How to use Karma in Houdini + Tips & Tricks - (A World Ablaze Tutorial 3/5)

[Music] all right so let's talk a little bit more about karma uh so we're gonna render everything in karma i did do a bunch of experiments with mantra as well but karma is just a lot faster but there's a couple of things you need to sort of take into consideration when you're gonna gonna be doing these things um so i think the easiest way to go forward is to just do this in a empty scene first and then later we'll move back into this thing to explain how this all works so similar to how we did it with the pyro and the axiom part so just a very quick basics we're mostly going to be using karma with these uh karma ropes we're gonna do a couple of things here in the um in the actual lob networks but for the most part um a lot of the stuff just happens with the uh with the robs here all right so uh in this empty scene let's first make a uh let's make some fire so it's a simple fireball you know what let's actually just grab our old xcm explained things g we made a little bit of fire there i guess we could just use that one all right so we get got some stuff going on there so uh let's just do a null here and let's call this sim let's make a render node and that's object merge or fire in there for some reason complaining again all right just have to scoop for a couple frames like you would probably cash this out normally but we're just gonna do some basic uh basic things here right no all right you're not doesn't want to all right let me just file cash this out real quick so i mean at least we we can be sure that it's actually there 35 fire right i can just do use dollar hip for now save to this correct all right looked on disk let me put this in render here all right there we go so a little bit of fire going on um yeah so let's start setting some of this stuff up for karma by the way if you want to know more about just regular setting rendering stuff in karma solaris because here we are use mostly going to use the karmarop uh if you want to know more about solaris and my workflow there you can have a look at this thing um sassy snacks v2 moji mojito magic which is of course that developed in partnership with side effects which is about the vellum fluids over and also rendering in karma compositing it's a 21-hour course quite extensive and it's free so um if you want to know more about karma i suggest you check check this out got a good response from it and people seem to like it so you can check that out as well but for basic stuff let's just make a make a grid here just let's just actually type grid let's make it a little bit bigger all right there we go move it down a little bit all right let's make a camera right so we just got a basic thing here oh got a basic thing going on here so let's do a karma rope and or this is very quite similar to the mantra rob it's it's of course there's different render settings because karma and mantra are not the same but you can see it's somewhat somewhat similar in sort of the options here and in here you can select your objects that you want to do you have different render options so uh here you have a bunch of things you can do so candidate objects will be only rendering if the display flag is on similar to mantra forced objects will always render and we'll get into force phantom and this other stuff later and exclude objects will for example even if they are in canada objects and then include objects it will exclude it from the candidate list so stuff like that uh pretty straightforward so let's do do for example uh let's first name our candidate objects let's put our our bovar let's call this it's called rmdr fire by the way and then on the er grid and the reason why i'm using rndr here is for example what i can say is i can type rdr underscore star and now it will grab all of the things that are appended with rndr which is just a general uh workflow tip that might be useful you can open up the viewport there to the camera and now if i press render you can see it will start rendering and um so that's a that's a thing that's in with with this thing you need to open up it opens up a second viewport i wish at some point they will have hopefully have a render view similar like this i would much prefer to just have it in here um you can make that work by the way if you go in here go into the lob network then just make a scene view and then it crashes so i'll be right back so what you can then do is just you can go into your karma rob network you can make a scene view here fewer scene view camera and now we should be able to dive out of it and you can see now we actually do have a sort of a karma karma view going on there so we can just put this to karma and it'll work so like again i don't understand why you cannot why they don't have that as an option by default but you see now it works and we can render some stuff in there um you see if i double click on this now it will jump out of it which is annoying if you want to keep that open you have to actually go in there and then start locking the view to two uh something you would need to keep this open in karma context another thing you could do if you want to keep it like that is you could make a new um where is it a new network view and you would go to out go in here and just link this to whatever like nine or something just go out of it and link this one to nine and just go in here and now this will just be linked to nine and now i can do in here whatever i want and i can still have the karma viewport again i really hope side effects will just make something like this because you can see it's it's pretty simple to just do this yourself so you would imagine side effects could just do something like this and now i have an actual viewport here in my interface which i can use um and i can still navigate through my things here so uh just a little quick tip i guess just pin something there and then it'll it'll work and side effects if you're watching this please make something like this an option so we can actually just have a render view similar to the com to the mantra render view um all right i'll stop rambling on now uh but again like this is this working you have here you have different ways of rendering your scene so default is for ions and you have path traced and you have distributed so variants will fire more samples where it needs so minimum samples and maximum samples if you bring down the maximum samples it will do less overall samples if you do hide this higher do more overall samples will take longer i generally just use path trace this will just randomly fire race you don't really have any control but it's generally uh i found it generally faster than the other things but i guess it would distribute it or with variance if you just put this low it's it's also going to be fast i've i generally have it to path traced i just use the pixel samples here and some of the other things here so this is pixel samples is just the overall samples that you're going to fire so if i make it higher it's going to be longer so if i do guys 24. exceeds fire a lot more samples uh there's also distributed so that's if you have for example if you have a scene with a lot of reflection and refraction you would might make these higher and then just rest lower you can have control over whatever it is that you are that you're doing um when you dive into uh slowers here you can actually like if you build your own network you can actually might do manual overrides on objects we'll get we'll get into it later or you can check out my uh again my course here which goes into a lot of this stuff there but uh you might notice here that the uh there's not like we have this let me make the background dark by the way so we have this spiral thing here and it's um yeah it's quite sort of dark there's not really any bounce light um so this is a thing where for example if i have the render file here let's do a pyrobake again just do by real bake and let's enable fire compute range right so now we're doing the baked volume and then there's the thing called skip let me by the way i want this to look a little bit better let's maybe let's do a visible black body for now just to prove a point uh color ramp we're gonna mostly use the color ramp by the way let me also introduce maybe a light here somewhere we actually have and i need to link these two first frame real quick all right so we have something to cast shadows there all right can one link it back to nine all right there we go let's increase that let's make it a sphere all right uh beautiful but you can see there's not really much bounce light going on so there's multiple ways to do this in sort of in karma the slow way in a more accurate way what i mentioned before with when i came up with the cloud example is actually uh you can see the volume limit here so this is how many bounces are going to be inside of a volume now if you have an accurate volume you're going to have multi scatter so that means that this light is going to bounce through sort of the fox was gonna hit the particles in the fork and then that's gonna uh gonna create a nice look but uh right now you can see this results pretty fast even if i put the samples up you can see it's relatively fast render now watch what happens if i increase my volume limit to let's say two bounces or let's yeah two bounces right as you can see now we are getting and by the way let me uh go to render turn off depth of field here that's a thing where depth of field is oh okay now it's disabled the depth of field was sometimes turned on by default which is weird but you can see this is uh quite a lot slower here now it's actually not as bad as i as i thought but this is a very low resolution sim so in this case it's not going to be too bad but trust me if you have higher resolution sims this is going to make this is going to be quite low quite slow and you see if i put it too far it's gonna kind of get even slower but now now we're getting sort of just bouncing through the um through the volume let me let's increase the smoke density and make it darker so we can get uh all right two one all right as you can see sort of bouncing through it a little bit and if i turn that off you see you don't have it no you do have it uh but it's it's quite slow and over here in this example it's not it's not too bad but trust me it's gonna get really slow really fast um another thing you can do is just keep this off and the pyrobate volume has this thing called scatter and this will do sort of a fake scattering and here this looks terrible but let's turn off masking all right so if masking is trying to do some masking thing which just doesn't look great but if we just do it like this you can see we get a good result uh it looks great much faster it's not as accurate but it's a lot faster to render again in this example with this low resolution pyro it's not necessarily you might not not necessarily think much of it but uh for my scenes it was literally changing some frames from being like 30 seconds of frame to being a couple of minutes of frame so there's quite a big difference so this scatter thing um is there and it will really help out uh whatever it is that you're doing uh we're gonna get into that in the main scene in a little bit because if you have multiple things inside of this object merge like let's say multiple like an extra piece of geometry coming in then this scatter's not gonna work so there's still ways to deal with that um but yeah that's the scatter thing and then we got nice looking scattering um yeah all right volume step rate is essentially how many slices is the is is the volume sort of cut up into like how many okay how many voxels is it gonna assemble um so if i if it's set to one it's gonna sample every voxel it's gonna make it a lot slower as you can see if it's at 2.25 it's gonna gonna sample um yeah well 25 percent of the uh of the total if you make this really low it's going to be fast but it's going to look terrible you can see now i'm not getting any detail but some some cases that might actually be fine you can see we really lose the detail if we go if we go really slow but if we make it really high like it's between one and like point five you're not really 25 you're not really losing much so generally 0.25 is pretty decent so uh some other things let's say if i want to just use the fire so let's say i want to render my fire separately like i have in um in new care where i have so i have fire and i have light on my objects separately which is generally what you want to want to want to do so you have some control and compositing so there's multiple ways to do this let me just show you a couple ways first let's just do our candle objects let's just put a grid and we just have the grid here now you might think because in mantra what you how you would do is you would make a it would make a volume light so how that would work is you would just make a volume light or we'll make a volume light as a geometry light and then select the thing and then put it in light well that doesn't work for for a karma what you would do is you would just put it into forced phantom so just put fire enforced phantom you can see now i get just the light and not the pyro the problem here is that let's say i want to increase the intensity of the light on the environment but i don't want to change the material because now what i would need to do in order to change the intensity i would need to and change the intensity here on my fire as well so let's say i would oh this is the scatter by the way uh on the fire so let's say i would like make this 500 so i get like brighter or 5000 like it would get brighter but if i now have a look at the fire as well if i just put fire in here uh let's turn it off in first phantom you can see now the look of that thing completely changed so that that and with the geo light uh the benefit there uh with mantra was that you could control those separately um you cannot really do in here yet so you would need you could do a couple ways to deal with this you could have a separate object and do like fire light or something and then hide that one and then keep keep like put fire in here and then turn that down again to like what was it like 67 or something let's make it 69 nicer number um and you could do forced phantom you could do the fire light and then here you could all right that's actually a problem with with this thing forced doesn't seem to work um on the camera so if i turn it on now it's gonna it's gonna it's gonna work uh but so you do need to turn it up but then you can see and i have it it's a little bit extreme here let me just put it to 500. uh as you can see so that that would work uh so it will it will be brighter um so there's one way you can you can do it and again i'm not sure why not forcing it because that's what it's supposed to be doing another way to do this is let me just remove this which i was doing in my project for the most part is let is just open up so enable anything of contents go in there go to lob network and what you can do here is a scene import i'm going to import the fire there we go so if i now go in here it's going to import this fire so we just have to separate fire now so now we're actually in lob context right i'm going to add a material library and i'll do a pyro material i mean let's just do a xpu pyro preview this is meant for xpu power which i didn't use and i'll get into that in a little bit um but you can just just have some simple controls so let's do something like that let's assign assign the thing so you can see we can do the intensity in here make it a lot brighter and then let's do geometry settings that's uh and we need to because these lob input primitives doesn't always work because especially for volumes because a volume is multiple primitives and for some reason this just doesn't always work and if you want to do it on everything just put a star and then it'll work again there's some some of these weird things but again what you want to do is you want to go to render visibility set or create i want to do phantom so similarly what you have before you can see now disappears what we want to then do is tree has light source yes so it's going to be treated as a light source so it's not going to be visible but it's going to be treated as a light source now let's merge it in here let's go all the way down and all right let's check this out let's turn off the fire there alright so you can see now this still works so we loaded it in and now we have separate controls here on the on the light and i can just put my fire back in here so now i have separate controls here on the the light material so i guess we could call this light material and you can just can control it sort of separately again they're still if we turn it off there's still light here because we actually also just put rendering the regular fire but again if we turn that off it would be completely disappeared so um yeah that's that's what i was doing with the duo light [Music] so some other stuff you can also use matte objects as let's let's just uh let's make a just a box to demo this i guess let's do a box all right there we go so if you just put something let's put it in between our fire right and then you can go on your grandma loop and force map then you can grab your box and need to go i had to restart with ini soda to network view with my trusty old linked to nine thing was gone all right let's like do nine all right there we go uh camera all right see now the box is matting out the thing if you want to do this in this level itself it's also pretty straightforward so let's turn off force map so how you do it in sliders itself you would do a scene import import my little box let's include invisible let's do another geometry settings settings there we go assign it and you go again to render visibility and then instead of doing the uh this one let's do oh yeah we don't need that one by the way we just need hold out mode setup create matte all right all right you can see there this works well we do by the way still need this thing because we need it to be uh invisible to primary raids as well so we do need whatever it is that was doing all right let's just primaries which one was it again um in i think oh yeah of course we still need to do i always keep forgetting that you need to put the star thing there and then let's turn this to do nothing all right there we go i always keep forgetting it it's just really annoying um but yeah you can see now this works and if you wanted to do some visibility that would also work so so you set up some matte objects because of course that's what we're going to be using for the uh for the trees so um you might ask why didn't i use karma xpu uh well there's a couple of problems with it let me go back to my original scene for example matte objects don't work let's try this one for example so let's say i go to i want to view this one let's just open up it open it up with the current viewport instead let's look through things yeah starting to get a little bit slower all right there we go all right so let's first put it to cpu by the way and let's press shift five by the way then you can actually check out this render view like this you see this works fine it gets matted out with the tree that's uh it's in there as well so there's uh there's there's rollout geometry let's see what happens if i put it to xpu so that's the with these holdouts i had before you see holdouts don't work so we will just we'll just render um these math objects here that i have it will just render them so uh that's why i didn't use xpu because i did really need these holdouts if you can get away with not using holdouts then uh you could use xpu but uh there was a problem here so there's with the xpu again that's why uh xpu is runs on gpu by the way there's there's a lot of issues still with it like i was trying this in my demo scene just now and for some reason not even working which is weird uh i'm not sure if i'm honest i'm not sure why because in my other scene it was working with xpu generally but um let's say i choose booed fire nine uh oh wait yeah out nine all right and it's now suddenly working not cpu engine yeah you can see for some reason it's not doing anything xp i'm not sure why but xp is still i don't necessarily recommend using it at this point there's still a lot of problems with it um but that that's why i didn't use it to still hold out weren't working so i did experiment with but um yeah that was that was one of the uh one of the important things there's a couple of other things we need to discuss about just karma and in general um but i think for the rest of the stuff let's just do it in my actual scene because like i've went over all of the sort of the like the basics um so let's now let's i guess jump back into the actual in the actual scene and let's start discussing how this was set up and the some of the issues that i that i ran into in order to in order to render this [Music] you

Channel: Tim van Helsdingen

Views: 11,333

Keywords: houdini, axiom, pyro, fire, fx, vfx, simulation, simulated, visual effects, sidefx, blender, learn houdini, fire simulation in houdini

Id: XiJ6xWcU70E

Length: 26min 30sec (1590 seconds)

Published: Wed Apr 06 2022