BIG FIRE | Houdini FX Tutorial - Full Scene Included |

[Music] hello everybody and welcome to the big fire I was getting a lot of requests for this one so it's finally time to show you how it done also I'm going to be giving you the hip file and the nuke file for you to test this out on your own uh I assume what people liked with this one is how sporadic it looks it actually feels like proper fire fire is actually quite fast and it moves very aggressively so I feel like this kind of Hit the right spot between um all of those elements so yeah let's see how how it was done this is a comp and what uh what we're going to do is I'll do a high level overview and then we're going to do a deep dive on everything the comp this was rendered with Arnold but what I'll going I'm going to be showing you how to do this with Karma so this is what we get and then we add some motion blur motion blur always helps this was R rendered with motion blur but adding just a bit of blur on top really helps especially because this render has a ton of noise but when you put some motion blur on top a lot of that goes away bit of color correction nothing special just to reduce the contrast a bit using this uh great aov Gizmo to just darken the HDR and then merging on the Embers so the Embers are I was just rendering them separately adding motion blur on top even though uh we don't really need to because they already have motion blur or we are uh faking the streaks of motion blur that you would get with Ember so let's see honestly this would have worked without potion blur then doing a blue key here on the alpha you get this so you do a ke plug it in go here and grab the blue here and what that will give you is you can then brighten just these areas so blow them out just a tiny bit and that gives it quite uh gives it a bit more punch but also I guess looks a bit more realistic uh if not everything is like properly exposed so that was the thinking and then some Luma Grain on top because the because uh it just uh I like grain just makes things look a bit better and then what I was doing here is just rendering out different compositions uh for specific areas so that's when it comes to uh the comp it's very simple straightforward let's jump into Houdini hello there if this video is of any value to you so far please consider sharing it to to the universe it really helps us a lot and we're going to make more content like this in the future so if you like axm and you like Houdini and you want to see more content like this in the future it's going to help us a lot cheers back to the video okay so we are in Houdini this is the entire setup and let's start from the top shall we uh this part is where we do the emitter this is how the emitter looks like so it has a few different levels so let's see if I disable them we get actually let's do this so one emitter two imits and then also the third one and then once you combine them you get quite a lot of nice variation on this side we have the tiny little um noise patterns on the ground and then you combine all of them and this is pretty much our emitter then this is the fire simulation area so this original Sim was done with axium 3 uh o this is pretty much the Sim kind of similar setup done with 3.1 and this is another example that is much much faster because in the other ones I'm using four substeps in this one I'm using one substep much faster to sim actually I think this one takes like a minute all of these ones uh are going to take five minutes and are really heavy on the vram but they give you like uh the ultimate kind of details that you would need but this one is not bad so I will show you how all of that works then this is where we do a our smoke Sim so essentially we just get our low reses fire this is uh just the temperature of the fire and then we do a smoke Sim on top of that and this is how the smoke Sim looks like absolutely nothing special about it very simple and then down if we go down the pipe uh this is the render area I'll show you that later this is just an extra thing if you want your simulations to Loop uh if you want looping fire looping smoke this is uh the way to do it uh nothing too fancy here you can explore this on your own uh I can talk about it later but nothing too fancy happening here and then at the bottom we have the Embers so we do our low rest smoke we always need velocity and then we have our low rest fire temperature we combine them do a postprocess so all the fields that are the same here you can see they get merged and then we do our ambers look at those beautiful points and then um we Trail them and add them and then do some color on top and do one one version that's super small and one version that's a bit longer and then polywire and there you go done good good quality good quality ilm Style Style Embers good stuff all right so let's start at the beginning I guess uh this is the the emitter so how it's done is we do a circle you create some noise so this I like this because it gives you you can then do a lot of different variations of this right uh just to so then I transfer it up just so it's a lot bigger so you can see it's almost like it's a big fire that's what I'm that's why this is called big fire because this is almost like freaking 20 M uh wide uh which is quite a lot uh but you this you know you do can do it offset and you're going to get a different type of fire so this is very easy to do multiple variations so once we have that uh on this side I just create a density and temperature attribute and then give this a p scale of zero okay keep that in mind on this side I have a sphere I noise it up and give the spe the sphere a p scale of 0.02 then I transfer that attribute we transfer the P scale value and if I copy points uh sorry if I copy a sphere just going to make it initial size bigger so we have our points right and I'm just deleting a few just so we don't get too many spheres but I guess we can do this and with this attribute transfer we're transferring P scale 0 and 0.02 and we get something like this so This has a nice gradual fall off that's happening to Absolute nothingness right and that essentially gives us this you can see there's a nice fall off that's happening we don't have this well if we so annoying there uh this is how you can control this all right very simple stuff and all this has is a attribute noise that is animated and it's doing this so fire usually comes in it has a a natural flow to it so it's going to [Music] um when it gets hotter some areas of the fire are going to be hotter some are going to be colder and if they're hotter so in this case this area is going to be colder and this is going to be hotter this area will will rise up faster and it's going to uh contribute to the temperature and the buoyancy and that's how you just get more organic shapes and you also get those aggressive shapes that we need uh from fire so then we have another one that's a bit faster a bit more sporadic again just playing um just adding layers usually uh creating effects uh is all about adding multiple multiple layers and that makes it look more complex and then another one that's super small and just uh yeah it helps you know you can experiment with this this is just what got me to this result but once you have the file you can then do whatever you want and experiment with this so then we combine them and for some reason oh here we go yep yep so we combine them here you can also add a point velocity uh keep in mind you do it while we are still on the points and that's going to look like this uh in this case I was not using velocity in the Sim but you totally can and then you ruize everything you get something like this on the other side uh this is for the tiny little noise patches those are these guys the small ones and that just gives it um scale and it's more interesting um just gives it a more interesting art direction as well but it does help with the scale to have like some really tiny flames in comparison to the big one you could also simulate this separately and simulate this part separately and then just combine them cuz sometimes these ones they require a much higher division size the resolution I mean of the boxal needs to be quite high for these ones to work and that's why these uh The Sims in this case usually take like 5 minutes which is uh quite a lot I guess for especially for axium simulation times but this one is super fast so you'll see that soon but just you know in this case I combined them I cach them out all good simple then on the simulation side I just put down a collision plane so it's just going to do a plane Collision now for anybody who's not super familiar with axium I will try to recreate this one from scratch uh but we also have a axium fundamentals course that you can check out and I I kind of go through a lot of fire setups there but keep in mind that the setup and everything below and on top can definitely be used with just the vanilla pyro that comes in Houdini so everything everything is everything can be applied to that so these are the settings for axium uh 3.0 again because you're going to be getting the file you can play with them but nothing really fancy I'm not using combustion just a bunch of disturbances uh sourcing is very simple and uh substeps are set to four because sometimes with super fast moving fire uh you you sometimes you do get some bending that's happening uh but that's why if you put the substeps to four all that is going to go away and then also the simulation the time scale is set to four time scale essentially just multiplies everything up by four you can do it manually but this is just a global multiplier for everything and it's going to make everything move faster so because this scale is quite big if I didn't set this to four the fire was moving a bit too slow um all right so this Sim is quite heavy in terms of voxal like there's a lot of them you can see uh like how chugging how much my viewport is chugging on this there's this is super high high res right but I also have all three fields um and we can visualize this with this spiral look yep and it's going to get slower also I need my vram is completely false so that doesn't help oh here we go all right sweet let me I think just need to in it so Pro tip um if your vram is getting full just disable this enable it it's going to uh flush out the vrm and yeah that's that's the original Sim that's literally the simulation it's the same cache from this render looks like this super slow now we we are approaching uh a lot of axles so let's see so this Sim itself has 150 million active uh voxos and then obviously when we add the Pyro look it's going to create a few more and especially because I'm creating the uh the C the color field here as well so super detailed and this is how the Shader looks like you creating this curve so we get the nice uh dark Pockets that we usually get with fire and one of the tricks here is actually using smoke if I disable smoke sometimes fire looks very cool on its own uh but here's the trick it's very hard to composite fire because here it might look cool and when you view it on a black background it's still going to look very cool but then you start composing it uh putting it into a shot and all of all of a sudden you'll see that it kind of looks transparent and it's hard to composite it in and then you have to do a bunch of uh tricks to make it look good what you can do is just render it with some smoke in this case it worked when I increased the density super high and create and just put smoke to a almost like Black color and that will fill those black pockets and it's actually going to help if you composite this into footage this will still be black because this is actual actual density uh maybe this is a bit extreme but that's how I was able to get this super crunchy uh crispy chicken type quality happening in this render so this is the this is the trick this is it all right so as you can see this is super slow uh this one is I just recreated that setup with 3.1 and it still has a bunch of voxal so for fire you do need to be super you need a lot of voxos for it to work actually this one has even more voxos uh but it's still it's still going to take only 5 minutes is to render uh to simulate on my 3090 uh uh one trick a lot of people I saw if they're upgrading from 3.0 to 3.1 uh if you go to axium there's this thing you can enable to switch between versions if you have both of them installed uh I believe it's this so This hides or always show and that way you can switch between the axiim versions just like so when you do that it's going to change a few things because you can see in 3.0 all of the TS here are active when you go to 3.1 only the the ones that are checked are going to be active here and the solver runs a bit differently there was a bit of a restructure on the inside so you will have to change your values to get back to your um to whatever you had at 3.0 but 3.1 is just faster in general and better so I advise you to do it all right so let's see how we can get this I believe this is going in the other direction so this fire I do have a preview here this guy oops that was a lot of previews but let's see if we can recreate this and these are the other previews that are very slow to make uh this is this is the 3.1 fire and this is the 3.0 fire 3.1 maybe this is a bit uh goes a bit higher up and then let's try to do this one but this one is super fast to simulate well not that fast hello there if this video is of any value to you so far please consider sharing it to to the universe it really helps us a lot and we're going to make more content like this in the future so if you like axim and you like Houdini and you want to see more content like this in the future it's going to help us a lot cheers back to the video still going to be pretty fast uh when I'm testing fire I do like to test at quite high res uh but if you if you cap it at like 20 30 million voxel so you can just start seeing the details that that's pretty uh that's a good place to be in so yeah like 30 million where we are right now and we have density and temperature in this case another Pro tip when you are testing out things uh so obviously when you when you look at fire it's good to uh look at it through the Pyro bake but you can kind of see you can kind of see the shapes right you know it's not going to they're not going to be exactly the same but you can kind of see them here so what it's uh what I like to do is just disable everything but just keep on the density and that will make the simulations even faster because it doesn't have to cach out the other fields and write them to disk because uh the writing to disk part is actually slowing things down a bit uh obviously so yeah that's just a faster way of testing it out so but you can also you know we can preview it here quite fast as well so the way well let's uh let's try one right so let's do a axtion solver let's see if we can make something decent from this so just going to plug this into the source shape as a glider and then this is our emitter in this case to make things go A bit faster so this is our emitter you should use the high-res version for your high-res Sims uh but what you can do is you can low res it a bit down reses it and it's going to be a bit faster and it's going to be faster for you to do iterations which is always in my opinion the most valuable thing is to do fast iterations so let's see garbage we get absolute garbage so all right first off output disable everything go to solver put this to 16 bit it's not going to change anything but your files are going to be smaller the you will not see a uh any difference next thing we can do is increase the temperature so that's a bit better and then let's add wind going to put 35 wind that's going to make things go to the left a bit and then what we're going to do is increase the time scale to four so now everything is multiplied by four that's cool but see this solver frame step solver frame step this means that this is going to be affected by the time scale in this case I don't want that I want this to be separate and not affected by the time scale which means that so if you leave it to solver if we put this to 10 the decip is going to be much higher so which is maybe something you want you know this also looks like uh fire so that might work but in this case I want this to be not affected by by that all right still doesn't look exactly like fire um this put this to four maybe increase the did I increase it or decrease it yeah maybe 35 something like that kind of looks okay was I had four here as well let me just quickly check yep four I mean can try five just to see if five will essentially make the wind stronger and also the buoyancy is going to go up a bit higher uh now we can check our disturbances and oops here we go um complete disaster so you can see with uh time scale our disturbances are going to be affected as well right so just lower that bad boy down quite a lot still too much one it's probably still a bit too much maybe add another turbulence and also turbulence I usually put this to fast perin because it's going to be faster to compute and let's see put the speed oops not that high maybe to eight and then the second one I will make this a lot bigger and then maybe put this to six so the this turbulence if you test it out it should just blow things up quite aggressively up and down actually it's not that bad so it should feel a bit aggressive um let's see so we need to go down to three to actually then start seeing the details otherwise uh the disturbances feel quite aggressive so looks okay maybe put this to seven this down to three um you can check on confinement if you want sometimes it gives a nice tiny detail we can get more details out of that like that point C put Point C2 bit higher maybe more wind so it uh it's going to with more points it's going to lift higher and also faster so it's going to feel like it's going faster so we have something like that let's do a cache to quickly preview it and what I forgot was we do need temperature now cuz we do want to preview it with the pyrro and these I mean these are quite still low resolutions right well what is that well I guess we are already using 40 million boxal so it's not nothing but but in comparison the other ones were in the hundreds uh of million so punch this in let's see this is too much whoa whoa whoa whoa calm down so four five maybe go down a bit with the smoke maybe six and let's do a quick preview so I know it kind of looks spotty here and it feels like there's a lot of noise where are we previewing yep uh but all of that gets um it's going to go away in the render and most of that goes away if you add motion blur and stuff like that so it's just a matter of testing but you can see that you know we made a decent I guess looking fire uh now it's just up to tweaking this making it a bit faster making it a bit slower also uh making the Sim more highrisk so let me let me try do two and also I think I liked think I liked more more turbulence for this to one this to two yeah actually let's see let's put this to 50 just want to see what happens go back to five this is how I'm testing I just I just see how it's influencing it so that's a bit much right 50 is too much but we know it we know it's working let's back to 10 so see I'm looking at these like like woof woof like big whooshes and that makes fire more interesting it's pretty good let's do a preview like that just so you guys can see this is how I'm thinking when I'm doing fire also I'm doing the biggest sin ever I'm I'm not looking at references right now which is something that I would always recommend for you guys to check if is references so because our turbulence is quite High we are getting some uh noise at the bottom because it's colliding so I'm thinking go back to five it's not going to be visible in the final render I think but also what we can do is lower the Collision to be minus 0.5 and that helps a bit so it's not I think we were cutting off our emitter a bit because our emitter is yeah it is a bit in the ground so we were cutting it off just a tiny bit maybe maybe it's a bit too high now maybe don't go as crazy with the buoyancy and maybe increase the disspation yeah it's a bit high but honestly with all the with all the smoke later and also this is still a midr Sim uh for the highr one yeah we do you do have to wait like 3 five minutes for it to complete just because fire needs to be super high res but this gives me that same kind of feeling that I was getting here you know it's very similar similar Vibes yep it's pretty good all right so I'm going to leave this to you guys to experiment and do your simulations uh on your own but yeah just keep in mind when you actually then start doing your finals you will have to go to like5 and that will slow things down we can do a we can I can quickly do one and also I will disable I will go to the highres emitter guess that's going to help a bit all right 60 frames that's enough 3 minutes not the worst let's see what we got o it's a bit better super high rate is that 250 million what is happening but yeah uh we are that's an okay Sim I think it has an okay amount of details so yeah looks pretty good looks decent that would uh probably work I'm not going to pre preview it because it's going to be super slow but that's what you get so cool experiment this on your own let's continue so after you have your sim done there's a bunch of things that we need to do yeah this one's going to chug oh my God Sweet Lord the first one after you have your sim done I'm going to go more towards the beginning because it's going to be faster okay not that much faster turn this off you need to I'm going to go down here don't worry so you put down your pyro pyro look pyro and you do the curves you do the curvies like so these are roughly the values that you want um I don't know oh okay I was baking this for Arnold I don't need to bake this this anymore silly silly Arnold so you do this and then you go to Quick setups and create render sage and then you click on default and then accept that will create this so it's going to already link everything where it should be I'm going to go a bit forward in time now so it looks a bit better yeah I guess uh so it's going to give you this but obviously I modified this yeah sweet no I modified it uh but you will get your fire in and it will already create the render geometry settings it's going to link it up automatically and it's going to create a material Library that's Al also linked to your pyro which is very convenient um so in this case I wasn't changing anything on this side so you get your fire and if you render it it's going to be fiery um I changed the volume velocity to three just because I felt like it needed a bit more um motion blur what I did change was I set this to slf Fire and that will create um if you go to the Orion Workshop I go through a lot of these Solaris tips and tricks that you can do but yeah essentially this will create this fire thing you can type in whatever you want and it's going to create this uh naming convention fire and here the material path you want I created a material fth slf fire just so it's a separate material path because otherwise if it's not separate when you're merging them because we have a separate one here on the left it will combine them and you don't want that and then on the left we have our smoke bringing it in in the same way applying the Shader and combining them right so here what you can do is what you can do is if we go into the material library on the smoke we can use the scatter to fake the fire elimination that's going to be the fastest if if you want to do it for real you can go to the render settings here and say yes to treat as light and now your fire is going to be a light it's going to look better it's going to be much slower so I I'm like hell no and go back here enable scatter you can see it looks a bit more janky it's not exactly the same but you know what it's good enough for most cases then you sublayer them together and so this is the fire and this is the smoke okay I will go through the through all of this in a second just so you know how this is created just give it a second to load because are these are big big VDB files so this is where we have our fire and then what I do is I don't really need density I only want temperature so what I do is I remove the temperature rename it to density um you can then remap your density values if you want and then I combine my temperature velocity and density here do a VDB resample and this is how this looks like if you want you you can remap your density or in this case your uh temperature values and all of this is going to be your smoke emitter so we are using our fire to emit our smoke and that will create uh first off we're using the same velocities from our fire and we're also using the temperature from our fire where the smoke would actually then be emitted and that will give us something like this and it doesn't have to be a super highr emitter that's why we are bdb resampling it down after that we just plug this emitter into a new Axiom so you can see this this right and it's going to be using all of the good stuff that you get from your fire uh nothing special here nothing special here except I was using pull on the velocity um that just gave me the most proper looking velocity uh without it being too extreme so if I if I go to add in some cases this was pushing the smoke too much uh almost like unnaturally so you can see like it's really going and it became super mushroomy and then it's you know we have to deal with all of that so if you put this to pull it will not go as crazy but it it it's still going to respect how fast the velocity of the fire is moving and it's just going to in this case this was the setting that worked for me the best the smoke nothing special just I just turned everything on and smoke is not the main thing here so don't worry about it um you need velocity only if you are uh if you're going to be rendering motion blur otherwise you can turn all of this off and it's going to be way way faster to preview and it's going to be way way faster to simulate and to cash out so after you do cash it out going to get something like this now this smoke is not the the the best smoke ever made uh it it was just it did the job so but I don't particular particularly like it but it was okay and here what I did was another pyro bake just to see where the temperature illumination would be happening and then again quick setups um create render stage default accept it's going to do this okay the reason why I did this was because then I went inside of here you can see it this is the default setup it gives you stop the render and then I just copied this and I copied it into the previous setup that I was showing you before okay so it's just a small little shortcut so this is the main render where I copied the everything from here cool sweet so once we have our smoke I do another VDB resample cach that out so we have another lowr version of the smoke and we use this for our Embers so in this case I have our smoke we have our temperature fire combine them fire process to flatten all the fields um not sure why I needed this but maybe it just wasn't picking maybe the velocities were not properly picking everything up and the um honestly I'm not sure but I guess I did need it for some reason maybe the it helped with the pop adve um don't remember this second but we be activate uh blasting out the just the temperature uh remapping it a bit and then to do this and then uh the remap essentially just creates a hollow temperature in this case because if you don't do it it's G to scatter it all over the place but I only wanted to scatter it kind of on the outside and then yeah you scatter points from here we have our velocity right velocity and using an attribute from volume I copy the velocity back to the points and that that will give you velocity that doesn't look proper yeah here we go yeah it helps yeah that's how it's actually going to work so uh do a blast so you only have velocity otherwise uh you just need to do it here so now it's going to work but it's going to be faster if you plus it so velocity that's how uh copy that's how you copy your velocity from volumes to points and then you do a pop Network also we're still plugging in the velocities into the second input for our pop atect by fire and yeah you get points that are aded by the velocity coming from from our fire and our smoke cuz we if you remember we combined them then I do a pop Force just a lot of um one for big amplitudes big swirly sizes and one for small swirly sizes uh a pop drag so it's a bit more so it's not as chaotic uh pop drags and all of that you have to adjust based on your scene how big your fire is how fast you want your particles to move and then a popet effect using the update velocity in this case everything else is stock so here we go this is the these are the points that we get and [Music] then deleting of few of them I feel like something is slowing my viewport down quite a lot okay so I restarted Houdini CU yeah it felt like something was super slowing uh the viewport down because it was lagging on just simple points uh so I don't know what that was but yeah then we delete a few points just using IDs random IDs deleting it here and if you're deleting by IDs you don't have to worry about any poppings because every Point has a unique ID uh time warping and then trailing you need to Time Warp because every when you cache and if you don't catch the substeps um you need to just get all the in between goodness with a um time blend so you get this and that means that you get nice curvature coming from your points uh adding them based on ID and then we do a CD and pscale ramp the CD ramp is so we divide age by life and that will give us a normalized age you plug that into uh the CD ramp so the age you can see when they die they go from super bright to Yellow to Orange and then black and then they die right and then this is for the P scale you can then multiply your P scale so when they um when they die based on the age they're going to get smaller and when they're more alive in the beginning they're going to be a bit bigger and you can see that when you actually use a polywire you can see with this power this is where we are controlling in the P scale so I put this to three some of the lines are going to be super super tiny super thin and then when right before they die they're going to almost disappear into nothingness because we are multiplying it uh with the with the age right so this is the ramp P scale that is being multiplied down and then you can also re resize this but you can see uh every everyone is going to be complete go go to complete zero when they die off and then a classic flow noise on top of that just a basic simple anti-alias flow noise adding it to position like that just gives it a bit more interest to the Sparks like that on the right we do the same but I just keep way more points Trail them and then I just keep them a lot smaller so uh the trail was these ones are longer these ones are super tiny and then you combine them to get a good variety of different Embers and then polywire and that's it that's pretty much it and then I copied this path just control copy and if we go back to our render we go to the this guy go inside it's going to take a while yep here we go and we bring them in so stop import you copy this path not twice just once copy it call it SL Embers just so when we get it here it's uh under uh component slash Embers do a basic Embers simple principle Shader and just set this to use Point color and set the emission to one sublayer it together on the left we have this grid which is literally a grid with a UV applied to it and then in the material Library I used a mega scans concrete uh mix material that looks let me let me go to the render but I'll just disconnect the other parts disconnect here we go so it looks like that just has some variety you can use whatever you want honestly but this just has some variety when it comes to uh I'm just using a specular roughness and then a normal map and the specular roughness looks like this so it just gives it a bit of variation but it it's super not important uh for this tutorial uh this is just for so it looks a bit nicer for the presentation purposes right and then you plug this here and it's it is going to be a bit slow uh the camera set it to 80 point it down a bit uh it's cool if you used a HDR I'm just using a I always for almost every project I use this Sky uh Sky 18 HDR and it just gives me this blue greenish tint that I like it looks usually looks quite cinematic but you can see it's a bit this one is a bit slow to render uh it might be interesting to see how this would look with uh carax xpu cuz that would be much much faster it's going to be probably well see I'm not even rendering motion play at this point but it might be faster if we honestly if we go to Just divide this by two just so we see something so yeah because we're using the smoke that we got in the fire itself you can see we get these dark pockets and that creates that crispiness and then this looks okay but then you need to enable motion blur to get a much nicer um shape to the fire and then in compositing I also added additional motion blur on top but you can see you you enable motion blur gets a bit slower to render just want to see if it works properly and put this to 10 just want to see if it makes a huge difference yeah it does work okay yeah maybe even four cuz you do want these stricky streaky kind of lines happening in the fire and sometimes that's just yeah just you need to increase the motion blur a bit but yeah I think that's it guys um I think we went through the whole setup you can play on your own uh I would advise you to maybe do a smaller fire it's going to be much faster to sim much faster to render and then once you're Comfort comfortable with smaller fires you just scale up to the uh two big fires but yeah that's it that's how this was done yeah it's pretty much this and then yeah with compositing you put some more some more motion blur uh maybe a bit of glow would also help in this case and yeah that's it just the right angle and you're good to go all right I hope you guys enjoy this um I have a bunch more fire tutorials that I can do in the future so let me know if you want to if you want to see those as well uh but otherwise we have a we have a bunch of exciting things that we're going to be adding to the tutorial and workshop Library so stay tuned all right bye everybody

Channel: DoubleJump VFX Academy

Views: 10,349

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Id: nJa5RbQK9zU

Length: 52min 36sec (3156 seconds)

Published: Mon Jan 15 2024