code/x11-random/worley_noise.c

#define _XOPEN_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <X11/Xlib.h>
#include <math.h>

#define WIDTH 1280
#define HEIGHT 720
#define SEED 200

#define POINTS 15

static int seed_offset = 1;

struct point {
    int x;
    int y;
};


double dist_p1_p2(int p1x, int p1y, int p2x, int p2y)
{
    double pA, pB;
    pA = p1x - p2x;
    pB = p1y - p2y;

    return sqrt(pA * pA + pB * pB);

}

void draw_pixel(Display * di, Window wi, GC gc, int x, int y, int color)
{
    XSetForeground(di, gc, color);
    XDrawPoint(di, wi, gc, x, y);
}

float rand_0_1()
{
    return drand48();
}

void sort(double *arr)
{
    int arr_size = POINTS;
    int i, j, aux;
    for (i = 0; i < arr_size; i++) {
	for (j = i + 1; j < arr_size; j++) {
	    if (arr[i] > arr[j]) {
		aux = arr[j];
		arr[j] = arr[i];
		arr[i] = aux;
	    }
	}
    }

}

int map(int value, int min, int max, int map_min, int map_max)
{
    double R = (double) (map_max - map_min) / (double) (max - min);
    double y = map_min + (value * R) + R;
    return (int) y;
}

void worley_noise(Display * di, Window wi, GC gc)
{
    int x, y, i;
    int c;
    int noise_space[WIDTH][HEIGHT];
    double dist[POINTS], sdist[POINTS];
    struct point p[POINTS];


    for (i = 0; i < POINTS; i++) {
	p[i].x = (int) (rand_0_1() * WIDTH);
	p[i].y = (int) (rand_0_1() * HEIGHT);
    }

    for (x = 0; x < WIDTH; x++) {
	for (y = 0; y < HEIGHT; y++) {
	    for (i = 0; i < POINTS; i++) {
		dist[i] = dist_p1_p2(x, y, p[i].x, p[i].y);
		sort(dist);
	    }
	    int d1 = map(dist[0], 0, WIDTH / 2, 200, 0);
	    int d2 = map(dist[1], 0, WIDTH / 2, 200, 0);
	    int d3 = map(dist[2], 0, WIDTH / 2, 200, 0);

	    /* 0x000000 rgb value where 
	     * 16 r
	     *  8 g
	     *  4 b*/
	    c = (d1 << 16) + (d2 << 8) + d3;
	    noise_space[x][y] = c;
	}
    }

    for (x = 0; x < WIDTH; x++) {
	for (y = 0; y < HEIGHT; y++) {
	    draw_pixel(di, wi, gc, x, y, noise_space[x][y]);
	}
    }
}

void redraw(Display * di, Window wi, GC gc)
{

    XClearWindow(di, wi);
    worley_noise(di, wi, gc);
    XFlush(di);
}

int main()
{
    Display *di = XOpenDisplay(getenv("DISPLAY"));
    if (di == NULL) {
	fprintf(stderr, "ERROR: No display");
	exit(EXIT_FAILURE);
    }
    int x = 0, y = 0, width = WIDTH, height = HEIGHT, border_width = 1;
    int sc = DefaultScreen(di);
    Window ro = DefaultRootWindow(di);
    Window wi = XCreateSimpleWindow(di,
				    ro,
				    x,
				    y,
				    width,
				    height,
				    border_width,
				    BlackPixel(di, sc),
				    WhitePixel(di, sc));

    XMapWindow(di, wi);
    XStoreName(di, wi, "Default Window");

    GC gc = XCreateGC(di, ro, 0, NULL);

    XSelectInput(di, wi, KeyPressMask | ExposureMask);
    XEvent ev;
    int quit = 0;
    while (!quit) {
	if (XPending(di) > 0) {
	    int a = XNextEvent(di, &ev);
	    if (ev.type == KeyPress) {
		printf("KeyPress %x\n", ev.xkey.keycode);
		if (ev.xkey.keycode == 0x18)
		    quit = 1;
	    }
	    if (ev.type == Expose) {
		redraw(di, wi, gc);
	    }
	}
	redraw(di, wi, gc);
    }

    XFreeGC(di, gc);
    XDestroyWindow(di, wi);
    XCloseDisplay(di);
    return (EXIT_SUCCESS);
}