Cube  Documentation

// rndmap.cpp: perlin noise landscape generation and some experimental random
// map stuff, currently not used

#include "cube.h"

float
noise(int x, int y, int seed)
{
	int n = x + y * 57;
	n = (n << 13) ^ n;
	return 1.0f -
	    ((n * (n * n * 15731 + 789221) + 1376312589) & 0x7fffffff) /
	    1073741824.0f;
}

float
smoothednoise(int x, int y, int seed)
{
	float corners = (noise(x - 1, y - 1, seed) + noise(x + 1, y - 1, seed) +
	    noise(x - 1, y + 1, seed) + noise(x + 1, y + 1, seed)) / 16;
	float sides = (noise(x - 1, y, seed) + noise(x + 1, y, seed) +
	    noise(x, y - 1, seed) + noise(x, y + 1, seed)) / 8;
	float center = noise(x, y, seed) / 4;
	return corners + sides + center;
}

float
interpolate(float a, float b, float x)
{
	float ft = x * 3.1415927f;
	float f = (1.0f - (float)cos(ft)) * 0.5f;
	return a * (1 - f) + b * f;
}

float
interpolatednoise(float x, float y, int seed)
{
	int ix = (int)x;
	float fx = x - ix;
	int iy = (int)y;
	float fy = y - iy;
	float v1 = smoothednoise(ix, iy, seed);
	float v2 = smoothednoise(ix + 1, iy, seed);
	float v3 = smoothednoise(ix, iy + 1, seed);
	float v4 = smoothednoise(ix + 1, iy + 1, seed);
	float i1 = interpolate(v1, v2, fx);
	float i2 = interpolate(v3, v4, fy);
	return interpolate(i1, i2, fy);
}

float
perlinnoise_2D(float x, float y, int seedstep, float pers)
{
	float total = 0;
	int seed = 0;
	for (int i = 0; i < 7; i++) {
		float frequency = (float)(2 ^ i);
		float amplitude = (float)pow(pers, i);
		total += interpolatednoise(x * frequency, y * frequency, seed) *
		    amplitude;
		seed += seedstep;
	}
	return total;
}

void
perlinarea(const struct block *b, int scale, int seed, int psize)
{
	srand(seed);
	seed = rnd(10000);
	if (!scale)
		scale = 10;
	for (int x = b->x; x <= b->x + b->xs; x++) {
		for (int y = b->y; y <= b->y + b->ys; y++) {
			struct sqr *s = S(x, y);
			if (!SOLID(s) && x != b->x + b->xs && y != b->y + b->ys)
				s->type = FHF;
			s->vdelta = (int)(perlinnoise_2D(
			    x / ((float)scale) + seed,
			    y / ((float)scale) + seed, 1000, 0.01f) * 50 + 25);
			if (s->vdelta > 128)
				s->vdelta = 0;
		}
	}
}