Gamasutra - Features - "Algorithms for an Infinite Universe" [09.17.99]


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By Guy W. Lecky-Thompson
Gamasutra
September 17, 1999

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Features

Contents

Introduction

Predictably Random Numbers

Name Generation Techniques

Generating Random Terrain

Plot Sequencing

Code Listings

Listing 1

Listing 2

Listing 3

Listing 4

Listing 5

Listing 1.cpp

// Pseudo Random Number Generation Example

#include <stdio.h>
void main(void)

{

// Choose two large integers such that
// one is double the other

unsigned long ulGenerator1;
unsigned long ulGenerator2;
ulGenerator1 = 4096;
ulGenerator2 = ulGenerator1 * 2;

// Choose a seed value that is between 1
// and the smaller of the large integers

unsigned long ulSeed = 1024;

// Choose a value Max, that represents the highest number that is to be returned

unsigned long ulMax = 2048;

// Generate a series of 10 numbers

for (int i = 0; i < 10; i++)

{

// For each iteration, Multiply Generator1 by
// the seed, and add Generator2

ulSeed = ulGenerator1 * ulSeed;
ulSeed = ulSeed + ulGenerator2;

// The new seed is remainder of this value
// divided by Max

ulSeed = ulSeed % ulMax;

// Return seed as the random value

printf("Iteration : %d %ld\n",i+1,ulSeed);

}

Listing 2