-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.
-The Trespasser engine featured the first game world to be completely influenced by Newtonian physics and was also the first game to use ragdoll physics.
-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. 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.
-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.
-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. To date, no other game is known to have a similar feature.
-Andrew Grant was Trespasser's chief artificial intelligence programmer. 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. Dinosaurs would react to the player differently depending on what mood they were in. 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. 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.
