Sidefx Houdini Basics

We continue our look at the core digital content creation applications; this issue, we explore Sidefx Houdini

We continue our look at the core digital content creation apps

If you are new to CGI, there are far too many tools to choose from in a dizzying array of software. This series aims to break everything in CGI down to the very basics so that every artist can be armed with the knowledge of which tool is best. This month we look at Houdini.

When experienced CGI artists are asked what 3D application can do everything, many will answer with Houdini. Still, they will likely argue that it is also the most intimidating 3D application due to its distinctive and sophisticated ‘node’-based approach to asset and scene creation.

Sidefx, the developers of Houdini, have realised that this complexity is also the reason that it is one of the most loved applications in CG creation. They have strived and have succeeded in making Houdini one of the most accessible pieces of software in the CG industry.

Houdini is embedded deeply within the VFX and game community as the FX problem solver of choice for fluid dynamics, destruction, complex motion graphics and character work

Houdini utilises a nodebased workflow, which can be a culture shock for new artists. Still, when it is mastered, or at least understood, it means that every component in a scene is easily manipulatable.

The other attraction of Houdini is the way that it can handle this data. Houdini is far faster at working with dense motion graphics scenes for example than other software. The great thing about Houdini’s node-based workflow is that if there are changes, they are easier to manage and implement than would be possible in other software, making Houdini a great sandbox for experimentation.

The Academy Award-winning Sidefx are constantly working with other leaders in the CG community to continually add new cutting-edge resources. With Houdini 18 this includes the new Sidefx Solaris layout workflow, which is based on the open-source Universal Scene Description (USD) format developed by Pixar that has the potential to revolutionise artist workflows, from freelancers to major VFX studios.

With a compelling price structure, every CG artist deserves to have a copy of Houdini on their machine. Let’s take a quick look at modelling and rendering in Houdini, as well as using Solaris.

01 MODEL IN HOUDINI

Artist Rohan Dalvi has created this box of cupcakes to show off some of the key elements of Houdini 18. The cake geometry is created using a variety of poly modelling tools that each result in nodes wired together into a procedural network. This network defines the flow of data and updates can be easily made on any of the nodes to tweak the final look. VDB volume tools are then used to bring together the parts into a single coherent cake surface.

It is then possible to use the network to branch off and build the paper wrapping utilising the shape of the cupcake as a guide.

02 DETAILS AND VARIATIONS

The icing is created by sweeping geometry along a spiral, then using volumes to again create a coherent shape. This approach can be used to add different kinds of toppings with a dedicated copy to points node, which makes it easy to get variation in the layout of the pieces. It is possible to create a variety of different cupcake designs that all spring from the same base shape. This network can be converted into a single node called a Houdini Digital Asset, then that is turned into a cupcake generator with top-level parameters to control the results.

03 USE SOLARIS

The cupcake models are then brought into Solaris, which is a different kind of node network in Houdini dedicated to lookdev, layout and lighting. Here everything becomes part of a USD Scene Graph and can be used to prepare the model for layout.

Randomisation can be added to make the cupcakes look less uniform. This involves the use of USD instancing combined with the control provided by the Houdini networks. One benefit of working in Solaris is that you have a dedicated layout and lighting environment backed up by the full proceduralism of Houdini.

04 RENDERING

Once the layout is all set up, lights and cameras are added and can be manipulated using interactive artist-friendly tools, and then everything is available to render using Karma. Karma is a Hydra-compatible renderer, which means that it renders USD directly. Karma is currently in beta and is available as part of Houdini. Other Hydra-compatible renderers include Renderman 23, Arnold, Redshift and Prorender, which can all be used with the freelancer-friendly Houdini Indie edition, which is available on Steam as well as directly from Sidefx. •