Tutorial 3 - Rain Systems and Wet-Maps

[Music] welcome back to the third Houdini tutorial from 9 between and today we'll be going over how to create this effect now the serene effect has a few layers to it firstly we'll be creating a pop network that emits particles and from the collisions of those particles will emit a couple of things firstly we'll do some splashes and after that we'll do some running particles and run along the surface object next or copy geometry to all of those points and then finally we'll create a wet map so I hope you enjoy in Houdini let's begin by dropping down a geometry node alt click and drag this node it's duplicated first we'll rename our geo 102 rain and OTO 2 node will rename to Collider dive inside of his collider node and delete that final node next we'll drop down a rubber Toya and this will be our test geometry so next we'll drop down no plug that into our no and rename this doll Collider underscore up jump back up dive inside of our a node and let's drop down a grid this grid will be emits a for our particles so we can just resize this to a 5 by 5 grid and move it up 5 units on the y-axis next we'll drive down a top Network and plug this girl into the first input dive exact spot Network give ourselves some space by dragging down this L trip node and in between our pops over an output node will drop a gravity force and in between a gravity force now Bob solver will drop down in merge next we'll need to merge in our Collider slow will create a static object and merge that in an unarmed urge node let's switch these inputs because left input effects right and we want our kaleidos to affect on the ring so under static object go to your son paw go to your Collider choose Collider out as Minsky it brings it into the scheme now we don't actually have an accurate representation of our collision and we can see this by going to our collisions tab and activating the collision guide if we hide our geometry we can see that this is a very inaccurate representation and we need reasonably accurate representations of our geometry if we are to be doing things like splashes and running of water so the uniform division is 280 with your physical and increase the friction up to 100 can hide our vision and display all geometry again now we can begin on actually creating the rain so once again get ourselves in space by dragging this up here I'm pulling I'll merge you know dawn on our pop source we'll go over to the birth tab and as you can see we have it set us 5000 for now and that'll be good but we can change it if your computer cannot handle a high particle card oh we can drop this to 2000 now and if we play this back you'll see we have particles falling from our grid to your timeline and activate the real-time toggles it plays back in real-time one thing you'll notice are these lines and fall and the reason we have these lines is because when we have fast-moving particles and they move a large distance between two frames Houdini does not account for that travel we end up with these strange artifacts of lions appearing to get rid of that we can increase our self steps by diving up and going on tell pop network going to our simulation tab and increase in the sub steps to five we dive back inside well I've sorted out our issue so the next thing to do is to drop a pop collision behavior - I got in and we'll give us a group name of hit now a pop collision behavior nerd checks where the particles are interacting with a Collider just hitting it and then we can do particular things with that so in this case we're adding it to a hit group and we're also coloring those particles red but when we play this back and let's set these particles aren't getting colored red so on our pop solver if we go to collision behavior you'll notice that there's this ad hit attributes toggle so if we activate that and then go back we'll notice but now all particles are turning red you can't see that you just press D it's a geometry and increase your point size to 10 and I can see that we have some particles that are turning red you that we have particles colliding and those collisions are being registered so what would we like to do with those particles well first we'd like to have a response and we'd like these particles to die on impact but now we have a group that we can work with called hit group so we'll be using that jockey first let's keep working on our current classical set up so next we'll drop down a pop for angle and in this pop wrangle we'll just say at bones equals one next we'll drop down a pop wind with an air resistance of 9.5 altitude of 1 and a swell size of 5 what I'll give us is some general movement you know pops you but we're gently that emulates rain quite well next we'll drop down a tough group and this pop group will be called Maine called Maine activate preserve group and enable this rule now the reason we're grouping these particles is because once we leave our pop net we would like to have access to the particles that are falling so that we can attach a geometry to each point so the last thing that we need to do for this first stream is to drop down in puff to kill node or place it after our murder and we'll use a bounding box enable bounding what we like to do is kill all particles below our Collider so we'll drop the center to minus 2 on Y axis and we'll give it a size of 10 by 1 by 10 now any particles at fault beyond our Collider will be killed let's save space during our simulation now we can go on to creating our splashes so we'll be using a hot stream and we'll use our source group that we created called KITT group so what this does is it creates a new stream of particles based on in group and we already have this group that we created with the population behavior so when particles collide with our geometry they get sent into the stream so in this stream we can run a pop replicate the plug will stream into its first input of your pop replicate and we'll go over here to the constant activation switch it off turn down our constant birth rate give it an impulse count at five next we'll go down here let's change our life expectancy to no 25 and what that will do is as particles hit will emit five particles have a lifespan of 9.25 so we can plug this in to see what that looks like as you can see we have these particles colored red appear to be emitting in a large area and the reason for that is under the shape tab we have this shape sphere now we would rather have our points emitted from a single point of impact rather than from a sphere we change this to point now when we play it back upon impact we'll be emitting five points - hi so go over to your attributes these add to inherited velocity set back to north point two-five a radial velocity goes up to one and we'll put more point five variants on each axis once again play that back the splash upon impact and the reason they carted red is because they're inheriting all attributes from this first stream from the group called hit group and hit group we still have colored red so we don't have to color our hits we can switch that off and that'll do around splashing next we need to just do a few things to this pub stream so I'll drop down your angle we'll say app bounced equals one and then we'll do a pop group pop group we will call splash once again preserving the group and enabling in the rule and so now the stream will all be grouped into the splash group while the first stream will all be group into the main group now we can move on to creating our running effect because now we have particles that splash upon impact we would like particles that run down the surface upon impact to do this we'll be dropping down on top screen once again will activate the soulless group and call the hit group next we'll drop down a popper at the gate mode and peugeot pop scream into the first input now we won't be using constant activation and we won't be using a constant birth rate we will be using impulse count and we'll set that to 1 and what that'll do is on impact join with one point based on our hip group the next we can drop it life expectancy to Norway not five and once again we would like it upon the point of impact so set that to point and not attributes we won't inherit anything we'll set our initial velocities north bank one on each axis so now that we have that set up what this will do is as a point collides with geometry a new point will be emitted at that point that has a life expectancy of naught point naught 5 so what we'll be doing that that is spawning points off of that in our next path the tree and that will run down the surface so this is just setting where we want those streams of water to be running from it's been go ahead and drop down a popper angle and this proper angle same as before until at Bart's equals zero this time and the reason for that is we don't want these particles to bounce off of the surface we want them to stick and Houdini recognizes this bounce attribute within pop networks so we can't just call it straight at bounce equals zero next let's drop down a pop collision behavior again bug listen tell pop collision behavior and we'll give this group name run spot or preserve the group hits understand as a response will make them stick to the surface so we can go ahead and plug this into our merge node and begin on our last stream so create another pop stream and another pop replicate pop stream into the first input of our replicate and let's go to our pop stream once again source group will activate but this time we'll be using the group that we created in our second stream and that was called run spawn over here we'll just say run spawn and now we can go on top up replicate the oh no pop replicate we'll do an impulse cut one no activation I know birth rate or constant and we'll give it a life expectancy if you next we'll go onto our shape and for shape we actually don't want them emitted from a single point we like them with some variants so we'll limit from North Point not one that's just the scale of the sphere that it's emitting from next we can go over to our attributes and we weren't inherit any of the attributes we won't inherit velocity initial velocity to no point one and that'll be the variance so next you can go ahead and drop down another angle and again as they act bounce to zero then we can drop down a pump property and what a pot property is used for is for initializing attributes that we Dini recognises so the one that we'll be using is on the dynamics tab that's called pling it will set a claim of 100 and what that'll do is it'll make the particle stick to the surface of the geometry this area is just the strength to which it clings and this will be different depending on your geometry and what kind of rain effect you're going for but I find 100 works quite well next we can go ahead and drop down okay puck to vision behavior are your property into this collision behavior and this crew pain will be called run we can color these heads to see what they look like so we'll make them light blue and this one will be using slide as a response and again we'll be preserving our group as we've done before and the next thing that we'll do is we'll drop your puck interact there is a position force of minus 0.2 and a velocity force of not point to and what this does is position force is a force used to push particles apart if we make it a negative force it becomes a force that pulls particles together and rain tends to gather so we would like this to be a force that pulls particles together but not too much of a force that they immediately clump the note point or negative nor point to is a decent number to work with velocity force causes particles that are nearby to each other to blur their velocity so they tend to share velocities and so that replicates droplets of rain quite well next thing that we'll do is we'll drop down on hip-hop drag and on this pop drag will set up tip 10 and then we can finally plug this pop dragged into a merge node press alt to lay everything out and I'll display a flag on our output I pay this back to see what happens so if you look closely we have these light blue particles that slide down the surface once again press D bring up your point size and we can take a look at what's happening now so when we played us back y'all notice some particles hitting and rolling off of the surface and that more or less looks like droplets of rain so what we'll do is well jump up out of his Network trap down a file cache nerd I got pop nets into this find a place to save a rain cache here to my ring thought great a new folder called cash and in here coldest rain particles dot dollar F F dot B GE o SC so dollar FF once again that's the corresponding frame to save because if we don't have this it will only save one file and we'd rather have a sequence saved but B GE o SC is what I found to be the best I'll type saving geometry on pop net so that's what we'll be using for this one having a switch on load from disk so that once it's saved to disk won't be calling this every time but rather just fetching from our file cache and the last thing that we'd like to do before we actually catch this up is to increase the number of particles I've been using we can go to our pop source increase this to 5,000 finally the disk then once the particle we can begin copying geometries in these plans so we'll drop down is still said I'll display flag on the sphere can't you take polygon mesh will change its rows to 5 and its columns to 8 and that gives us a faceted sphere so the next thing that we'll do is well drop down and edit node go here select this top point and we'll move it up just until this resembles a raindrop next we can drop a copy two points and we can plug our rain particles into this now currently it's copying to the collider geometry that we've brought in so we need to just choose which points we would like our sphere to be copy to so over here we can choose our main points and if you remember those all the ones in our popular that are just falling we have a splash group we have a run group and we have this main group so for this one we'll use the main group and if you can't be two points these points are currently massive so to fix that or dropped on an app to attribute dry angle between our file cache and our copy to point in here I'll do two things firstly we'll say at orient equals V V and then we'll say at P scalar equals not point not one and semicolon there we go so what that does is this orient equals V at V so that's our orientation of our particles to face the direction of our velocity so if we have velocity moving slightly to the side as you can see on a lot of these points and they'll face that direction and so that just gives it a bit of variation that makes it a lot more accurate in terms of how it looks then our P scale is just setting the scale of our points so we can change this depending on the scene so I think for the angel I use naught point naught naught v then I just up the amount of particle that we had but we'll keep this up north point naught 1 for now just so we can see all right you can drop down you know after that plug that in there rename this no mean underscore next we can move on to working without splashes snowball drop down another sphere said I'll display flag to it again once again set it to a polygon mesh this time we'll do 3 rows and 4 columns and then I'll drop down I'll copy two points plug it into the first input and plug our file cache into the second input on those copies points once again we'll choose the correct group and this sign will be using the splash group we can set our display flag and once again these points are massive so to correct that another attribute triangle between our copies points in our file cache and the reason that we put this attribute angle over here is because copy two points when it copies your geometry to these points your geometry inherits these attributes so your sphere in each case would inherit your orientation and your P scale so you can make it inherit other things such as color and an up attribute whatever you need it to inherit you can inherit through you so we'll continue and do at least L equals dot point naught dot fire so these points will be slightly smaller than our other points and then again we can drop down a no and call this one its flash underscore so if you take a look you can just hire this flippy collider he's in a separate note just hide all the objects and now we can see what's happening with our splashes hi instancing these points to all of the splash points now our final note is our run group so this one will be doing slightly differently let's drop a tallit note we would like to delete everything except for run so exclamation run change these two points there we go now we have only the run particles so what we can do with this is we can drop down in gdb from particles btv particles there we go plug your heat node into the first input and you end up with this blobby mess the reason for that is just our voxel size and our point radius scale so we'll begin by dropping our point radius scale drop it down to your naught point naught naught 3 5 drop our minimum radius down to no one then our voxel size will drop down to north point on all time the reason I did it in that order is because a lot of the time when you decrease your voxel size on this VDD from particles node without changing your point radius scale you can really slow down the process these two should be as close to each other as possible and if you want accurate representations you'll drop this slightly lower than your point radio scale but in this case it's fine it's the next thing that will do it will drop down a convert BBB and we'll convert from volume to polygons and as you can see we now have these tiny droplets and they may be a bit too small so we can just increase the size of our point radio skelton operate not 5 sorry no point normal at 5 and on the other thing that you can do on your V DV from particles node is change your particle footprint so you can change this from spherical to your velocity trail and as you can see it goes quite crazy and the reason for that is just our settings over here but we can't make this work so what we have to do is change your multiplier to Northpoint not 1 and your velocities basins in or point two and it creates a slight trail so the last thing that you'll need to do is you'll need to transfer your velocity so we'll drop down an attribute transfer node plug your convert VDP into the first input now what we'll be doing here is taking the points from our delete node and feeding the velocity back in because you'll notice something on this convert VDB node we don't have our velocity anymore and the reason for that is when you're converting to a V DV you're losing all of your attributes so we don't have any of those attributes anymore so we'll have to transfer them back on so under the attributes points we'll just select V will change our distance to one point to drop down and now plug the Centaur now and we'll call this one the run underscore hours and once you've done that you can merge all of these together and take a look at what we have so you'll notice a few things such as these particles being too big but that's all to you you can make changes to that sitting over here and change our key scale to 0.05 perhaps you want them smaller and the reason that we use these round droplets as opposed to a longer geometry is because we will be rendering this or you would be rendering this with velocity and you would be using motion blur and so these particles would blur in a streak so you don't have to have geometry that looks like rain you just need something that merely resembles it so once you have that you can just drop down a normal node drop down on your final No call this one rain underscore now and there you have it say if we jump up a level and show our geometry you can play this back and take a look at what happens we have our particle splashing and we have some running down the surface and of course you can tweak all of these settings if you'd like to change this and of course this isn't exactly what I used for the angel render but it's more or less the same so you can get the same effect that I got in the angel just with a few tweaks the last thing that we'll be doing is adding a wet-nap to create the web map we'll be using an infection sulfur and it will be the one that then Watts uses it's quite similar to the one seen in my Phoenix desintegration video but the one that Ben Watts tells is all involved and it's quite useful to have a nother approach to it I do quite like his setup so a thanks to Ben watts for that tutorial and I'll be linking that in the description if you want to check that out so let's dive inside of our collider node drop-down is scatter like alkali out into the scatter one nerd and we'll push up up total current to 8,000 next will drop down an object merge and over here will merge in our file cache from our rain node find a file cache and next will be dropping aide to leave node like your object merge into this delete node and what will be deleting from this is our collider because our file cache cache the collider as well and we don't want to use that so all we'll have to do on this delete node is remove this exclamation there we go that removes all primitives from our object merge so now we only have points next we can drop down an attribute wrangle and over here we'll say at wet equals one point one we can copy over this attribute triangle to the side of our scatter node and I'm on this attribute angle will say add wet equals 0 now we have to attribute wrangles each initializing our wet attribute so the next thing that we'll do is drop down a solver into the first input we'll plug our scatter node and the second input will take our object merge now we can dive inside of our solver and drop down a point into the first input of our point four or plug our previous frame and second input we'll be taking our input to type inside of our point park and we'll be dropping a few things first a point to hard open and we can just duplicate that by holding alt and dragon now or plug our P attribute into the corresponding inputs of our PC opens and into the file input of our PC open one volt lock-up input 1 and up input 2 or going to our PC open to file input next thing to do is to drop a PC filter handle into the filter duplicate the folks are unplug the corresponding handle into a second filter now on both of these folders we'll have to change the signature and the channel so we'll change our signature to flirt and the channel that we're looking for is that wet attribute that we created so what this does is it opens a point cloud and within the cloud it looks for this attribute and so we can do things depending on proximity from this point cloud to this point cloud and what we'll do is we'll add attributes so we'll add the current weight attribute that we have to the existing weight attribute then we'll drop down a bind export and plug the on this bind export we will rename this to wet so that it re export our wet athlete so it adds the two wet attributes together and then re-exported you can also plug this into our CD attribute so we can see what's happening and then on our PC open we have a couple of settings but we'll get back to the short thing what we'd like to do is just flip this so offered our range between 0 & 1 [Music] and the reason for that is it will add indefinitely Omega over 1 or we want it clamped to just a fair point so next we'll just like this footnote into our CD make sure that it's plugged into our input of our mind export you can jump up a level and play this back to see what happens so as you can see an attribute and if you remember correctly attribute for wet is corresponding to how C D attribute so as this turns white that represents our object getting wet this value for wet it's being transferred on to these points and that's great but it's getting transferred onto too many points too quickly so we'll make a few minor adjustments change our search radius down to naught point naught 5 and both pop PC opens and change the number of points down to 5 I'm gonna play that back like works quite well the only other thing that you may want to do is add some sort of drying effect and you can do that by dividing or blurring this attribute for the wet value every frame so we can do that but going back into our 1-var an on this first input if you remember correctly this is the previous frame so this fetches the wet attributes of the previous frame so what we can do with that is we can drop down a divide constant and every frame just divide this slightly so we'll divided by 1.05 go up level and you can see what that does so as it gets wet it also dries or absorbs moisture slightly once we have this we can drop down and transfer attribute plug our Collider out into the first input and a solver into the second input and what we'll be transferring from you is simply a wet attribute so now that we have our wet attribute on our original geometry we can do a few things with that so we'll drop down an attribute angle and plug this into the first input firstly we can say at CD equals channel ramp cassette see a trap we'll just call this CLR color , and then you needed a driving force so we'll use our wet attribute that's at wet and then we can create our spare parameters go up to edit parameter interface in this color node we'll just be changing the ramp type from float to color apply and except that's something that you'll notice if we're just adding extra color over here is that we can have this attribute control our color and that's great because wet areas often appear darker on object and of course that depends on the object you're working with if you're working with something like glass you won't need that but things like cement or that angel that I was working on cement would get darker as it gets wetter so what we can do is just flip us around and set the first value to white and the last input to black and what that will do is darken the areas that are wet and you can slide these around if you want it's to look more wet in more places and you don't have to have this as pitch black you just have that as a gray now areas get wet how's the water hit and the last thing that we would like to do is change the roughness so what we would like is for the wet areas to be shinier so we can say a pure ax equals channel ramp and in these inverted commas we'll say rah that's what it will call our ramp and once again it will be driven by wet so we can create spare parameters and now we have this roughness ramp now an attribute the value of one means that something is entirely rough and has no shine to it so we'll invert this I'll just bring this up to them halfway and we'll drop this down to almost zero I will deny play notes and you won't be able to see it in this view but when you render out all the areas that are wet will be shinier so that's all you actually need to get this wet map working and of course you can make changes to your ramps and that will change how it looks when it's rendered so we can jump back up and take a look at the two of these together and you can go ahead and render this out you would have to do is activate your motion blur on your particles and in your camera settings and once again that's covered in other tutorials it's covered in our Doctor Strange portable effect tutorial and you can apply a glass shader to these particles and that should work so that's all for this tutorial thanks for watching and be sure to give me feedback we'll be releasing a lot more tutorials in the coming weeks we are really exciting things coming up we have a lightening tutorial we have a Rubik's Cube tutorial we have some geoeffective things that we're doing and we even have a carnage symbiote coming up so stay tuned for all of that once again thanks for watching [Music]

Channel: Nine Between

Views: 66,224

Keywords: Houdini, VFX, Tutorial, Rain Effect, Houdini Tutorial, Special Effects, CGI

Id: zHERTeOmm7w

Length: 39min 35sec (2375 seconds)

Published: Thu Sep 27 2018