as soon as i do that i get a bigger splash so the reason that's happening is that impact is just being solved a lot more accurately okay i'm going to stop that after a couple of frames see what that looks like that's a nice big splash now it's time to turn on some surface tension so set the sub steps back and maybe we can make it one and two for now i'll go over to the volume motion tab go to surface tension turn that on and we can start with a low value something like two and then if we go to the particle motion tab i want to change some of the reseeding settings because it's surface based i want to over sample a bit so i'm going to over sample the surface by two and i'll add that bandwidth to 1.5 what that means is our reseeding is just gonna source a higher amount of particles per voxel around the surface of the object giving us a more accurate surface which in turn is going to give us more accurate surface tension results so let's simulate this and see what happens i'm just going to create a camera as well so we have some sort of a consistent view as well so i realize that could be useful for us to compare with if we need to maybe something like that uh now let's see what happens okay you can see we're not getting much of a result not use my timeline for now it's looking pretty similar to before we had the surface tension and that's because everything's happening really quickly if we try and pump up surface tension force you will see it's going to start breaking and it might might have a good result initially so i'm going to sum that and let's see what happens at 10 but once this gets too strong you might need a way to slow the sun down and that's either going to be through sub steps or reducing all our forces okay we can see it's doing something but not really what we want so let's see what happens if i keep this value fairly strong i might wanna just boost that downward force even a little bit more go up to 16 and then in my flip solver i'm going to set the slot to time scale to 0.1 that's going to have the effect of everything moving 10 times slower what that means is we will need more frames to simulate all of this so now if i hit play to cook the simulation you can see the droplets falling down a lot slower but if we look at say the velocity you can see the velocity is still really high because it's all showing us the real time velocity so it's a similar sort of idea as setting the gravity to 0.98 instead of 9.8 and you can see now hitting the side a bit quickly maybe i've gone a bit big on the splash but as this is developing slower we're starting to see a rim forming and we see some more of the telltale crown splashy type shapes forming in there so what i'll do is i'll i'll lower that back down go back to 14 right where go to our initial tank and make it a bit bigger eight by eight so we have some more space in there for this to develop and i'm going to keep that surface tension at 10. maybe give us even a little bit more resolution it's running very quick on my machine and it's still it's not even a million particles let's be crazy and make it 2.5 and let's cook this and see what results we get okay the simulations run for just over 50 frames now you can see that now it's starting to really work and we're getting some nice big droplets forming and it's starting to look like a crown splash so i'm just going to go to the end here and we can see we're running in a tank space again so if if this is too much surface tension for you then at this point you can reduce the amount of surface tension if you want the effect of surface tension to be stronger then increase the surface tension amount you'll get bigger droplets and you'll get the surface sticking together more so it could affect the size of your splash a little as well depending on how extreme there you go but yeah this is we've already have a working setup and this hasn't even cooked for 10 minutes yet okay but i'm going to stop this one here let's tweak the settings one more time so what i'm going to do is just one you can double our surface tension and left the substeps to one and two which is which is okay um i can reduce the the time scale more but i'm going to increase my substance a little just to make sure that it's accurate i'll make it two and four i'm trying to keep it as low as possible but also get some nice surface tension and i just doubled the surface tension but i don't want to reduce the time scale even more but i'm trying to get some nice results okay i think that that should do it and i'm going to cash this out let's just set that up get my custom file cache i'll extract the mesh now move that out of the way and i'll just call this ransom and i'll set it to read from disk and i can run out 240 frames and before i get i'm just going to make the tank a bit bigger again 12 by 12. and then i'll write out 240 frames and i can write that out in the background so i'm just going to save the file and then hit save to disk and background and while that's going we can have a quick look at what you get from the shelf tool okay i've opened up another instance of houdini and i'm just going to go to particle fluids and create brown splash from the shelf tool and hit enter and let's see what we get so again you'll see that tank made pretty shallow and we can ignore this that's our emitter that's our initial tag the second dot here which shouldn't be there this looks like a bug let's get rid of that i can hide that our emitter so on this one we've got a force of minus four and the velocity and if we go to branch flash them you'll see our emitter is coming in it's only saving for the first frame but what's being done differently on this one is the time scale is left at 1 but the velocity of gravity is being set down to 0.01 so essentially side effects is doing the same thing they're actually reducing the time scale by a hundred so you multiply that by a hundred you will get normal gravity like that and then because they're slowing everything down by 100 this is where they're making it slow motion and you can go over and you can see also added a bit of over sampling to reseeding and on the surface tension itself it's got a lower value than mine but then we also have to remember all the amber forces are lower as well so i'm only slowing things down by a 10. this is going all the way to 100 and it's reducing all the forces instead of reducing time scale but essentially it's the same goal it's having the fluid move slowly and everything develops slowly to give the surface tension a chance to evolve and give you those nice droplet shapes a force like surface tension tends to need a lot of substeps or a lot of time to to evolve it's kind of the same thing with sbh based liquids as well in that case you tend to just have a lot of sub steps and if you want to speed this up afterwards there's always stuff like time ramps with the retime node and you can check out one of my other tutorials i've got a tutorial about retiming flip using the retime okay once we've got some frames to look at i'll jump back over to my cross splash and we can see what that looks like okay so that simulation has now finished and then actually ended up running four of them the first one didn't finish all the way through but i figured let me make four different versions so that we have a few different ones and we can compare settings so this is the one i showed before with surface tension of 20 and the down fourth of 16 with the new sub steps and you can see it's pretty strong but we can even at this resolution which we can probably push a little bit higher for something final and we can so we can see that there's some really nice shapes happening um but because the strong surface tension is sticking together quite a lot so i made a second version and for the second version i reduced the surface tension to 12 and everything else stayed the same and it took just under 24 minutes to finish and let's play this one you can see with less surface tension we get a bigger splash but if we give it time to develop we still get some tendrils coming off and some droppers forming in our crown and this one's a pretty nice one as well and let's jump to version three so for version three i decided to increase the surface tension again but make the downforce a bit stronger so i increased that to -18 so it hits the surface a little bit harder but the surface tension keeps it the fluid together a bit more and that that was a bit slower it took 26 minutes and that's what this one looks like and you can see we get an even bigger splash because of because of the more aggressive force but we get some more droplets detaching and our simulation actually gets a bit too big for our tank probably need to increase the size of our tank if we want to use this one but it's looking pretty cool i think next up we've got a last one where i bumped up the surface tension even more but i reduced the downforce again to just 16. but just just subtly nudging values around seeing what different results i get so yeah we can see with this one so this is close to the the first one settings just a bit less surface tension and we start getting droplets detaching this one this one and the first one probably looked the most macro all obviously all of them are but if you can't imagine what scale this would be my favorite is probably the third one even though we need more space for it let's go to number four since we've got a whole splash of drop coming off there and let's see so that's frame 330 i'll say 230. um i'm not really going to cover meshing in this one i'll i'll just show some quick rough mesh settings that we can have a look at but i think it might be better to make it separate a video about meshing fluids but later on but yeah as you can see from this like once you've got got a setup to control your splash you can start playing with different values so and the values you can play with is strength of surface tension how hard the droplet hits the fluid surface and then you can also adjust your substeps which is going to affect the look a little bit of the surface tension and also the other thing you can do is decrease or increase the size of a drop hitting the water that's the one thing we didn't test but if we look at this one we like if the droplet's a little bit smaller we'll get a smaller splash as well so you can do that instead of increasing the size of the tank that covers everything for the surface tension we are on version 4 which is the last one i'll go to frame 3 or 2 30. we have some nice shapes and i was just using the surface tension i got surface tension on my brain now i was just using the particle fluid surface to visualize i'll turn off the velocity visualization and set this to polygons i might already have some settings turned on i'm just going to give that a little bit of time to cook okay so there you can see we can get a fairly decent mesh what i've done i've reduced the voxel size just a little bit and i've gone for some fairly basic settings turn the die light and rode on to keep some of the detail and i've got a means moving between the two so i flip these around let's just because the means move after was just a bit too aggressive and then i've got this curvature flow smooth just one part of it i think the mesh is not perfect but it's not too bad we get the fluid building up on the edge like we want sometimes droplets coming off and if we want more stuff coming off we just hit the fluid hardware and because the tank is very flat we do get hole at the bottom so depending on your camera angle this might be a problem the two solutions for that would be a deeper tank and what you can do as well is add some extra bdb at the bottom try and fold that hole to try and cheat it that way but as soon as you drop the angle somewhere like this it's not really a problem okay so that's integrating crown splash from scratch i hope this walkthrough makes your life easier next time you're creating a splash this hopefully gives you a better understanding of what settings to change and how to change them to get your desired look thanks for watching bye if you want to see more videos like this or if you just want to support me go check out my patreon page or follow me on vimeo or youtube and if you like this video give it a like and as always to all my patrons thank you very much for your continued support i can't do this about you guys

Channel: Zybrand Jacobs

Views: 789

Keywords: tutorial, houdini, simualtion, FLIP, surface tension, macro

Id: _UaWj8AxRIk

Length: 30min 15sec (1815 seconds)

Published: Tue Oct 26 2021