Racing across the war torn planet of Draenor, The Grimrail carries a cannon powerful enough to shatter the defenses of Shattrath City.
In a daring final effort to stop the delivery and save the city, heroic adventurers venture into the Grimrail Depot to rush aboard the train as it leaves the station; fighting their way to the conductors car and ensuring this is the Iron Horde’s last delivery.
Less heroic adventurers jump off the train and leave Shattrath to its fate, opting instead to explore the illusions that are really at play in the dungeon, and long time viewers already know which one we’re doing.
To escape the Grimrail yourself, just grab a demon hunter and use the method showcased in the video above to get out on your own.
Once off the train, you may notice that rather than watching it race away into the distance you’re still standing next to it. This is because the train isn’t actually moving. Instead, the landscape is being slid backwards past the train as The Grimrail sits on a stationary invisible platform.
Heading away from the train we pass behind the landscape and get a better picture of what’s really going on. A flat, unmoving section of ground texture 20 feet below the train conceals that the train depot where we fight the first boss is actually hidden directly below the second half of the dungeon.
Circling back towards the train we can jump up and hook ourselves on the iron spikes on the moving sections of landscape (more detailed instructions are also in the video above), transferring ourselves onto them and causing the train to appear to rocket into the distance. In reality what’s happening is we’re now moving backwards away from the train.
The way the Grimrail Depot is set up, a series of random map segments are all cycled in a constant loop backwards past the train. This creates the illusion of a continuous changing landscape from the perspective of the train. Once a map segment has passed by it teleports back to the front of the order, where it waits to be sent past the train once again.
Because the various sections of landscape are sent past the train in a random order, every section has been designed to seamlessly overlap with each other in order to create the illusion of one constant landscape from the perspective of players on the train.
Jumping off of the spikes as the train approaches causes us to fall through the map and land on an untextured section of terrain underneath the dungeon. From here we can look at the working of the dungeon from below, watching the sections of map slide backwards past the train before teleporting back into a stack in front of it.
The Grimrail Depot showcases how developers can use optical illusions to trick players into thinking they’re rocketing forward at hundreds of miles an hour, when in reality they’re standing completely still.