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Houdini 8 Review: New Dynamic Simulation Environment

Barbara Robertson flies to Genzano, Italy, for the I Castelli Animati festival and says bravo to what she found there.

The recently released Houdini version 8 arguably delivers the best dynamic simulation environment on the market, as well as further improvements to lighting and character tools. All images © Side Effects Software.

Houdini, from Toronto-based Side Effects Software (sidefx.com), has always attracted certain sectors of the high-end 3D animation industry. Lighting, shading and animation improvements in recent versions have only increased its stature among leading industry professionals. The recently released Houdini version 8 arguably delivers the best dynamic simulation environment on the market, as well as further improvements to lighting and character tools. For those who are unfamiliar with developments in recent versions of Houdini, its time to take a closer look at this software.

Coming Up on the Outside

Houdini is a bit of a dark horse among 3D animation packages. Throughout its 20-year history, Side Effects have traditionally avoided the volume of aggressive and misleading marketing statements characteristic of its competitors. Many wouldnt know, for instance, that Houdini was the first 3D animation software to be honored with an Academy Award, or that it was the first package to have a built-in compositor, non-linear animation tools and built-in comprehensive RenderMan support.

Despite this, Houdini has long enjoyed widespread use among many of the worlds largest effects houses, and is responsible for many of the most dramatic visual effects made year after year (including last years Stealth). Following improvements to lighting and animation workflow in recent versions, a number of feature animation studios have started to use Houdini as their primary tool. Two of the animated features due for theatrical release in 2006 were created using Houdini (including Disneys The Wild created by C.O.R.E. Feature Animation).

Lighting, shading and animation improvements in recent versions have only increased its stature among leading industry professionals.

Fully Procedural

For those new to Houdini, its distinguishing characteristic is that it is fully procedural. Houdini has a node-based interface similar to that of many popular compositing and crowd AI packages. This type of proceduralism gives users the ability to go back and change any step in the production workflow at any point, and then have those changes flow through the entire network. Its kind of like a scripting language with a node based GUI.

Among other things, this kind of proceduralism permits artists to respond quickly to dramatic changes in creative direction. When confronted with such directorial decisions, Houdini users are more likely to smile and say, sure not a problem than die a hundred deaths at the prospect of having to redo two days worth of work because they can no longer undo some step they took back then.

It has been noted that Houdinis procedural architecture is also part of the reason why it isnt full of bugs, and new features can be added to new iterations without introducing new bugs.

Large Pipeline Throughput + Highly Recyclable Code

Besides creating a very manageable construction history, proceduralism enables users to create scene files that are easily re-usable on multiple shots. Once properly set up, new input data can be plugged into the head of a procedure, and the final product comes out the other end with minimal additional user time.

In Houdini version 7, a digital asset creation and management system was introduced to facilitate the kind of code re-use common among Houdini users. Houdini Digital Assets basically permit the creation of easy-to-use interfaces to complex procedures that are encapsulated below the interface in sub-networks. Things such as character rigs, common effects, or even just regularly used tools for massaging vectors can be bundled up in a single node, with all complexity hidden behind an artist friendly interface. With these digital assets saved to disk they can then be installed in multiple scene files either by hand or by using a few lines of script. Later, the technical director responsible for managing the digital asset can make an improvement to a rig encapsulated by a digital asset, save the change, and every scene file with that digital asset installed will automatically update.

This kind of code re-usability makes it easy to automate the production of 3D elements for multiple shots across multiple sequences. For effects needed in multiple shots, solo technical directors can use a few lines of Houdinis native script language to create or modify multiple scene files so as to complete new versions of an element for every shot in a sequence. A possible part of this scenario could be that Houdini uses its excellent unix shell, python, perl, java or xml tools to interface with some external database so as to read in all the unique production data for that shot. This data can be used to select and install the necessary digital assets for that shot, arm them with particular parameter settings from the database and then execute their output. It might take two minutes to launch hundreds of elements. If revisions are necessary, the easy-to-use interfaces possible with digital assets permit entry-level artists to make necessary changes on a shot-by-shot basis.

Houdini's distinguishing characteristic is that it is fully procedural. It gives users the ability to go back and change any step in the production workflow at any point, and then have those changes flow through the entire network.

VFX

Since the mid-1980s Side Effects Software have created 3D tools with arguably the best particle generation tools on the market. This has helped Houdini carve out a solid niche among houses specializing in difficult visual effects work. With the release of a new dynamic simulation environment in version 8, Houdini strengthens its claim to pre-eminence among effects creation software. The dynamic simulation tool-set now available in version 8 comes standard with wire, cloth and rigid body solvers, as well as a large set of operators for creating and controlling simulation data. These include special solvers permitting both particle and procedural modeling procedures to interact with simulations both during and after actual simulation. (While fluid solvers are expected in future versions of Houdini, interfaces to third party fluid simulation software packages are currently available.)

While each of the existing rigid body, cloth and wire solvers are useful on their own, the new dynamics environment is novel in that simulations can draw on multiple solvers, and Houdinis entire suite of procedural modeling and animation tools during a simulation. For example, it is possible to collide rigid bodies with cloth objects and have both respond. It is also possible to collide rigid bodies with the branches of a tree controlled by a wire solver, and have both respond. It is additionally possible to bring a particle animation into a simulation, and have it interact with a simulation. And it is also possible to have rigid body collisions continuously remodel objects during a simulation.

With the release of a new dynamic simulation environment in version 8, Houdini strengthens its claim to pre-eminence among effects creation software.

Rigid Bodies

The new rigid body dynamics tools specifically are among the fastest, most accurate, flexible and stable on the market. Here are some of the features of these tools:

  • Simulations can be easily optimized for any number of objects and any degree of accuracy.

  • Objects can be constrained in multiple axes so that keyframe animation can be combined with rigid body animation.

  • Models of any weight, shape and complexity can be used without adversely effecting simulation times.

  • The breaking apart of pre-fractured/glued object can be either automatic based on impacts, or choreographed based on keyframing or other features/events in the simulation.

  • The ability to solve rigid body simulations involving deforming geometry.

  • The ability to interact with other solvers such as cloth, particle or wire simulations.

  • The ability to control a simulation in a procedural way based onexpressions and information from the simulation.

  • The integration with the rest of Houdini allows rigid body results to be applied procedurally to control other parts of an animation.

  • Stand-alone rigid body dynamics tools of comparable ability cost far more than a license of Houdini, and come without all the other tools that Houdini offers.

A Strong Future

The addition of the dynamic simulation environment following further improvements in the area of lighting and animation make this new version of Houdini deserving of serious attention. If you are a business owner, you need to maximize the return on your most expensive overhead your human resources. If you are an animator, you need to see that high-end computer graphics production is all about engineering beautiful imagery using the most productive systems available. With the arrival of version 8, Houdini offers an incomparable combination of functionality and efficiency. Looking down the track, it is probably a good time to be considering a switch to this software.

Andrew D. Lyons is a visual effects expert with more than 10 years experience working with several film and television post-production studios worldwide. Among his credits are Over the Hedge, Charlie and the Chocolate Factory, Stealth and The Day After Tomorrow. In addition, he received is doctorate from the University of Sydney for his research into audio-visual composition for virtual reality performance equipment.

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