Houdini's powerful character tools include the new channel editor (shown here). Also shown is Houdini’s new Flipbook keyframe feature that allows the animator to make quick timing decisions. All images © Side Effects Software.

In the contest for world domination in visual effects, Side Effects Software is an underdog. In terms of sheer numbers, it is miles behind market-leading vendors such as Alias, Discreet and Softimage, and the pool of Houdini-trained talent is proportionately small. However, the list of studios that do use Houdini is impressive, and growing, and includes luminary companies such as Sony Pictures Imageworks, Rhythm & Hues, Disney and Digital Domain.

While Houdini is a power-packed application (prices range from $1,299 to $17,000, depending on feature set), new users will quickly discover that its limits are more in the density of the interface than in what it can do. For this reason Houdini is commonly regarded as a "technical director's" package. A huge amount of learning goes into mastering the application, but a skilled TD can readily build projects that lend themselves well to multiple iterations of art direction and cycles of manipulation by effects supervisors and other artists. In production environments, this iteration loop is such an integral part of effects development that it can eclipse other issues, such as the quantity of user-friendly out-of-the-box features, or effects bells-and-whistles.

Houdini projects are based on visual networks of operators, or "Ops," which are containers for geometry, particle systems, animation, textures or actions — anything you can represent in a 3D scene. These networks allow an artist to build intuitive flow-diagram relationships, and the ease of manipulating this flow, and inserting new logic at any step, is the hallmark of Houdini. Everything is procedural, and can be manipulated by selecting the right node and modifying the data it contains.

Houdini 7 is a compellingly powerful effects animation package that can fit into almost any production environment.

To build a simple demo file rocket, for example, you would chain together a series of SOPs, or Surface Operators. (One of the idiosyncrasies of Houdini is the necessity of starting with a default geometry object, which is then replaced by the type of geometry you actually want to use.) You start with a Nurbs tube SOP then add a cap SOP for the nose cone. The fins are defined with a chain of SOPs: curve, extrude, xform, xfrom, fuse, polybevel and copy. Finally, the rocket body and fins are combined with a merge SOP and transformed with another xform SOP.

There is nothing particularly daunting or difficult about working with Houdini's Ops — in many ways the interface is comparable to using 3ds max's history stack, or to manipulating nodal dependence diagrams in Maya's Hypergraph. As in Maya, which lets you move easily in and out of its Hypergraph or Hypershade editors to see projects in an outline or other views, Houdini gives you ways of looking at projects without necessarily having to decipher long chains of procedural relationships. Still, to work in Houdini, you're going to have to buy into its flow-chart workflow, whether or not you think you have any need for parametric control at every step the way.

One concession Side Effects Software makes to the idiosyncrasies of different production environments is that the interface is highly malleable and customizable. Various production layouts can be saved as "desks," and these can be quickly enlisted to present important components in a useful way. The interface overall is fast and easy to use once you master the various hot keys and come to grips with the fact that all tools, however unrelated, live in large textual lists, and the only way to effectively access them is to hit the tab key and type their names to select them from the list. In practice, this approach is pretty fast, but it makes for tough learning, especially when you don't know what tools are available for a certain type of task, much less what it might be named.