This Month in Physics History

October 1998: Trespasser Makes History As The First Video Game to Incorporate a Complete “Physics Engine” — And Flops

The Jurassic Park-themed game was the first to use code that crunches mechanics equations with lightning speed. The game was trailblazing, and its glitches disastrous.

By Liz Boatman | September 14, 2023

Credit: Courtney Howerton / APS

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The video game Trespasser, released in 1998, was promised by its developers to be revolutionary. Packed with visually dazzling dinosaurs and detailed sets, it paved the way for major advances in the “physics engine,” or the equation-crunching code that governs how objects interact in video games. It was, perhaps, one of history’s most daring feats of game development.

It also was one of history’s biggest video game flops.

In 1993, Steven Spielberg’s 1993 film Jurassic Park wowed audiences around the world with its realistic dinosaurs, who are brought back from extinction to tromp around a theme park on a fictional island. When the operation suffers a meltdown, dino mayhem ensues. The 1997 sequel, The Lost World, is set on a nearby island. (More mayhem.)

After the first film’s release, DreamWorks Interactive scrambled to create a cutting-edge, single-player video game, slated to launch in late 1997, whose storyline would take place a year after The Lost World’s plot. In the game, Trespasser, players control Anne, who becomes stranded on one of the dinosaur-ridden islands after a plane crash.

Despite developers’ grandiose promises, the game faced tremendous challenges, running over budget and schedule. When the game finally hit shelves a year late, the hype backfired. One reviewer branded Trespasser “an experiment gone horribly wrong.” Another described it as “the most frustrating game I have ever played … filled with boring gameplay and annoying bugs.”

Only 50,000 copies sold. By comparison, Duck Hunt, the 1984 game in which the player shoots at ducks while a bird dog mocks every miss, sold over 28 million copies. Minecraft has surpassed 238 million installations.

But Trespasser was the first video game to rely exclusively on classical mechanics — impulse, force of gravity, and multi-body collisions, for example — to govern motion and interaction during game play, by using a fully-fledged “physics engine” in its software. It was also the first game to incorporate “ragdoll physics,” in which a body is treated as a group of rigid shapes connected by joints on which gravity can act, like in real life. (Imagine a velociraptor you’ve killed tumbling down a hillside, instead of bouncing like a ball or falling over.)

Credit: Still shot from Trespasser (DreamWorks Interactive), uploaded by Phil Iwaniuk to TechRadar.com.

Trespasser was the first video game to use a fully-fledged “physics engine” in its software. It didn’t go quite to plan.

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Until the mid-1990s, most games were simpler, 2D side-scrolling games, like Super Mario Bros. But in 1996, Super Mario 64 saw enormous success with a 3D game environment, and other developers raced to follow suit. In 1997, a year before Trespasser’s release, developers released a James Bond-themed video game called GoldenEye 007. Although the game was designed mostly in shades of gray to speed up visual rendering, it had impressive 3D programming and was a commercial hit.

But GoldenEye 007 lacked a fully developed physics engine. Without this, certain actions, like death scenes, followed prescribed sequences. Each kill looked like the next. By contrast, Trespasser’s developers sought to build the most advanced physics engine ever — and that meant they had to develop the ragdoll physics, among other kinematic elements.

“Kinematic simulation was the core of what they were doing in Trespasser,” says computer science professor Seth Berrier, who teaches video game design at the University of Wisconsin-Stout. “The fact that they could just turn the ragdoll physics on and let the physics happen, that would have been a really big leap at the time.”

All those firsts are also the reason Trespasser flopped. “Trespasser was a victim of its own greatness,” says Berrier. “They discovered something way ahead of its time.”

Back in 1997, the average home computer had at most 32 MB of RAM, or short-term memory, crucial to running a game. Today, a typical laptop has 64 GB of RAM — 1,000 times more. Processor speeds have increased, too, from about 300 MHz in the late 1990s to more than 3 GHz today. Combined, that’s thousands more physics calculations a computer can churn through in a single second.

The biggest advance, though, was the GPU, a separate processor just for graphics. “While it’s called the graphics processing unit, it’s really just a linear algebra engine. You can use it to do any problem that reduces to a system of equations,” says Berrier. “Physics simulation was one of the earliest non-graphics applications of the GPU.”

Because most home computers didn’t have top-notch GPUs in 1998, gamers encountered pixelated imagery and glitchy gameplay in Trespasser, made worse by coding bugs in the game’s physics engine.

Some of the glitches were comical. For example, any fan of Jurassic Park knows that some of the film’s scariest moments occur when characters meet velociraptors indoors. But the game’s designers couldn’t put dinosaurs inside buildings because they would get stuck in the walls.

This bug stemmed from a timestep — the time interval between successive iterations of the motion in a scene — that was too large, a necessary measure to reduce computational costs. In a game, the player sees the graphical rendering of an object; what they don’t see is a less refined, invisible “box” that contains and moves with it. When the box penetrates another object’s box, a “penalty force algorithm” detects it and pushes back. This separates objects and governs how they meet, deflecting or deforming around each other.

But when the game’s timestep is too large, fast-moving objects can end up directly on top of each other — that is, with the same position coordinates — before the system has figured out that their boxes have intersected. “Then the [penalty] forces that are trying to push them away cancel out,” explains Berrier. “All of a sudden, both objects are stuck there.”

Credit: Still shot from Trespasser (DreamWorks Interactive), uploaded by Alan Chan to mobygames.com.

In one strange glitch in Trespasser, dinosaurs became stuck in walls.

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Other physics appeared to be missing entirely. In one in-game puzzle, the player must stack a series of crates to build an escape route. A review site called HonestGamers noted that, in these scenes, players had to be careful with how they positioned the crates, which tended “to slide off of one another as if they have no friction.”

“This is a classically difficult problem,” says Berrier. “When you have two rigid bodies, things can’t deform. What holds them together [in the real world]? Friction. But we don’t typically simulate friction because it’s very [computationally] expensive.”

Game developers today know how to solve this problem. “Nowadays the easiest solution is to turn [a set of objects] into a kinematic system,” he explains. “If something is on top of something else, you make it a ‘child’ of that by joining it to the ‘parent’ — not rigidly, so that it is still allowed to move on its own, but that any way the ‘parent’ moves, the ‘child’ will move as well.”

He says developers often use this technique with the player’s character. “If they get onto a movable platform, and you want them to move as if they’re in it, like an elevator, we just make that one continuous kinematic system.”

All these solutions were missing from Trespasser, in part because they didn’t exist yet, but also because the game’s developers ran out of time to build them. Although these fixes “are very expensive and not fun to implement,” Berrier says they’re crucial for making a game’s physics engine robust and its gameplay seamless.

Despite its woes, Trespasser will be remembered as the driver of many advances in video game design. For example, DreamWorks Interactive, which produced Trespasser, launched the Medal of Honor game franchise a year after, in 1999, building off the physics engine used in Trespasser. In 2004, Agent Bond returned to the game screen in GoldenEye Rogue Agent with a fully-fledged physics engine — this time, complete with ragdoll physics, which allowed Bond to lift “goons” with realistic motion and chuck them into other bad guys (a fan favorite).

In 1998, though, Trespasser’s “developers were in a new frontier with their physics engine,” says Berrier. “What students learn in a classroom nowadays … they were learning on the job, because it hadn't been done before.”

Liz Boatman is a staff writer for APS News.

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