3D ( And 2D ) Game Engines, Part 2

What is true of all game engines?

1. The more you understand simple geometry and graphing, the better. Coordinate systems are the way to present things to the human eye. This should be pretty obvious, but as you go from novice to pro, you'll quickly learn that there are things about your own perception that you never noticed.

2. Collisions and physics always use the same basic principles. As a matter of fact, advanced physics libraries such as Bullet and Newton ( ala Portal ) can be just as beautifully applied to 2-D as 3-D. One big difference is that in 2D, you can get away with collision using rectangles more easily, or even do a check on pixel overlapping.

3. Everything is an illusion. There is no physical space occupied by the hero of your game. Consequently, you will need to use a number of tricks that don't really fit reality. In 3D, we use a system called "Paging" to erase polygons that are hidden behind other polygons, so that the system has to do less work. There are also texture tricks that make it appear as if surfaces are reflecting ( called "environment mapping" ) when they're actually doing very little work. 2D has its own set of eye tricks.

4. You must care about your resources. This relates to the paging concept in 3. If you've only worked with text based applications, you're probably used to being able to do whatever you want. With even the most basic 2D graphics, however, this is not so. You have to watch your memory usage, only load what's needed, unload what you're done with, and above all, have a solid data structure to manage these operations.