How can I best generate a static array of random number on demand?

Question

An application I\'m working on requires a matrix of random numbers. The matrix can grow in any direction at any time, and isn\'t always full. (I\'ll probably end up re-imple

Answer 1

What you're talking about is typically called "Perlin Noise", here's a link for you: http://freespace.virgin.net/hugo.elias/models/m_perlin.htm

The most important thing in that article is the noise function in 2D:

  function Noise1(integer x, integer y)
    n = x + y * 57
    n = (n<<13) ^ n;
    return ( 1.0 - ( (n * (n * n * 15731 + 789221) + 1376312589) & 7fffffff) / 1073741824.0);    
  end function

It returns a number between -1.0 and +1.0 based on the x and y coordonates alone (and a hard coded seed that you can change randomly at the start of your app or just leave it as it is).

The rest of the article is about interpolating these numbers, but depending on how random you want these numbers, you can just leave them as it is. Note that these numbers will be utterly random. If you instead apply a Cosine Interpolator and use the generated noise every 5-6 indexes, interpolating inbetween, you get heightmap data (which is what I used it for). Skip it for totally random data.