Intro to Houdini Tutorial 2.1 - The 23 Most Common Nodes

hi my name is David and today we're looking for 23 most used geometry nodes in Houdini and I think this is a great way to start learning Houdini because of the 8020 rule and these were some of the notes that you probably be using most of the time I found I got this idea from Mike Linden who I follow online and he's got great blog post about and how he came up with this so these are his twenty three most use nodes and actually if you scroll to the bottom of the page you can find a download that will help you find your most commonly used Houdini knows if you want to but I thought we'd just start off today by looking at some primitives so should be familiar with primitives from other programs today we're going to look at circle a tube lion sphere and grid Houdini primitives are similar to other 3d primitives but there are some differences in in them as well which is what we're going to take a look at soon so I'm gonna turn my background image off here and if I come up to the toolbar here and I can drag out a grid it's the viewport you see it's created a new grid object at the top level in my obj context you should be familiar with what I'm saying right now from my other Houdini tutorial where I talk about the interface and getting started so if you're not go watch that first cuz I'm gonna breathe breeze through some of the basic stuff so it's created a good object I don't want it to create a new geometry node at the top so I'm going to go back inside my tutorial mode go come up this option here and go create in context now if I control click on the tool again which creates it in the world 0 you'll see my grid object is in the same geometry node it's Thoreau mode which is nice and you'll see that we get some basic options in our parameter Spain every primitive has you know some of these options where we can move it off the center or change the scale stuff like that change your planners on change you know whether we only want rows columns triangles how just basically choosing how we're going to generate that geometry and one of the neat things about Houdini Prima's is the ability to change between NURBS Bezier points and I'll explain more what they do in a second and points you'll see that it's not actually generating any polygons just the points for the polygons which you can see if I visualize it there I'll show you what the option does if I create a circle node and give it safe for all right let's give five divisions and then I come up to the perimeter type and change it to nerves you'll see that it's actually a NURBS curve so it's interpolating smoothly between the points which is really cool and it's so neat to be able to just change the different primitive types on the fly for a like nearly any piece of geometry and it's also worth noting the difference between these two ones here primitive and polygon if you select primitive you'll see that there's actually there's no points that you can see well they're actually there is a point there if I middle click on my circle though you'll see this one point and that's because it's hiding it underneath here I just made my arm my point size a bit bigger you'll see it's there make it huge so it's hiding under my little nibble there but there is one point and so a primitive in Houdini is one point and the rest of the shape is generated mathematically around it sorry if you come to another primitive you also see what's there still sphere it starts off as a polygon mesh which means you know it's got all these faces and lines and stuff that you used to know if you change its parameters there's none of that but again metal clicking on the node there's one point and that is in the middle and then Houdini is generating the rest so it's important to note that there is only one point for primitives because that can have an impact on performance down the track because it doesn't need to carry all the weight of you know the information about every single point it's only the single point all right so a sphere is pretty easy there's actually not that much many options for a sphere a polygon busts a polygon mesh is main difference between them as the topology so probably gonna mesh you can you can choose different ways for it to generate actually that was pretty cool rows or it can generate triangles or quads and you'll see that at the top you get this funky-looking pole with where all the points are meeting at the top and you might not necessarily want that which is why a polygon might be useful if you put that if I penned a subdivision to that by tapping in subdivide and pressing shift enter which appends it and turns on the display flag you can see we can generate a bit of a smoother mesh with the polygon option as opposed to the blue girl mesh you see that doesn't look too pretty so yeah that's the main difference between those two options again for spheres you have nerves in Bezier polygon suit it's kind of similar to a primitive I'll have to explain that more later but basically a polygon soup is still representing that whole geometry as one point but the way it's doing that isn't it differently because you yeah we'll leave that for another another time again box is fairly similar except you also yet oh yeah it's it's basically the same there's not much more to cover on that let's have a quick look at the line the line is actually it's pretty useful you can change the length of it in the viewport by dragging this thing oh you know coming over here and doing the same thing again you can tell it to only generate points so it's not generating the line between the points and that's basically it those are the primitives there are a couple other types of primitives like a metal ball which I won't go into but that cool a platonic solid is also cool yeah here you got like a pyramid and if you change how many or if you change the type you can you know create a cube or octahedron or a teapot so if the tonic is also cool that's basically primitives it's got to make a little bit more spice down here by clicking on this down arrow and the timeline scared of that suit any deaths now so if ice like some points on my ice tree here by pressing two and just dragging a box around you'll see because I've got select only visible geometry turned on it only selects what's around this side whereas if I turn that off it will select all the geometry over there so if I leave that on flex and geometry and hit delete in a viewport you see this a big hole and in my network view it's appended a a blast node onto my sphere there's not a lot of options of the blast node you'll see it's got our our point selection there you can change its primitives or or edges or something like that but that won't necessarily be that useful to you because if you've used this specific point selection because there are different numbers obviously you can do you can change it to delete non-selective so it'll delete it will keep what you've selected which is the handy option five and a delete node you can also carry over the point selection through the delay node and you'll see it's exactly the same see what's the difference then the main difference between them is the delete is has a lot more offerings and also I found on the forums from a quick google search that the boss mode is much quicker for smaller operations like dealing you know something like this or only deleting a few points or a few primitives you'd you'd want to use the Blas node because it's just a cert back version of the light but the light node but for anything more complex you'll probably end up using the delete node so if I wanted to delete say every even primitive on my sphere I forgot the primitive numbers you see every second column has even numbers if I wanted to delete every second column you could put a simple expression in there at criminal modulo 2 equals zero so saying if there if there are even then we want to delete them of course have to change that to primitives and we've deleted every stinking cold you can delete by range is another handy one still have to get rid of my expression I think all right because that's what's actually the delete by range is doing so of course so it's selecting one of every two primitives it's just the same as Eric what our expression was doing so explaining every other primitive you can increase that to one of every four primitives now it's one of our six and splitting every sixth perm if you can sleep for of every six primitives and so on you'll have an option to keep the unused points the other another useful one is bounding box if I tell you have to turn off enable here on this tab get a bounding volume and we can say we want to delete everything inside of this bounding volume and if I move that up you'll see it's deleting only what's inside and as always you have the option for delete non selected so you can flip that around easily enough not the cool option is the the normal so I can say only you want to delete our facing polygons so if I bring out my Nobles here you'll see it's only deleting polygons with normals that are facing Joo North which is X Y Z so this is the Y parameter it's only deleting polygons within a 40 degree angle of that it's fine I get 0 it's not actually joining any because there's no stay polygons with the normal facing true up if I start increasing that slowly you see it's polluted the top cap yeah that's basically the the delete and if you stone sorry about the fuse that's the delete and the blast mode all right moving on next is the facet facets I think it would have odd one out in this group because it's I think the only pure modeling I mean all of them can be useful wallowing but it's the only traditional modeling operation here so let's have a quick look at that so the easiest way to think of a facet if you're coming from cinema 4d is to think of it as a form tag if I found a facet onto my box and took post compute normals it'll try and smooth out the corners of you know the harsh corners so it's kind of it controls your smoothing groups basically I didn't use it for much more than that although it does have other options you can explore on your own let's facet so next up we have attribute rename and now we're really moving into what I consider the heart of Houdini is attributes and groups and to explain this I'm gonna try a bit of an analogy so bear with me okay so if we think of our points and now primitives as the Lance little worker ants and there could be hundreds of them could be thousands we've got a whole colony of ants okay they all work really hard and the ants want to feed that Queen right there always carrying around bits of food they're always bringing stuff back to their nest and what they're carrying here on a strong little box could be anything it could be pieces of lettuce it could be a little worm I found that's kind of enough and now the analogous analogous to how attributes work in Hayden era these little paces could be anything that tells us about the app so we continue probably go of it see fire if we continue with the analogy this could carry information about the ants age who it's parents are what color it is how tall it is anything like that right so that's kind of how attributes were in Houdini so let's let's do an actual example we have that sphere and now trusty grid negroid I'm just going to tell it to generate I lay the points and now what I want to do is type in copy two points oops copy three points and I'm using this because we're gonna hit two birds one stone here copy is another commonly used node and so the first input of the copy is the primitive to copy so we want a copy house sphere to the target points of our grid then I'll display that and you can see we've got spheres copied onto the points of our grid I'll make you our spheres a little bit smaller now if I put the display flag just back onto my points for a second what if we wanted to color each of these points around and color how would we do that well we can do that with attributes which is like our little relax putting a little back onto our so putting a piece of lettuce into our ants back okay this is our first piece of lettuce I can name this color with the Australian spelling of course because I'm Australian or UK spelling I guess and I'm going to call this CD which is the global parameter for color Oh actually I should see how I got I get that as well by type in attribute ATT ATT bop put down something a pop court of watt which we'll also be looking at soon but I'm just going to show you how to find out these parameters okay so who did he comes with some global parameters that you can use all throughout Houdini and an easy way to remember what they are is to drop-down and attribute which are inside of now and look at these guys so you can see at the very top is our position position vector which is used all the time you've got our velocity this other common things here with good-ass CD which is again a vector and that's what controls our color so in my attribute crate I type in CD make it a point a point class is fine make it a vector and let's say we want to make them read so now I have to display that and might be hard to see so I'll see if I can pop the size of those points up scale point micro-sized well actually an easy way to show is just to highlight my couple points because the Kapital points will automatically take on the attributes of those of our little ants right of our points so now you can see they're all red now if I wanted to give them a random color I can go back to I have to recreate and type in a little expression will do R and now don't worry if this goes up a bit up your head I just want you to look at the visuals okay we'll be getting more into expressions and fancy stuff like that later on so now I'm just giving it a random value between zero and one based on its point number so every point has a unique point number which means every attribute here will be random so now we've given them the value from zero to one in the red Channel and that's being copied over because of our copy two points if I turn off copy point attributes you'll see it's no longer copying that over we do want that for now to quickly show off one of the other nodes that we had in our list is the attribute rename and let's say I want to rename my CD attribute to something else what else going use a scale see if that works P scale is another one of those global attributes strangely enough it's not in our little here so this one's a little bit harder the fun because it's to do it particles this is something that we'll look at later but P scale controls the size of each particle so now I'm still generating a vector with a random value of 0 to 1 in its first field actually I could even change this to a float because a so we rename this rename to be scale because the pay scale only needs a float it doesn't need a vector I cared at these as well if I want from the attribute name because we're only doing one just like the simplest rename we're only doing one point P damn and because that copy two points is copying over all those attributes it's copying the P scale from the grid points to a spheres and now we had very varying sizes of spheres diagnosing that here in Houdini and that's what the geometry spreadsheet I should explain what I'm doing there should know so I opened up the geometry show tree which I actually mentioned in the first tutorial you might remember and I got to this area the top right corner and go split pane top and bottom or old right bracket and that'll split give me a new pane down the bottom for my geometry spreadsheet this is how I organize it I like having this guy down here and how use this guy is you're not always going to be looking at you know every single one of these values and in fact you basically never do that you but you usually check the minimum that maximum values of any attribute and you can do that by toggling the sort function it's like any other spreadsheet sort of like Excel spreadsheet where you can sort by different values so we could sort it by our minimum color value which is point zero one which of course is getting transferred to the P scale so the very smallest guys that we'll see will have a pay scale of 0.01 which might be this guy over here we could we could tell effect if we turn on our point numbers well it's a lot of points maybe we look for a point 95 which is down here so this guy here yeah so he's decimals got point 95 he's the smallest ant so to speak now going back to our ants analogy that that piece scale that color or that piece of lettuce that could be absolutely anything about that point right that's one of the great things about attributes is you can create your own you name them whatever you want you can give them whatever values you want and you can use them to drive anything you want now this little expression is great there's actually an easier way to create random valleys and that's with especially on attributes that's with attribute randomized third I probably should have shown you this straighter straightaway actually because it's a little bit more intuitive rather than looking up some expressions when you're being up we're bringing in our CD s route let's go three dimensions and we want our minimum value of the red channel which is the first one to be zero and we're going to put the others at one so there's no randomization happening that one so let's able the the pay scale note as well of course I have to delete my expression just make that zero for default and you'll still you'll see that in the attribute spreadsheet we're initially creating all of the color to black you can't really see it there but then we're randomizing it to red and copying it two points finally we can actually do the same thing all in all in one node which is the lovely attribute wrangle so we've got our friend the attribute wrangle here and by default this is running over our points which is what we want so for every single point in our grid it's going to form this code now we can do the same thing that we did before and now have to recreate by creating a CV attribute and making it equal to a vector which we define the securely brackets and make that one zero zero and the Kelly bracket see it's airing out there because I hit ctrl enter and it hasn't finished and then we finished off with a semicolon that one while you're inside of the attribute wrangle you can press ctrl n Tartu to accept it or you can just click outside of the note it's the easiest bit of code ever right all we're doing is creating our global CD attribute which is that call attribute and setting its first value to one now that's getting copied over to our points so well best fears are becoming automatically read however if I wanted to randomize it there's something I have to do a little bit differently here and that's to do with I'm not getting too complex for first effects lesson but just hang in there for this section to do I couldn't just do a randomized function inside of it let's just try it okay we'll do a round and again we'll base it on our point number PT num control enter and that's going to air out that's the way because of we're initializing our vector so initializing means just the way we're setting it up and to fix that there is another function we can use called set so we're sitting the initial values of our vector and the first one the first value is a random number based on point number just like we did before I'm going to read rename our node create color and randomize you always want to try and give your nodes meaningful names if you can load things like sphere and grid I'm not sure I would ever rename those I'll just leave them like they are so in this in this one line of code we're doing what these two nodes we're doing before yeah now as a beginner this might might not make as much sense to you as what these two nodes are doing which is why I recommend you use these nodes if you can actually because there are a little bit more intuitive than writing functions which you have no idea where they come from or what they are but what one thing I did want to just quickly show you here is if you're feeling a little bit confident and a little bit up to it and you do happen to create an error with your function you don't know why it's okay what you can do is click over the blue part the beginning funk the beginning part of the function press f1 and that'll bring up the help for it so you can find out what it's expecting you know what it does and exactly what values expecting okay the help is really useful I encourage you to use it all the time I'm using it everyday basically and you become pretty reliant on it just like Google another way you can bring up the help is by clicking up and clicking on this question mark and any node that'll bring up the help for this specific node and then you can type in and and you'll see the first option will be the random X function there are there are other random functions as well I just thought I would show you this while we're doing it there is a random vex function which i think is the preferred function because it can can do fancy stuff but for this example it doesn't really matter that's the basics of the ass root wrangle and attributes in general another thing the market is you when you're starting out and you're you're seeing all these you know point and rango primitive wrangle detail or angle they will actually have different names in the in the tab menu so that confused me when I started so if you type in Rango alright there's like seven different round goals and I can be a little bit confusing but I want you to understand that these all do the same thing except if I top and wrangle again and I say grab a prudent wrangle the only thing that's different is it's like the permit hearing that first you know what's running over so keep that in mind they all do the same and the same thing is with the box right if I type in Bob there's a ton of different box that come up but actually a bunch of these you can change between them so you choose the different the different time of whap so they all kind of do the same thing strangely enough except the volume pop the volume pop is its own separate little guy you'll see there's no there's no option to change the type of thing you're iterating over in the volume bop but we'll leave that for now okay I think that's enough for the basics of attributes attributes are super powerful and it really is the the core of how Houdini works your aunts are always carrying little little packets of something to their Queen right and that is how the colony survives okay because they're always carrying around stuff and it can be absolutely anything I hope I didn't lose you in that analogy and we're going to continue on with the next node so we've had a quick look at the attribute rename the vault and this is why is add the copy cuz we also take that one off after it Wrangell that's recreate yes should we what we didn't quite look into too much yet I will cover that a bit more and second we did look at it as a way of remembering those global parameters so that's a very handy trick that I want you to remember again so next up we have the ulema k-- and also because it's similar we'll do the file so let's have a quick look at them the the file node you actually would have noticed that the start of the lesson you know hide this again if i create any any

Channel: David Uebergang

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Keywords: motion graphics, mograph, houdini, intro, introduction, beginner, david uebergang, tutorial, newb, houdini tutorial, beginner houdini, houdini sops, common geometry nodes houdini

Id: TWJvCOweGvY

Length: 32min 0sec (1920 seconds)

Published: Wed May 02 2018