Creating Procedural Generators in Houdini

Introduction

Hi everyone, my name is Radu Cius, I'm from Chisinau, Moldova. My journey into the CG world started in 2012 when I was studying 3D, a few years later I got a job as a 3D Artist at Riift Studio and then moved on to the position of Lead Environment Artist. I am currently working as a Level Artist/Houdini R&D at Big Medium Small.

Houdini

At one point, I started studying Houdini and applying it simultaneously to various tasks in studio projects. Gradually, I started working only in Houdini on simulations, procedurally generated props, and sometimes procedurally generated animations. One of the reasons I started studying Houdini was the flexibility and speed in creating various iterations within the project.

With each update for Houdini, the procedural generation techniques become more optimized and more efficient due to the new tools that appear. In my opinion, one of the best improvements was the release of the KineFX tool, which provides a procedural approach to producing and manipulating character motion. I also use SideFX Labs very often in game development.

The "fear of Houdini" phenomenon is found among artists possibly because it is fueled by some wrong statements, for example, that to become a good specialist in Houdini, you have to know programming and mathematics very well, which is a wrong opinion. Houdini isn't scary. It is incredible software that has an easy-to-understand interface for beginners and is intuitive for those migrating from other 3D software.  

Creating a Generator

The process of creating a new generator consists of 2 parts. In the escalator project, for example, the main task was to be able to change the height, width, and length of the escalator from the interface and to automatically generate the animation of the steps. 

1. References, Documentation, Sketches.

I start to look for image references; for the Procedural Escalator project, I also needed to find documentation to understand how it works, the component parts of which it is composed, and their correct name from a technical point of view. After that, I created some sketches where I added cyberpunk elements.  

2. Procedural modeling in Houdini.

The procedural method always practically implies a simple basis with which the whole process begins. In my case, the escalator is generated from a cube, of course, I could also start from a point (vertex) or a line, but the optimal thing was to start with a cube. This form is the basis of the entire project, the branching begins from here with the networks of nodes that make up the elements of the generator. 

I also created a vertex mask that I use in Unreal Engine 4 materials. 

After generating the escalator, I can also animate the stairs, the animation is automatically generated and exported depending on the length of the escalator. 

As I progress in the project, the networks of nodes become more complex and I use tools created especially for this project, for example, the cable generator that is integrated into the escalator. 

Towards the end, I generate UVs and assign the materials from Unreal Engine 4.

The main challenges behind such generators appear if they become complex, then UVs generation starts to become a more interesting task that requires time and research. The task becomes more complex because the mesh changes its size and shape after each generation, for this reason, procedural methods of UVs generation are needed that take all these changes into account. 

I think that Houdini will be used more in the future because currently, the trend is changing, VFX and game studios are starting to use Houdini as the main software in the pipeline, and it is used in several production departments such as environments, FX, SFX, crowds, and assets. 

Houdini Resources

The best way to start Houdini is to go to the SideFX website, there are guides and a learning path for beginners. For a good and effective start, become as familiar as possible with Houdini, study the basics such as Houdini workspace, radial menus, shelf tools, etc. Use the SideFX documentation. Houdini is one of the best-documented software, each node is described in great detail and with examples for some nodes. 

Here are some online resources for beginners: 

Forums: 

• SideFX
• od|force

Documentation and project file/quick examples:

• SideFX
• cgwiki

Here is an impressive list of Houdini resources, free tutorials, forums, etc.

Radu Cius, Environment Artist

Interview conducted by Arti Burton