So I understand the concept for movies that are on DVD or Blu-Ray, as the disc spins the encoded data of the image that is on the disc is more or less read by the disc-player and displayed on the screen. But movies are linear and the disc just has to spin with the laser moving in a little every rotation and voila, movie I suppose. But with video games how are all the moving parts of the game, and my inputs and whatnot, read by the system off the back of a disc? Wouldn’t various parts of the code be in differing places on the disc? How does it jump back and forth between disc locations so quickly? How much of the game I’m playing is actually a result of the information on the disc, and how much comes from the part that I have to download whenever I put in a new game’s disc? Is the disc essentially just an installer wizard that allows me to download the actual game?
In: Technology
The actual program that determines how the game runs and behaves (its engine) is fairly small compared to the capacity of both the disc and the console’s memory. So, when you launch the game, the bulk of the instruction sets the console will need to run the game are loaded into memory from storage so that the processor can do its job. The processor does not need to constantly refer back to instructions on the disc, because all of those instructions have been loaded into memory.
However, your console has less memory than the disc has capacity. So, it can’t load everything. As the bulk of what’s taking up space on that disc is graphics and audio, the console copies only the graphics, sound, and animation it needs for the section of the game you’re in. That’s why loading screens exist; the console is pulling the data it will need for that section from disc (or storage) into memory.
Usually, the program can anticipate what information it will need, so it doesn’t have to look for it on the disc. This is called *predictive loading*, and basically means that the program can “guess” what it’s going to need next (you’re on Level 3, so we’re going to need Level 4 pretty soon – preload it). However, if you do something a little unusual, like backtrack, it has to seek for the Level 2 assets and load them.
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