hi guys and welcome to yet another devcast. Today, it will be a Houdini Unity devcast, and it will be about the vertex animation toolset. I will be continuing from my earlier devcast where I showed you the Houdini engine implementation in Unity and how to work with it, where I basically destroyed a structure and generated an asset in editor time to be used in pretty much any of your game. One of the questions I got on that video and on Reddit was if it's possible to export destruction animation from Houdini into Unity using these tools. It's not possible in a straightforward way using the Houdini engine. You can catch the meshes and so on, but there is another way to export animations from Houdini into Unity in a very performant way. It is the vertex animation toolset, where you will basically bake, or Houdini will bake this animation into textures. So, there are multiple ways to do it, or multiple types of vertex

animations for various utilizations. We are going to look at rigid body dynamics and exporting these textures for this specific packed geometry because all of these exporters have different traders basically and different data that they store. For example, for clothes, there will be different data to store for cloth type animations, and different will be for these rigid body data. But most of the approach is how to do that and how to work with the Diabetics animation toolset will be the same. So, if you want to later export the different type of vertex animation, you can feel free to do so. So, as I said, I will start with my previous where I would end it, you know, my previous video. But I will not use the building that I destroyed in a previous video because, firstly, I don't have the project. So, I created this project from scratch. And secondly, it was, as I mentioned in the video, it was not a good geometry for destruction. So, to avoid all

these things with open Geometry and so on, so I made it more simpler by using this Geo, which is a pillar from a cemetery asset pack from BD game. So if you don't know how to set up Houdini engine and how to sync it with Houdini with Unity, feel free to watch the previous video. So I already set up that it's connected, so any geometry that I have here and set up as an input for this asset for Houdini engine asset, it will show in Houdini. So that's what I said because you can use the vertex animation tool set without Unity. It doesn't really need to go. The geometry doesn't need to come from Unity, but to have this round to rip set up, it's way better because you are working with the geometry that's already in Unity, and you are sending it to Houdini where you will back and bake the animation to textures and send them back to Unity so you can

you can feel free to load this fbx directly into Houdini and work like that, but I like to have this round trip pipeline where I just basically have this scene. Okay, I don't want to work with this single asset, and I want to break it and export the animations. I can send it to Houdini this way instead of going and starting my own session of Houdini and going from FBX and so on. So, this way, I can also set up if I change this geometry here. I can go right away and make different animations for different geometries with a single setup instead of having to open the session between the different effects and so on. But feel free to work as you see fit. You can work the part with the vertex animation tool set in any way, without Unity or with Unity. You can also use other legends as well. So, this is the basic setup for Unity. I have a Houdini engine set up. I have the single Houdini asset with a single slot.

which is a Unity measure, and I'm sending that mesh. There is no material at the moment; I will finish that at a later stage. So now here we have this setup, which was created by Unity, by the Houdini engine from Unity, and with this Geo note, which I created to destroy this pillar. These geometry nodes, I went over them in previous tutorials, so if you are not sure, you can just check it out. It's basically the Geo asset with these slots. There is a single input, which is here, and merging then all the inputs together, and so on. So what I want to access is basically this one, which is merged all the inputs for my use case. There is a single input, so anyway, but which merge all the inputs from the Unity Houdini engine asset, and I can take it into my jio. So let's go over this simple setup I prepared here. This is the merge, which is referencing the node that comes from

Unity. Uh, what I'm going to do here is I'm going to delete the uv2 because if I go and check the spreadsheet for this, I can see that on this one, oh, this actually doesn't have uv2 attributes, but most of the meshes I tried it with, I had uv2 at the attribute on their vertices, which is not something that the vertex animation toolset supports. So, it will basically use it for a different thing, and it will tell you that you cannot have, I will give you a warning that you should not have a uv2 set on your geometry. So, that's what I, why I am downloading them, deleting them here. As you can see, this pillar, since I changed the geometry, I tried this tool set on various geometries, doesn't have this. So, this attribute is, this node is obsolete for the setup, but I will left it here because if I change the geometry later and there will be a geo with more UV sets, I need to get rid of it, so.

that's why I'm deleting this attribute. The next note is uh maybe something that's new because if you watched my other tutorials from Houdini. I used the voronoi fracture with the scatter and so on to destroy the building. So here I chose uh different uh different way. As I mentioned in the previous video, there are like tons, so like thousands of ways how to destroy things in Houdini. That's what I like about it. So uh here in this setup, I'm using the RBD method material fracture note, which is basically multiple nodes together with the foreign and so on. So I specified that I want the concrete material. You can get glass, wood, and so on. And I just have a single fracture level uh. And then here is the setup for the fracture ratio for the scatter points. As I mentioned, it's very, very similar to to having that as a separate note, but I like this note because it's put all together and you can get uh good results with a single note uh, especially

for low poly assets like this. So, I'm breaking it up now. Here, I'm assembling the pieces. You need to have this because if I go here and compare it to this, you can see that now I have these pieces together, and there is a new attribute for each piece compared to this one because this is what the vertex animation tool set for rigid body dynamics will need. It will need this attribute, and it will need to have all these geometries, geometry pieces together because it will generate the pivots and the offsets of the animation based on all these pieces. Because the vertex is animated based on each separate body or each separate piece, that's why it is a specific vertex animation for rigid body dynamics. So, I'm using the assemble node to assemble these together, to these pieces here. I am grouping it up. You can see I'm using this volume, this bounding sphere volume, and I'm

creating an activate group. So, let me show you what it does. It basically sets all these points, all these pieces inside this group to be part of the group activate. And then I'm using it here as a space node for, because I'm not going to use additional velocity. I played with it a bit, but I'm going to use gravity only. So, here I am using this activate group to set an active attribute on these pieces. As you can see, based on the activate group, I'm setting this active attribute. And I'm going to use this active attribute inside the RBD bullet solver, which is basically the thing that does our simulation. So, I need to go here just to see the simulation. It's a very simple simulation, easy to calculate. I'm not using any caching. You should cache if you have any complicated simulation. And here is a basic, very basic setup with a ground plane as a collision, because otherwise, it wouldn't collide with anything. You have this plane here, as I mentioned in

the previous video as well. You have displayed here, but we are not importing this plane into Houdini. So, I need some collision geometry, and this solver can have this very simple active ground play to simulate the basic stuff without having explicit geometry for the ground plane. And I, as I said, I'm using just the gravity as a force. I'm not using any other velocity. You can add a velocity if you want some kind of explosion, and so on. And there is some more stuff. So, this solver automatically uses the activate your active property attribute to only active and simulate the stuff that has this attribute as true. And anything else that I changed here is the output because, by default, it doesn't output this or transfer these attributes. And the vertex animation tools need these two attributes to basically export them into the textures because, as I mentioned, the textures or the textures, the animation textures for especially for the rigid body dynamics, are using the pieces and pivots and offsets of the pieces instead of each particular

vertex to put it simply so. And what I'm doing here is a null node, as I mentioned in all our Houdini videos. All my Houdini videos, I'm always using a null node with an out name. It's an industry standard, as far as I can see it. So, so I can reference to this because if I wanted to add any kind of like posts, post notes after the solver and so on, and I reference this solver as my out note in my other networks, I would need to always go into the other network and change the change the reference to this last node. So my last note is always a null node with the out, and I can inject any kind of functional nodes between the previous and the last node. Okay, so we have this Geo working. As we can see, the simulation is working perfectly. I will disable this just to see the simulation in my out note. Okay, and I can go to out because here

In the outputs, we can set up the vertex animation textures. It's pretty easy to set up. You need to have the Side Effects Labs installed. It's not something that is by default installed with Houdini, but you can download it, or you can even, you will have only this update tool set if you don't have it installed by the default installation of UD only. You will have the update tool set button, and you can go there and update it from the Houdini launcher and so on. There are multiple ways to install it, as always with Houdini. I think this is one of the weak points of Houdini, how you install stuff into it. And it's not just these Side Effects Labs or external renderers. It's always a pain. You are changing environment variables, or you are using some JSON packages, and so on, and so on. It changes, but there is no straightforward way to it, to install stuff at the moment. Okay, they did a lot of work now with the Houdini installer, but still, it's...

it's a pain compared to other more streamlined software. Very, very, very easy to install plugins, not so in Houdini. But, as I said, you can just click to update the tool set, and it's very easy to install. I'm using it because I have a Houdini engine. I bought it on Steam. There is a kind of like difference between having either installed from Steam and having the default installation. So, for example, the Houdini launcher, Houdini installer doesn't really work with the Houdini Steam version at the dead. Well, it cannot find the installation and so on. It's a bit of a pain, but there is a ton of how-to guides on the internet how to install the side effects Labs. So, feel free. I'm not going to go over that. It's just a topic. It can be a lengthy topic that I'm not going to cover. And if once you have it installed, you see this as bat, which is vertex animation textures or vertex animation tool sets. The same abbreviation.

so we I added it to the outputs and uh is a single node so I can just select it. I don't really need to go into it. I was just uh trying to get this one. So what are we going to set up here first? We want, as I said, rigid body dynamics. There are other simulations or stuff that you can export as vertex animations from Houdini, and it's you you can use this same note uh, and it will export different attributes in a different way for uh, for example, the soft demo of animations per vertex. This is using the pipe pivots and PCs, as I mentioned. The dynamic ramaching is used for for a variable uh, type of outputs where the number of vertices is changing in time, which for example, fluid simulations. So, so you don't have the same number of vertices, which is a lot of the time crucial in in vertex animations uh, because you you prepare the vertices or the textures in a way, for example, you have the same number, the number of color.

columns which reflect the number of vertices, but in the dynamic ramishing, you can change the vertices, so you need to have some kind of space and so on. And then finally, this is the only one that I didn't play with, which is the particle Sprites, where you can simulate particle systems as in using vertex animation. So we are going to use the rigid body Dynamics, and we are going to use Unity here. We are setting up the time; it's basically referencing my setup here. So if I change it in my timeline, it will automatically change here. This is the input here, the null node I just mentioned, which I have in my fracture as out. So if I add or remove some notes from the Geo Network, the null node will always stay the same, and it will always be referenced by this. And here you can pretty much leave this to the default settings. I'm using EXR, but you can use PNG and other formats. I'm using HDR. This is the thing that will affect how you import.

the textures into Unity, but Houdini made a part of their Unity package preset for importing this type of textures. So, you can just apply the preset, and you can see how my last exercise was so. This is a bit of a bit of a stretch too much, but it doesn't matter. It will use up to this number, not this number of this size, so I will leave it like that. And here is the input. You can see what it requires. If I didn't have some part of the attributes, you will see a warning sign here. For example, if I didn't have the pivot or I didn't have the pieces or something like that, it will tell you in a warning sign that what was missing. And you can also see the stuff I mentioned that you cannot have the uv2, uv3, and uv4 attributes because it's used, so you shouldn't include them into your Geo. That's why I created the delete attribute stuff. Okay, this is pretty much all you need.

and this is the export. So, what we are going to export. So, this is the export path. So, this is the hip export. This is basically where you opened this file. So, it will export into this path. And that's where you can export directly into Unity. So, it will automatically override your Unity stuff. And what was the name of the asset. Some kind of suffix. And this is what it should be included. This affects the shaders as well. So, by default, it's geoposition, rotation, and colors. I don't really want colors because I'm not changing colors in this simulation. I don't need it. I will use the texture that was originally on the asset, which is not directly supported by the shaders, but I will change it. I will show you. So, I just need the Geo, the position, and rotation. So, it will export the FBX geometry for the simulation, position texture, animation texture, and rotation animation texture. And this is the Unity material. Or I will leave it to the default settings. Advanced didn't change anything.

Target engine, which is Unity, it's automatically set to that. And here you can get the shaders, so you can select the engine you want, and you can click this button, and it will open a URL where you can get the Unity package and the guides for the shaders for the vertex animation textures, which we will use in Unity. I already have it installed, so you need it to get vertex animations working inside Unity. So we have everything set up, we can just render it. So we will click, if I click render all, it will render all the simulation that I have into this texture. So it's basically on the background, it will go over the simulation, render all these 100 frames into these textures. And since I have it exported in Unity, this is what it exported. We have the Geo, which is basically the broken geometry. It's not the geometry you imported, it's a different geometry with all the broken pieces that will be animated by the textures. I already have it applied or

correctly imported. But if you import it for the first time, if it just gets exported from the Houdini, I want to get it into Unity. You can use the pressure Dimension. This is what will be installed with the unity package in the vertex animation tool set I just show you. So, you just click the pressure and then click apply. I already have it applied, so that's why nothing changed. You need to do the same thing for the textures. They have two presses here. One is for the all the year and one is for the HDR. So, since I am using HDR textures, I use this preset. You don't need to do anything for this material. I will get back to it later. So, this is the two textures. As you can see, we can just make it bigger. Maybe it doesn't Zoom. Anyway, this is for the positions. So, you have all these. I think it's like 30 columns with 100 frames. So, this is the piece. As you can see, as I mentioned in the spreadsheet, we

have 30 pieces. So, this type of vehicle text animation is animating the pieces. It's not really per vertex; all the vertices that are specific for that piece will use the same animation data with the orientation and pivot of the piece. So, if you want a more technical explanation, because you can just play it and you will see, but what I'm mentioning here a bit because it is very specific for this kind of vertex animation, because it's not vertex animation which is unique per vertex, but all the vertices in a single piece will use a single column from this texture with the Orient and offset data. So, that's why we have this small texture, even though there is a lot of actual vertices there. Not every vertex has its own column, same for the rotation. So, if you want to work on your own vertex animations, this is something that you can actually take into account and work with. If you just have a specific like stuff animating, you can specify all these vertices and animate.

them in a single row or column in the texture. It's a very nice way to optimize vertex animations. So, I will go here and take our Geo into the scene. Nothing is happening, uh, because, uh, because I don't have the material setup. I will lock this one and assign the material. I already assigned these textures, so you can see it's working. But by default, you will need to assign this position texture into the position, position, not position texture two, and into the rotation. If you also exported color texture, you will need, obviously, to assign it to the color, but I'm not working with colors in my simulation, so there is no need for that. And if you enable the auto playback, you will see that it is automatically animating. Now, as I mentioned, I want the original texture from the beat, the game asset, to show. If I assign it here, it will not really work. I can do that. I think it's this one. Oh, it's working because I changed again. I changed the default default.

asset so by default there are. They are using a custom interpolator for color. So this was the default offset. So this is how it will look for you if you just use the original Houdini material, and it's not really something that you want. So I went into the Shader, and I didn't really clean it up. I just didn't want to use the custom interpolator that they just referenced here, and then use this to the fragment, to the base color. I just added the additional sample texture note with the same parameters. So I'm using their parameter in the shade graph, and just assign it to the UV set, UV0 set, which we left untouched in our fracture here. I just deleted the UV2 and so on. So this is the original UV set, which stayed untouched. So I'm using it to map this color texture and assign it into the color output in the fragment Shader. So I can

now see the original color on my asset, and I can animate it. No problem. There are some new UV sets happening, obviously, because there were no UVs for the internal pieces. But since Bit Game is using this colorized type of textures, it works well in this case, because even the inside with the custom UVs that got generated looks like it's from there. But as I mentioned in my previous video, where was I destroying the building, it's not always the case. So, that's how I mentioned how you can assign a specific texture or a specific UV set for internal parts of the broke-down geometry. You can check out my previous video. So, this is how you can use the new vertex texture, vertex animation textures, or vertex animation tools from Houdini inside Unity, and using this round trip from basically sending any geometry into Houdini, generating the stuff you need, and getting it back. If there are any questions, feel free to ask, and I hope you enjoyed it. Thank you.

Unity/Houdini Devcast - Vertex Animation Textures

Unity/Houdini Devcast - Vertex Animation Textures

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