C++ Fast-track for Games Programming Part 14: Fixed Point
In part Part 9 you worked with colours and were introduced to the noble art of bitmagic. Here’s a quick refresher: multiplying an integer value by a power of 2 can be done by shifting its (binary) bits to the left.
Division is similar, except this time you shift to the right. So for example, \(6a\) is equivalent to \(2^2a+2a\) which is equivalent to (a<<2)+(a<<1) using bit-shifting operations. Being aware of the number of bits in a variable is especially important if more than one number is stored in the bits of a 32-bit integer. This is is the case for 32-bit colours: Each of the red, green, and blue components each use 8-bits with the alpha component completing the 32-bits to represent a single pixel.