Some years ago I played a pc game, named The Devil Inside. It was a classic third person shooter, survival horror game, where Dave, the main character, walks through a hounded place shooting the creatures of the night. In level two, if I recall, Dave reaches a very dirty (actually disgusting) toilet. There, after shooting down the inhabitant (a zombie), Dave walks inside to search for hidden items. And then, suddenly, before he was able to reach the toilet paper, the unexpected happed!! Dave fell into a hole. It was just if the world had suddenly and mysteriously disappeared. I could still see him. Into the darkness, with some dim light coming from the hole above his head, he was still alive and capable of some moves, but that was it. At first I thought this was just a challenge in the game, and tried several ways to rescue my hero, with no success. At the end I realized that this was not a part of the game but rather an anomaly. Poor Dave was trapped out of his world, into nowhere, and there was no way he could get back inside. Later I found out that he was trapped into what is called a BSP hole.
In computer games a BSP hole (often connected with the Hall of mirrors effect) is a hole created into the boundaries of the game’s artificial “world”. These boundaries, and consequently the world, are made up of polygons fitting together. If, for some reason (a bug in programming or rendering let’s say), some polygons don’t fit well, a hole is appearing. If a character cross this point, a point that normally characters of the game are not supposed to go, he is actually stepping out of his world’s borders or, to be more precise, stepping into nowhere, with no possibility of returning.
In modern games, this phenomenon is usually prevented, and in the rare cases it actually happens, programmers provide a really simple solution to avoid stalling of the character;touching such a hole results to instant death.
I don’t know why I’ m telling these things. I’ m not a game developer, so my problem, after all, is not technical. I usually worry about the holes of the real world.