Houdini In Five Minutes 10: Procedural Animations Using The SOP Solver

let's have a look at a few of the unique strengths of Houdini in building this type of setup this organic thingy growing the principle behind it is copying geometry onto itself over and over again let me show you what I mean by in the obj context dropping down a geo node diving in there and dropping down a sphere which we will set to be a polygon with a rather low frequency of 2 and the procedure I want to do over and over again is just scatter a few points on it maybe not so many but say 24 then use those two copies spheres onto those individual points so again drop down a sphere which was said to be a polygon as well with a lot of frequency of 2m let's scale it down to say 0.1 which we're going to wire in here so we got this and as we've seen in a previous tutorial to repeat this operation over and over again we could for example use a for loop however in this case I want to make an animation out of this and want those fears to appear successively over time and yes you could animate a for loops number of iterations however that would get pretty slow because for each new frame the for loop would run its full iterations while it just needs one additional iteration and in Houdini's geometry level in shops there is a concept and a tool called the solver which is doing exactly that operating on previous frames geometry so let's drop that down the solver here we've gone wire in our sphere in the first slot here and let's just copy these three nodes here dive into the solver and you will see this there was five slots you get direct links to your four inputs that you had on the solver node so our geometry would come in here plus you're getting an additional node called previous frame which enables you to access the geometry that we had on the previous frame in Houdini and that's what we're gonna use in this case and to employ a proper technique the first thing you want to do is drop down a switch and a switch just switches between its inputs that you wire in here depending on a condition here so when I have at this select input 0 it selects this node as an impotent one selects input 1 and as we're on this first frame and we do not have any previous frame on the first frame we need to select input 1 which we're going to do with a short expression so we'll check if our frame equals to 1 and if it does so this expression outputs 1 and thus - this here and then on the second frame and switches to the previous frame and keeps it there for the rest of the simulation okay let's paste our three notes that we copied and wire the switch into the scatter like so so when we go up one level and toggle real-time and hit play you see this happening this kind of moving spheres here and that is because on the first frame we copied those fears onto our initial first sphere and then we are using this geometry here to scatter a few other points so they over time move outward a bit because all those points will be scattered on the geometry that's been there in the previous frame which for example in frame 22 of the next frame the points would be scattered onto this geometry what if we don't like this kind of moving thing and we'd like to keep the previous geometry from the previous frame and add this to it well let's head into the solver and drop down a merge so we're gonna merge the geometry we're creating with the one that's coming in to our solver from a previous frame Y with a switch and then highlight this here as our output again go up one level make sure the solver is highlighted real time toggle is checked and hit play and now you can see this growing motion here that's already looking pretty neat one thing I would like to change however is to go back into the solver and for each solver iteration so each frame I want to change the seat that's in the scatter node here so the global seat here and to change this seat per frame I'm just gonna drop out an expression dollar FF for the frame number of the current frame number so the c2 changes for the run of the simulation again go up one level hit play okay not too much difference but we're getting there and we could perfectly leave it at that if we like this kind of spherical look here however to make this more organic let's kind of use all those spheres together and maybe smooth them a bit and the easiest way to do that is to use a VDD and a BD b is a volumetric representation of a geometry if you want to learn more about pdbs and the general volume techniques we have a nice premium course on that but for now let's just drop down a wee DB from polygons and we wire the solver into that and highlight it and immediately you see this really coarsely resolved volume here so let's increase the resolution by decreasing the voxel size to say 0.025 takes a bit longer to calculate but here's this higher resolution volume here let's smooth this using the SDF node that comes with DB DB toolkit here so why are listen here highlighted and yeah the default settings look kind of fine you could increase the iterations or the filter box will radios in order to blur this even more let's convert this back into a polygonal mesh for rendering using a convert VDP node to a wire and here highlight and set it to convert to polygons like so so this resultant is really high risk polygonal mesh and if you don't want these measures as high resolution you could increase the adaptivity a bit so Houdini tries to poly reduce this however sometimes with animation this introduces a bit of flickering so we just leave it at zero because honestly this is not that extremely high-risk and before rendering I still want to smooth this surface a bit to get rid of any jitters coming from normal errors using an attribute ler which by default is set to blur the individual points positions so if the wireless in here highlighted maybe set the blurring directions to four again this smooths out the whole mesh a bit more let's reset this hit play and you see it's not that fast because well that's actually benchmark what is the slow thing here so let's reset that also let's reset the simulation so this isn't cached anymore and let's go to the performance monitor here and hit record and now let's play this simulation again and after we stopped this and maybe we stop this here as well you can now see this colorful highlight here telling me which nodes are the slowest in my setup and that's definitely dvdp from polygon so then the BTB smooth SDF so this VDP workflow here slows us down a bit if you guys like what we're doing and want to support us you might want to head over to our patreon and we'd like to thank all of our patrons especially rific on at all Chrissa bear important looking pirates on Quora VFX Patrick Jillian and gearbox studio Quebec thanks so much guys

Channel: Entagma

Views: 29,076

Rating: 4.9790797 out of 5

Keywords:

Id: NqdnTXuxn6k

Length: 6min 7sec (367 seconds)

Published: Sun Feb 02 2020