Every game that bounces a ball does some physics. For most of the 1980s and 1990s that meant special cases: a rule for the ball and the bat, another for the player and the floor, each written by hand for the game in question. A physics engine replaces the special cases with one general simulation. Objects are given mass, friction and bounciness, and the engine works out each frame how forces move them, where they collide and how they come to rest. That idea turned into a separate product at the end of the 1990s, and the period press followed it from one spectacular failure to a business worth buying.
Fast facts
- What it does: moves objects according to forces, detects collisions between them and resolves them, usually as rigid bodies, which “assume that there is no change in the geometry of the interacting bodies” (Edge, 2005).
- The ambitious failure: Trespasser (DreamWorks Interactive, 1998), with dinosaurs built from skeletons and “artificial muscle connections”; Computer Gaming World found “a technically promising engine that screws up gameplay”.
- The first vendors: MathEngine and Havok, which “launched their realtime physics engines at the end of the 1990s”. By 2005 Edge listed eight, including the open-source ODE.
- The first customers: racing games, because “the vehicle dynamics are a core part of the gameplay”.
- Hardware: Ageia’s PhysX chip went on sale in 2006; Nvidia bought Ageia in 2008, and the PhysX name lived on as Nvidia’s engine.
Trespasser
Computer Gaming World introduced Trespasser: Jurassic Park in March 1997 with Steven Spielberg calling it “the digital sequel to The Lost World: Jurassic Park”. It was being built at DreamWorks Interactive by a team under Seamus Blackley, a designer-programmer who had worked on Flight Unlimited, and every object in it was “defined in such a way that it acts and can be used realistically”. The dinosaurs were not animated in the usual way. “Blackley developed skeletal models for each of the dinosaurs represented in the game. Then, he connected the skeletons with artificial muscle connections. Each portion of the skeleton and musculature is assigned weight, strength, durability, etc. and, as a result, the model ends up handling skeletal and muscle movement according to authentic physical principles. Even the recoil during combat is handled according to this physical model.”
The game was out by the end of 1998, and Robert Coffey’s review in Computer Gaming World in January 1999, headed “Veloci-Craptor”, showed what the simulation cost. The player’s arm was physical too, raised, lowered and twisted from the keyboard, which made aiming “less precise”. The puzzles were mostly box-stacking, and although the engine was “commendable in creating an environment full of objects to be pushed and picked up (but not destroyed)”, “boxes fall every time you breathe on them”. It was slow: “once a few objects or creatures start filling up the screen, man alive, does the frame rate tank. And this is on a Pentium II 300 with 3D acceleration and scads of RAM”. And “collision detection is a joke, letting your character get snagged on walls and in bridges, and letting dinosaurs get tangled in fences until they die.” The review’s list of good points still found room for “Physics-based engine isn’t too shabby”.
That same month Edge quoted Scott Miller of 3D Realms: “The bottom line is that realistic physics do not always mean better gameplay. Trespasser is a perfect example of this.”
The 1999 survey
Edge opened 1999 by going through the genres and asking the programmers. “Although gameworld physics are still pretty rudimentary,” it wrote, “Edge expects to see the next great leap forwards in game programming being made in this area soon.”
Racing games were furthest ahead. Codemasters’ Richard Ogden explained that TOCA 2 modelled a car as linked systems, chassis, suspension, tyres and aerodynamics, each handled separately and then joined, and that the model was “in its third iteration after being used in the original TOCA, as well as in Colin McRae Rally”. It was still “very simple when compared to the kind of calculations that would be done by, say, engineers analysing the performance of a real racing car”. Once graphics chips took over transformation and lighting, he expected “more CPU resources free to handle the physics”: tyres “actually having the rubber deforming and wearing out, temperature changing”.
Mark Cale of System 3 set physics against motion capture, which he called “replaying an animated sequence. You could think of it as pre-stored physics, not true real-world physics.” Jez San of Argonaut described the problem an engine would solve for platform games: “In the past, platform games have had to have special case code written to handle each possible interaction that the player may want to have with each object in the game world”, where a general engine would be “more elegant and intuitive for both the gamer and the development team”. Phil Drinkwater of Silicon Dreams thought that “the physics aspect of sports games is in its infancy”, and that driving players’ bodies by “the forces applied to muscles and gravity on the joints” was “too complicated at the moment”; programmers would use inverse kinematics instead. Miller described what 3D Realms was doing with Max Payne: “Bullets and projectiles actually travel at their proper speeds, rather than moving instantaneously as in previous games.”
The middleware
The leap came as a licence rather than as each studio’s own work. The Oxford company MathEngine, with its engine Karma, and Dublin’s Havok sold the first general-purpose real-time engines at the end of the 1990s. Looking back in March 2003, Edge explained why they caught on: physics middleware “made its initial impact not by providing developers with a set of new features but because it offered existing features cheaper and faster. The result was that the first wave of titles enabled by the technology were concentrated within realistic genres such as vehicle-based racers.” Havok’s Steve Collins gave the reason: “With a car game, the vehicle dynamics are a core part of the gameplay, so developers were happy to spend processing resources simulating high-fidelity dynamics.” Character animation became another application: ragdoll physics uses constrained bodies to make a character react to forces and collisions. That entry follows the technique from early experiments to its use in games.
Half-Life 2 (2004), built with physics derived from Havok, made physics something the player used. Reporting from the Game Developers Conference in March 2005, Edge said it had “incarnated physics into gameplay thanks to the introduction of the gravity gun”.
That report printed a panel of eight vendors:
- Havok, “the standard by which the others are judged”, with Half-Life 2 and Halo 2 among its games.
- Criterion’s RenderWare Physics, “based on MathEngine’s Karma physics solution, the rights to which Criterion acquired in 2003” (see RenderWare).
- Ageia, which had bought the Swiss company Novodex; Novodex’s engine was in Epic’s Unreal Engine 3.
- Meqon, a Swedish university start-up whose big break was being chosen for 3D Realms’ Duke Nukem Forever.
- Oxford Dynamics’ FastCar, which claimed “up to 100 cars on a PS2”.
- ODE, “a widely used open source library”, “mainly the work of ex-MathEngine coder Russell Smith”.
- Newton Dynamics, and Tokamak, “another free physics engine”.
Physics hardware
The same conference introduced a new idea: a separate chip for physics, as the 3D card had been for graphics. Ageia’s chief executive, Manju Hegde, said of its PhysX chip: “The limit of physically modelled bodies for current games is anything from 30 to 100. With PhysX, we can do over 30,000.” Epic’s Mark Rein said, “In our current Unreal demo, we can roll 600 boulders down the hill. With Ageia’s chip that could be thousands.” Ageia’s investors had put in $38 million, and add-in boards were expected to cost “from $100 to $400 (£53–£213)”. Edge saw the catch at once. Developers could not assume players owned the chip, so early games would be “limited to using it for what’s called cosmetic physics: cloth, fluid or hair simulations that don’t affect how a game plays”. Meqon’s Marcus Lysén thought that split, between “gameplay physics” and “cosmetic physics”, would last.
The magazine ended on a joke at the industry’s expense: “So will 2005 be the year of physics? Of course, just as every year has been since 1999.”
PhysX went on sale in May 2006. Edge reported that the bigger shock was Ageia’s business model: it gave its software engine to developers at a nominal cost if they supported the chip, and over 100 games were in production with it. Ageia had bought Meqon as well as Novodex, and taken in what remained of MathEngine. Havok, whose engine cost a six-figure sum, answered with Havok FX, physics on graphics cards. Nvidia bought Ageia in 2008. When Edge visited Zurich in 2013, Nvidia’s Swiss office, which had begun life as Novodex, was working on the renamed Nvidia PhysX engine, used in games such as Batman: Arkham City and Metro: Last Light and built into the Unreal Engine. Havok went to Intel in 2007 and to Microsoft in 2015.
Sources
- Computer Gaming World issue 152, March 1997: Trespasser: Jurassic Park preview (Spielberg; Blackley; objects that act realistically; the skeletons and muscles).
- Robert Coffey, “Veloci-Craptor”, Trespasser review, Computer Gaming World issue 174, January 1999.
- Edge issue 67, January 1999: physics feature (Richard Ogden of Codemasters, Mark Cale of System 3, Jez San of Argonaut, Scott Miller of 3D Realms, Phil Drinkwater of Silicon Dreams).
- Edge issue 72, June 1999: “Oxford-based MathEngine”.
- Edge issue 121, March 2003, Codeshop, “The next step for physics”: middleware’s first wave and Steve Collins on racing games.
- Edge issue 149, May 2005, pp. 66–71, “Beyond the valley of the ragdolls”: GDC 2005; Half-Life 2 and the gravity gun; Ageia, PhysX, Hegde, Rein, investment and prices; cosmetic physics; Lysén; “Physics: a primer”; the vendor panel.
- Edge issue 164, July 2006, “The physics of middleware”: PhysX on sale in May; Ageia’s pricing and over 100 games; Meqon, Novodex and MathEngine; Havok’s six-figure price and Havok FX.
- Edge issue 255, July 2013: Nvidia’s purchase of Ageia in 2008, PhysX in Batman: Arkham City, Metro: Last Light and the Unreal Engine, and the Zurich office.
- For Havok’s own history, including Intel (2007) and Microsoft (2015), see the Havok entry and its sources.