Codex Gamicus

Jurassic Park: Trespasser (also known as Trespasser) is a video game, which was released in 1998 for Microsoft Windows after much hype and anticipation. The player assumes the role of Anne, the sole survivor of a plane crash on InGen's "Site B" one year after the events of The Lost World: Jurassic Park. With a fractured arm and only her wits, Anne must escape the remote island by solving puzzles and evading dangerous dinosaurs.

Trespasser's game engine was advanced for its time and required a fast computer to adequately display the game's detailed graphics without pixellation artifacts.[1] The game disappointed many reviewers and is often mocked,[2] but has a cult following and strong modification community to this day.


The game opens with John Hammond reading an excerpt from his memoirs. Hammond is a rich industrialist who used his wealth to assemble a scientific team which cloned dinosaurs. Intent on creating an amusement park showcasing his biological attractions, Hammond's park ultimately fails when the dinosaurs escape.[3] While Jurassic Park was built on Isla Nublar, off the coast of Costa Rica, the animals were raised at an alternate location, Isla Sorna also named "Site B".[4] Trespasser takes place a year after the events of The Lost World: Jurassic Park, where the general public has learned about the existence of Jurassic Park.[3]

The game opens on a dark apartment, where mail is piling up and a phone rings. When it goes to voice-mail, a woman named Jill leaves a message, expressing amazement that Anne (the apartment's resident) had actually gone ahead on a trip to the tropics. The message closes with Jill's comment, "I thought you HATED flying."

The scene changes to an unseen person closing and bolting an airplane bathroom door and then the sounds of retching can be heard. The plane suddenly bucks and an apparent malfunction occurs and the plane crashes.[5]

Anne awakens on the shores of an island (apparently the sole survivor of the crash), and proceeds to explore.[3] Anne learns she is on Site B, InGen's dinosaur breeding facility. Pursued by dinosaurs, Anne makes use of weapons left behind to defend herself as she explores. Following a monorail track into the island interior, Anne encounters dinosaurs such as Brachiosaurus, Velociraptor, Stegosaurus, Triceratops, Tyrannosaurus, Parasaurolophus, and Albertosaurus. After recovering security cards from an InGen town, Anne proceeds past a dam and to a large mountain. At the summit, Anne is able to call for help. After defeating the Alpha Velocirapror and its tribe that lives atop the mountain, she is rescued by helicopter. The game closes as Anne returns to her apartment. Jill calls and the message goes to the answering machine, saying she "better have a good damn reason for not calling," Anne wordlessly responds by tossing a raptor claw on her desk.


The entire game is played through the eyes of Anne (voiced by Minnie Driver).[6] There are only two cut scenes, one that begins the game and one that concludes the game, and an introductory video. There is occasional orchestral music, scored by Bill Brown. As she traverses the island, Anne will often talk to herself or remember clips of John Hammond's memoirs (voiced by Richard Attenborough) describing the creation (and downfall) of Jurassic Park.[4] There are no time limits or difficulty settings to adjust and only the first level has text prompts to aid players that are new to the game.



Screenshot showing a Triceratops

This game features no HUD.[2] Anne's health is represented by a heart-shaped tattoo on her breast that is filled in depending on the amount of damage she has taken; when it is completely full, and a chain appears around it, Anne is dead.[7] Anne's health regenerates quickly over time as long as she does not take further damage. The only way for the player to know how much ammunition is left in a particular weapon is by picking up and then weighing the weapon and specifically saying things such as, "About eight shots," "Feels full," and "Hasn't been used."[2] The actual level of realism has been debated because a number of Anne's characteristics, such as her ease at dropping items from her hand, is not very realistic. This example of not holding items is something that in real life is easy, yet difficult in the game.[8]

The arm[]

By pressing a key, Anne will extend her arm out in to the game world, allowing the player to pick up, swing, push and throw objects. This allows the player to create improvised weaponry, for instance: grabbing a large rock off the ground and bashing a velociraptor with it. Anne can move her arm in any direction, allowing the player to get a different feel of use for each weapon. However, this feature is extremely cumbersome, as it requires up to five buttons (maximum) to be pressed to fully manipulate the arm (picking up, dropping, moving, swinging, and rotating). This makes utilizing the arm in the heat of battle somewhat frustrating.[7] Anne can only carry two items at once and when bumping into things will often drop items.[4]

Further problems with the arm included a contribution to logical flaws in the promoted realistic portions of the game. For example, Anne could pick up steel girders that theoretically weighed a ton or more, and swing them around or toss them several feet with ease, but could not use this same arm to pull herself over a 3-foot (0.91 m) high embankment. The wrist mechanics had the capabilities of a contortionist, able to rotate 360 degrees several times over, yet Anne had no elbow, and often appears to flop about stupidly.[1]

In addition to picking up objects off the ground to use as weapons, Anne can find and use various other armaments. Such as keycards, discettes, and will even extend out one of her fingers in use for keypads. In keeping with the "hyper realistic" vision of the game, firearms have no crosshairs causing the player to align the gun by adjusting Anne's wrist, and Anne must manually move her arm to aim at dinosaurs.[2] This can make firing weapons especially difficult for inexperienced players. Anne can carry up to two weapons at a time. Weapons have been made to incorporate realistic recoil as if being held with two hands.

Once each firearm is empty, it serves little use except as a club when swung. Empty weapons cannot be reloaded, and so must be discarded and another one found.


The game was initiated by two former employees of Looking Glass Technologies, Seamus Blackley and Austin Grossman. With the film The Lost World: Jurassic Park expected to be a success and after securing the movie license, the pair approached several movie animation groups before signing with DreamWorks Interactive.[9] Adobe Photoshop 5 and 3D Studio Max were used to produce the game. A 3D model of the island was also built and digitally scanned.[9]

The game had a development period of more than three years.[citation needed] Money was the biggest hurdle in the development of Trespasser. The game severely went over-budget several times throughout its development.[citation needed] Second only to money was time, as the game had to be ready to meet the release of the The Lost World: Jurassic Park film. Originally the game was to be released in the fall of 1997.[5] However due to a number of problems the project was delayed by a year. The rush to release the game caused many features to be either cut, or left unfinished and unpolished.[9]

Due to difficulties coding the behaviour of both arms together developers had to ditch the left arm entirely.[10] A late shift in development effectively changed the game from survival horror to action shooter, and contributed to the many complaints the game received. Lack of experienced management and the use of artists who were unfamiliar with basic game development processes and 3D modeling has also been identified as a cause of problems.[5] Developers struggled for more than two years on some problems and in the end released a game that is set within a very large and open outdoor environment.[10]

The engine[]

The Trespasser engine was, and in many ways still is, unique. In 1998, it was one of the first engines to successfully portray outdoor environments full of hundreds of trees. Unfortunately, not many computers in 1998 could render the complex environments it generated. The result was the worst clipping one reviewer had ever seen with another finding the game experienced a slowdown and frame rate drops.[8][11] In addition, the Trespasser engine featured the first game world to be completely influenced by classical mechanics and was also the first game to use ragdoll physics.[12]

Object rendering[]

Perhaps the most advanced feature of the rendering engine was the ability to render objects like trees and rocks as 2D sprites, which, when close enough to Anne, would be replaced by their 3D counterpart.[9] Elements using this technique are known as "impostors". Unfortunately, this often led to an ugly "popping", where a low-resolution object suddenly "pops" into 3D immediately in front of the player. This is especially noticeable when playing the game at higher resolutions. The same kind of rendering technique was used in Shadow of the Colossus and Far Cry, although the latter uses higher resolution sprites and the total draw distance of 3D trees is set further away which has essentially eliminated the "popping" problem.[citation needed]

Trespasser's main problem was that development started before the 3dfx Voodoo 1 started the move towards 3D hardware.[9] Because of this some techniques, like the bump mapping and image caching were incompatible with graphics processing units. Near the end of development the programmers developed a renderer that drew bumpmapped objects in software and the terrain in hardware. Unfortunately most objects were bumpmapped so the speed advantages of hardware acceleration were negated. Trespasser used many textures for its mip levels and image cache, more than even the most advanced card of the time, the Voodoo II, could handle, and the game used the lower resolution textures in hardware mode instead of the high resolution ones available in software mode. This led to the strange situation that the game ran faster and looked better in software mode, while running in hardware mode meant the game ran slower and looked worse.[9]

Texture rendering[]

Trespasser was one of the first games to feature bump mapping and specular highlighting, however the effects are not overly apparent due to the lack of dynamic lighting and the fact that many of the models used grayscale versions of the regular textures instead of the displacement maps necessary to take advantage of bump mapping. Additionally, an effect was used to dynamically draw an animated texture to simulate the ripples in pools of water.

Terrain rendering[]

Trespasser used height mapping to render a full-sized island (split into chunks due to memory limitations).[9] Level designers would simply provide the Trespasser engine with a black-and-white image that detailed the height of the ground - the closer to white the shade of gray was, the higher the section of land would be elevated. Once a height map was created, objects such as buildings, weapons, dinosaurs and more would be hand-placed in a level.[9]


Trespasser features a robust physics system. But instead of accurate, per-polygon collisions, Trespasser uses a "Box System", where every object in the game acts as if it is encased in an invisible box. Additionally, Trespasser's physics are based on the Penalty Force Method, in which, when two objects collide - rather than stopping movement, the two objects push away from one another until they are no longer colliding.[9] This makes stacking objects difficult, and standing on top of objects even harder. It also led a great deal to a problem called interpenetration; where two objects will collide and then become stuck inside one another, unable to separate.[9] In the final release the dinosaurs were dis-allowed from making jump attacks and entering buildings to avoid interpenetration from occurring.


By far one of the most impressive features of Trespasser is a system dubbed by the creators as "Real-Time Foley". Theoretically, the Trespasser engine could produce the sound of any two objects colliding with one another at any speed or distance by dynamically mixing several sounds together on-the-fly.[9] To date, the only other significant game to feature this is Penumbra.[citation needed]

Artificial intelligence[]

Andrew Grant was Trespasser's chief artificial intelligence programmer.[13]Trespasser was designed to have a complex artificial intelligence routine, giving each creature on the island its own set of emotions; fear, happiness, hunger, among many others. Dinosaurs will fight together, enemy to enemy.[2] Dinosaurs would react to the player differently depending on what mood they were in.[13] Unfortunately, system bugs in the artificial intelligence routines made it so that dinosaurs would have drastic mood swings and would switch between mood-based actions so quickly, they would actually stop moving, unable to do anything at all. A quick fix was hard-coded in to the game that locked all dinosaurs’ anger at maximum, leaving all other emotions at zero.[9] This fixed the bug, but also negated all the work the team had done on programming the AI, leaving the dinosaurs ultimately simplistic in their goals.


In most PC games, characters have "animations" in the traditional sense: an animator scripts a sequence of movements for the 3D model to do, which are played at specified times. Every animation in Trespasser is done using inverse kinematics. Nothing in the game is pre-animated; every movement of every dinosaur is done through the dinosaur "thinking" to do it. Unfortunately, this ultimately looks awkward as dinosaurs sometimes stumble around oddly and contort to wild, impossible positions like a broken toy.[2]


Aggregate scores
Aggregator Score
GameRankings 57%[14]
Review scores
Publication Score
Allgame 4.0/5 stars[11]
Computer and Video Games 1.0/10[8]
GamePro 4.0/5 stars[4]
GameSpot 3.9/10[15]
IGN 4.7/10[1]
PC Zone 7.0/10[16]
GameRevolution B-[17]
Active Network 64%[6]

Before the release of the game, it was announced that Jurassic Park: Trespasser would revolutionize PC gaming. Unfortunately, after the game's release, reviews noted that it "failed to impress". Trespasser was a commercial failure with only 50,000 copies sold.[10] Reviews of the game were mostly negative; however some reviewers felt the game had a few positive elements. A few reviewers were impressed by the title's originality and scale. Many of the reviewers disliked the poor graphics performance on even the fastest, graphically accelerated PCs available upon the game's release. Despite the anticipation over the many "first attempts at" within the game's original development scope, the reality did not match the hype.[6][12] Instead of an awe inspiring game, people got what they felt was an "unfinished and rushed" game, that not many people enjoyed.[citation needed]

A Computer and Video Games review thought the game was a "dog" and gave it a score of 1 out of 10.[8] A Gamespot review by Elliot Chin described it as the most frustrating game he had ever played with "boring gameplay and annoying bugs".[15] Some of the complaints included the physics engine is needlessly complicating, levels were over-filled with box-stacking puzzles, exploration is tiresome because movement speed is far too slow, landscapes were barren with few dinosaurs, too many collision detection bugs, poor voice acting and a clumsy arm interface.[15] An IGN review was more favourable, describing the plot as "super-intriguing" with high praise for the realism of the game's physics engine.[1] Despite featuring a blocky and heavily pixelated environment that offered limited interaction, the dinosaurs were convincing and "looked and moved really well". Overall the reviewer felt the game was badly implemented but still ground-breaking.[1]

One GameRevolution review described the game's graphical engine as gorgeous with impressive real-time shadows and good water and particle physics. On the downside, the gameplay was very basic with the usual "key-finding, enemy-killing, button-pushing" of the FPS genre and when there was more than one dinosaur on-screen the game slowed considerably.[17] An Allgame reviewer didn't like the bugs and graphical glitches or the slow frame rate but concluded the game was a "ground breaking title that offers some great thrills, challenges, puzzles, and rewarding gameplay".[11] PCGamer thought the game got the atmospherics right.[2] PCZone felt the game could be quite frightening but that there were too many guns scattered around the island.[16] An Adrenaline Vault review liked the games originality and some tense moments, but disliked the critically bad flaws such as the slow treks, the lack of a real inventory system, the frustrating interface and there being too many guns lying around.[7]


As time went on, more and more fans got involved into making their own new levels using TresEd, fan-made software that allows the user to edit Trespasser.[4][5][7]


  1. 1.0 1.1 1.2 1.3 1.4 IGN: Trespasser Review. IGN. IGN Entertainment, Inc (1998-10-30). Retrieved on 2008-01-31
  2. 2.0 2.1 2.2 2.3 2.4 2.5 2.6 Craig Pearson (2007-05-16). PC Feature Long Play: Trespasser. PC Gamer. Future Publishing Limited. Retrieved on 2008-02-06
  3. 3.0 3.1 3.2 Jurassic Park:Trespasser Manual. 1998. Dreamworks Interactive. p5.
  4. 4.0 4.1 4.2 4.3 4.4 Peter Olafson (2000-11-24). Review: Trespasser (PC). GamePro. IDG Entertainment. Retrieved on 2008-01-27
  5. 5.0 5.1 5.2 5.3 John Alderman (1997-03-04). Jurassic Game Flouts Hyper-Real Physic. Wired. CondéNet. Retrieved on 2008-01-27
  6. 6.0 6.1 6.2 Byron Hinson. ActiveWindows -- Trespasser Review. Active Network, Inc. Retrieved on 2008-02-09
  7. 7.0 7.1 7.2 7.3 Emil Pagliarulo (1998-10-30). Trespasser: Adrenaline Vault. The Adrenaline Vault. Retrieved on 2008-01-27
  8. 8.0 8.1 8.2 8.3 Kim Randell (2001-08-15). PC Review: Trespasser. Future Publishing Limited. Retrieved on 2008-02-09
  9. 9.00 9.01 9.02 9.03 9.04 9.05 9.06 9.07 9.08 9.09 9.10 9.11 Wyckoff, Richard (1999-05-14). Postmortem: DreamWorks Interactive’s Trespasser. GamaSutra. Retrieved on 2009-11-21
  10. 10.0 10.1 10.2 Jim Hatley (2008-12-08). Jurassic Park: Trespasser - the revolutionary game that never was. Retrieved on 2008-02-08
  11. 11.0 11.1 11.2 Shawn Sackenheim. allgame ((( Trespasser > Review ))). Allgame. Macrovision Corporation. Retrieved on 2008-02-09
  12. 12.0 12.1 Macedonia, Michael (August 2006). "Why Graphics Power Is Revolutionizing Physics". Computer (Institute of Electrical and Electronics Engineers).;jsessionid=JPSQjbR65Kp25cTc1X1kTCXGNFmcfTyYyYTT4C1jbVcY1qBpXwDK!417175916. Retrieved 2008-02-09. 
  13. 13.0 13.1 Creating Intelligent Creatures. Computer Graphics World. PennWell Corporation. Retrieved on 2008-02-11
  14. Trespasser Reviews. GameRankings. CNET Networks, Inc. Retrieved on 2008-01-31
  15. 15.0 15.1 15.2 Elliot Chin (1998-11-19). Trespasser for PC Review. GameSpot. CBS Interactive Inc. Retrieved on 2008-01-31
  16. 16.0 16.1 Richie Shoemaker (2001-08-13). PC Review: Trespasser. PCZone. Future Publishing Limited. Retrieved on 2008-01-31
  17. 17.0 17.1 Calvin Hubble (2008-12-01). Trespasser video game review for the PC. Game CraveOnline Media. Retrieved on 2008-01-31

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