Issue: Volume: 23 Issue: 6 (June 2000)

REVIEWS: Houdini 4.0

by George Maestri

The newest release of Side Effects' Houdini 3D graphics and special effects system features, among other things, a new user interface, innovative VEX (vector expressions) scripting technology, and a port to the Linux operating system, making version 4.0 the most significant Houdini release to date.

Houdini is known for its object-oriented operation. To perform tasks such as modeling, texturing, shading, and animation, you link together operators, called OPs. You can choose from a half dozen OPs, including SOPs (surface operators), POPs (particle operators), CHOPs (channel operators), SHOPs (shader operators), COPs (compositing operators), and TOPs (texture operators). You connect these operators using Houdini's editors to create complex and customized pipelines of operations. The key point is that the operations remain available throughout the life of a project, so you can tweak these building blocks at any point.
Houdini 4.0's new interface is much more efficient than in past versions and includes the ability to tear off windows so that they float above the desktop.

What users will notice first in 4.0 is the interface, which eliminates much of the hopping between different operators that was cumbersome in earlier releases. For instance, in past versions, you had to move from the POPs to the CHOPs module to go from editing a scene's particles to editing its animation data. Now, you can configure the interface so that the POP and CHOP editors show up on the screen at the same time.

Also, you can now save window configurations as custom desktops, so you can have one desktop just for modeling, another just for animation, and so on. Side Effects also created several floating windows for features such as Houdini's render manager, which helps eliminate interface clutter.

With these changes, Houdini's interface is a nice evolution from its previous look and feel. Users coming over from other packages, however, might need to get used to Houdini's philosophy. Houdini is unlike a typical 3D package because instead of manipulating objects, you manipulate their operators. As such, whenever I review Houdini, I need a day or so to get used to this workflow. But after I do, I find it to be a productive way to model and animate, and I can see why many technical directors swear by Houdini.

Another significant new feature is the VEX scripting language, which enables you to write your own operators. Loosely based on C++, VEX opens up Houdini to an unprecedented amount of customization. You can write a script that generates a custom type of surface, for example, or a CHOP that moves your objects according to another script.

In terms of character animation, version 4.0's Inverse Kinematics system enables users to limit bone rotations for a more realistic skeleton-the elbow can be limited so that it doesn't rotate backward, for example. The IK system can also perform other advanced tricks, such as use a spline to manipulate a skeleton and animate the length of a bone for squash-and-stretch applications. For facial animation, Houdini now offers automatic lip sync with its Phoneme and Voice CHOPs.

Also new is the addition of rigid body dynamics. Implemented as a POP, rigid body dynamics enables real-world physics to control motion and collisions between objects in a scene. I found the solver to be robust and the results natural. Still missing is soft body dynamics, which affects the shape of soft objects, such as a cube of Jell-O.

Houdini has always had strong Unix roots. Even the NT version ships with a version of the Unix C-Shell-a nice touch for the Unix-savvy. It comes as no surprise, then, that Houdini is the first major 3D package to be ported to Linux, a freely available, Unix-type operating system that includes true multitasking, virtual memory, shared libraries, demand loading, TCP/IP networking, and other features consistent with Unix systems.

Houdini 4.0 boasts other new features as well. For instance, Side Effects has added to Mantra, Houdini's renderer, such sorely needed shaders as Blinn, Lambert, Phong, Cook, Normal, Constant, Shadow, and TwoTone (cartoon). Rendering tests on these looked good; I liked the Blinn and Cook shaders a lot. Also new are procedural operators for items such as noise, marble, and wood. One of my favorites is the modulated erosion procedural texture, which erodes an object's surface based on the contents of a bitmap-great for aging effects.

The new interface, VEX scripting, and other general improvements make Houdini one of the most powerful animation and special effects tools available. This revolutionary system will continue to find a home on the desks of talented effects artists.

George Maestri is a writer and animator living in Los Angeles.

Price: $17,000
Minimum system requirements: SGI: IRIX version 6.2 or later; 128MB of RAM. NT: Windows NT 4.0; 450MHz Pentium III; 128MB of RAM. Linux: 450MHz Pentium III; 128MB of RAM.
Side Effects Software
Toronto, Canada