Bounds Checking and Hit Detection

Bounds checking and hit detection are two very common and important tasks associated with sprites. Bounds checking is a term used to describe the process of limiting a sprite's possible range of motion. For example, you might want to limit a given sprite to keep it from moving off the screen. To do so, you can check the values for the sprite's location, which you'll probably keep in a RECT structure, and prevent them from changing beyond the limits of the screen resolution. DirectDraw doesn't provide bounds checking services, but you can easily implement a bounds checking scheme in C/C++ alone. Clipping, on the other hand, is supported by DirectDraw. For more information, see Clippers.

Hit detection, or collision detection, refers to the process of checking whether one or more sprites occupy the same place. Most hit detection schemes involve checking to see if the bounding rectangles for one or more sprites overlap. Because there are so many different types of hit detection schemes with an equally varied number of uses, DirectDraw doesn't support them for you, thereby giving you the freedom to implement a hit detection scheme that meets your application's needs.