noise.qh

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#pragma once
 
// noises "usually" start in the range -1..1
entityclass(Noise);
classfield(Noise).float noise_baccum;
classfield(Noise).float noise_paccum;
classfield(Noise).float noise_paccum2;
classfield(Noise).float noise_paccum3;
classfield(Noise).float noise_bstate;
 
ERASEABLE
float Noise_Brown(entity e, float dt)
{
    e.noise_baccum += random() * sqrt(dt);  // same stddev for all dt
    return e.noise_baccum;
}
ERASEABLE
float Noise_Pink(entity e, float dt)
{
    float f;
    f = dt * 60;
    // http://home.earthlink.net/~ltrammell/tech/pinkalg.htm
    if (random() > (0.3190 ** f)) e.noise_paccum = 0.34848 * (2 * random() - 1);
    if (random() > (0.7756 ** f)) e.noise_paccum2 = 0.28768 * (2 * random() - 1);
    if (random() > (0.9613 ** f)) e.noise_paccum3 = 0.43488 * (2 * random() - 1);
    return e.noise_paccum + e.noise_paccum2 + e.noise_paccum3;
}
ERASEABLE
float Noise_White(entity e, float dt)
{
    return random() * 2 - 1;
}

ERASEABLE
float Noise_Burst(entity e, float dt, float p)
{
    if (random() > (p ** dt)) e.noise_bstate = !e.noise_bstate;
    return 2 * e.noise_bstate - 1;
}