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Ever wished you could knock down skyscrapers or submerge bridges under giant tsunamis like Godzilla? Now you can, thanks to Next Limit Technology's Real Flow 3D physical dynamics simulation software. And you don't have to clean up the mess when you're done.

Fast forward to today's animation world where digital Iron Man smashes his way through every imaginable virtual obstacle on the big screen, and you get a sense of how far we've come over the last forty years, roughly the same amount of time it took Moses to reach the Promised Land.

The armies of digital artists who toil in the fields of the movie studios use commercial 3D animation programs like Autodesk's Maya and Avid's XSI to produce these onscreen wonders. For a couple thousand bucks (or a few hundred, if you're a student) you can buy these very programs and run them on most any recently minted computer yourself.

But if you want to make water crash and splash the way it did in Titanic, or accurately pop the cork on a champagne bottle while the bubbly overflows the sides and the cork shoots across the room to cause a glass window to shatter into a zillion flying glass shards, you may need a little something extra. For cases like this you need a program like Next Limit's Real Flow 4.

WHAT REAL FLOW DOES

Programs like Maya have their own built in dynamic simulation routines, and they're quite powerful. You can simulate gravity, wind, and other natural forces as well as environmental elements like clouds, smoke, and dust. A lot of these simulations rely on masses of tiny particles swirling about to create the illusion of dynamic motion.

Real Flow also depends on particles to create its most dramatic effects, but Real Flow particles are smarter than the average 3D program's particles because they're aware of each other. For example, let's say you want to create one of the simplest liquid simulation effects, water pouring into a glass.

You can do this in Maya, but what happens is that the particle field that makes up the water only knows about the sides and bottom of the glass and the gravity that affects how the liquid flows into the glass. Once in the glass, it will simply pool up. But when Real Flow water hits the sides of the glass, all the particles collide, swirl, and splash against each other. The result is much more realistic and dramatic.

WHAT ELSE REAL FLOW DOES

It's easy to convert the viscosity of your liquids in Real Flow from water to heavy motor oil or even goopy tar. For even more fun, you can get multiple fluids with different density profiles to collide with each other as well as with all or some of the objects in your scene. You can also determine the degree of friction and stickiness connected to the objects the liquids interact with.

A lot of programs simulate large bodies of water, such as lakes or rivers, but most of them aren't terribly convincing. Next Limit's adddresse these deficiencies with a vengeance, deploying specialized tools to differentiate what happens not only above the surface of a body of water, but below it as well. You can also produce realistic pond ripples, and control an object's wake when it floats downstream. With a little work you can create realistic waves and control how they behave when they approach a shoreline.

RealFlow's flagship features relate to solving complex liquid interactions, but the program's also first rate at calculating other physically accurate nonlinear dynamic simulations. The Real Flow engine knows all about rigid bodies (e.g. a steel beam) and soft bodies (e.g. fat jiggling on a sumo wrestler). It's easy to set up hinge and pin constraints to simulate a swinging ball and chain that will knock objects over and smash them to pieces. The app also has some unique features such as fibers that can be jiggered to simulate effects like waving sea anemone tendrils.

In addition to natural phenomena such as gravity, wind, and drag, you can fine tune your simulation with forces that assign levels of attraction and repulsion to individual objects in your scene. You can control temperature parameters to literally build up a head of steam that'll blow the lid off a teakettle.

A feature I like a lot is a particle creation system that fills mesh objects with particle clusters that can then be acted upon by the abovementioned forces. From the other direction, you can convert particles into meshes that can be exported to your 3D application of choice. There's also a cool Wet Map texture generator that reflects light on an object differently depending on where it's been splashed.

REAL FLOW'S WORK FLOW

I like the Real Flow interface design a lot (longtime readers know this is a rare accolade from this camp). Everything you need is right in front of you, including a set of key icons, the principal control parameters, and an inclusion/exclusion palette to determine which elements in your scene interact with each other. I tested the program using two 1600 x 1200 pixel displays. I set up the Top, Front, Side, and Camera views on one screen, and the control panels on the other. The overall feel is similar to high end video post production packages like Flame and Inferno.

You can import objects from external files or scenes in the SD file format. After your simulation's complete, you export a new SD file to your 3D app for final tuning and rendering. There's also a plugin that lets you export particles and meshes to another application, including Maya, 3D Studio Max, Lightwave, XSI, Cinema 4D, and Houdini.

I found the general process of creating complex simulations in Real Flow pretty straightforward, but be warned that fine tuning them to your particular requirements can involve considerable effort. I spent a lot of time fiddling with all sorts of parameters, some of which were fairly predictable, while others produced radical effects from very small attenuations. The new version 4 of the program supports Python programmability, so you can set up some pretty complex time-dependent and event-based animation scenarios that would be difficult to pull off by just twiddling knobs.

The Real Flow manual leaves a lot to be desired. It covers the basics and shows some examples, but when it comes to this class of program, the devil's always in the details. The only way to figure out how things really work in a particular situation is to run a full-on simulation, which in some cases can take quite a while to set up and hours – or even days – to run, even on a powerful workstation.

A good library of presets to get new users started would be extremely useful. There's an unofficial forum at http://www.realflowforum.com/ where a community of Real Flow users trade tips and tricks about everything from the settings for accurately simulating dripping blood to sharing a script to generate properly fizzy beer bubbles. Digital Tutors (www.digitaltutors.com) sells a collection of Real Flow training DVDs that amount to the program's Missing Manual. They have some free demos you can watch on their web site.

I tested Real Flow on a 64-bit Windows XP workstation with dual AMD Opteron processors and 8 gigabytes of RAM. I was surprised at how efficient Real Flow is at allocating memory. I ran several fairly complex simulations that fit into less than a gigabyte of RAM. Other scenes maxed out the entire RAM count and begged for more.

I found it difficult to predict how long a simulation would take to render. Sometimes I was able to run simulations that required only a few seconds per frame to generate, but making certain crucial changes to the scene settings resulted in the same frames taking over an hour apiece to calculate, meaning that at 24 frames per second, one second of animation would require over a full day to compute.

THE WRAP

Real Flow retails for $2,700 list. If you're producing animations that involve splashing liquids, sweating beer bottles, or melting chocolate, you probably need Real Flow. And if you're just looking for a good time pushing pixels around, Real Flow's more fun than a barrel of monkeys.