DOOM Fire Effect

This code is based on http://fabiensanglard.net/doom_fire_psx/index.html

Requirements

• Visual Studio 2017
• SDL 2.0

Notes

I do not think I can write this better than original Fabiens article, but only interesting thing I would like to note is this pice of code

int RandomeNumber = rand() % 3;
m_FrameBuffer[y - 1][x] = m_FrameBuffer[y][x] - (RandomeNumber & 1);

and in original Fabiens javascript

 function spreadFire(src) {
    var rand = Math.round(Math.random() * 3.0) & 3;
    firePixels[src - FIRE_WIDTH ] = firePixels[src] - (rand & 1);
 }

Why in the world would he chose a random number between 0 and 2 Math.random() * 3.0 then he forces it to be either 0 or 1 (rand & 1) ?

The answer is Probability! The code want to give the probability 1/3 to go and look and the below line.

If we have 0 to 2 as random number in binary (00, 01, 10), you can notice that 1 in the least significant bit is accruing 1/3 times. The rand & 1 is to mask it out.