perlin.cpp File Reference

Code file for 2D Perlin noise with exponentially distributed gradients. More...

#include <stdlib.h>
#include <stdio.h>
#include <math.h>

Macros
#define	_USE_MATH_DEFINES
	Enable use of constant M_SQRT2 in math.h.
#define	B   0x100
	Perlin's B, a power of 2 usually equal to 256.
#define	BM   0xff
	A bit mask, one less than B.
#define	N   0x1000
	Perlin's N.
#define	lerp(t, a, b)   (a + t*(b - a))
	Linear interpolation.
#define	s_curve(t)   (t*t*(3.0f - 2.0f*t))
	Cubic spline.
#define	setup(i, b0, b1, r0, r1)
	Perlin's setup macro.
#define	at2(rx, ry)   (rx*q[0] + ry*q[1])
	Perlin's dot product macro.

Functions
void	normalize2 (float v[2])
	2D vector normalize.
void	swap (int &x, int &y)
	Swap two integers.
float	randomflt ()
	Get random floating point number.
void	initPerlin2D ()
	Initialize Perlin noise.
float	noise2 (float vec[2])
	COmpute one point of Perlin noise.
float	PerlinNoise2D (const float x, const float y, const int n)
	Compute turbulence value.

Variables
const float	FM_SQRT2 = (float)M_SQRT2
	Square root of 2 as a float.
float	g_fMu
	Mu, the gradient magnitude exponent.

Macro Definition Documentation

#define setup	(		i,
			b0,
			b1,
			r0,
			r1
	)

Value:

t = vec[i] + N;\
  b0 = ((int)t) & BM;\
  b1 = (b0+1) & BM;\
  r0 = t - (int)t;\
  r1 = r0 - 1.0f;

Function Documentation

void initPerlin2D

(

)

Initialize gradient and permutation tables.

Initialize the permutation, gradient, and magnitude tables.

float noise2

(

float

vec[2]

)

Compute a single octave of noise at 2D noise at a single point. This is mostly taken from Perlin's original code, with a few tweaks.

Parameters

vec	Point at which to evaluate noise.

Returns

Noise value between -1.0 and 1.0.

void normalize2

(

float

v[2]

)

Works by side-effect on the parameter v.

Parameters

v	2D vector as a 2-element array.

float PerlinNoise2D	(	const float	x,
		const float	y,
		const int	n
	)

Generate a cell of 2D Perlin noise.

Turbulence is also known as 1/f noise.

Parameters

x	X coordinate.
y	Y coordinate.
n	Number of octaves.

Returns

Noise value in the range -1 to 1.

float randomflt

(

)

Get random floating point number between -1 and 1. Uses rand() to do the heavy lifting.

Returns

Pseudorandom floating point number between -1 and 1.

void swap	(	int &	x,
		int &	y
	)

Works by side-effect.

Parameters

x	First value.
y	Second value.