matrix.c

#include <stdlib.h>
#include "ui.h"

#define NUM_DRIPS 250
#define PROB_DRIP_SPAWN 0.65
#define PROB_DIM 0.55
#define PROB_CHANGE 0.95
#define RANDOM_PRINTABLE_CHARACTER (33 + (rand() % 94))

typedef struct {
    int x, y;
    bool live;
    bool bright;
} drip;

cell matrix[MAXX][MAXY];
drip drips[NUM_DRIPS];

double rand01() {
    return (double)rand() / (double)RAND_MAX;
}

void init_drips() {
    for(int i = 0; i < NUM_DRIPS; i++) drips[i].live = false;
}

void matrix_init() {
    // set the matrix all to black
    // move this later to matrix.c
    // x, y instead of i, j
    for(int x = 0; x < MAXX; x++) {
        for(int y = 0; y < MAXY; y++) {
            matrix[x][y].char_value = 0;
            matrix[x][y].intensity = 0;
        }
    }
    // init drips
    init_drips();
}

void fade_n_change_matrix() {
    for(int x = 0; x < MAXX; x++) {
        for(int y = 0; y < MAXY; y++) {
            // randomly change characters -- even invisible ones
            if(rand01() < PROB_CHANGE || matrix[x][y].char_value == 0)
                matrix[x][y].char_value = RANDOM_PRINTABLE_CHARACTER;
            // randomly dim the cells
            if(rand01() < PROB_DIM && matrix[x][y].intensity > MIN_INTENSITY)
                matrix[x][y].intensity--;
        }
    }
}

void try_add_drips() {
    for(int i = 0; i < NUM_DRIPS; i++) {
        if(!drips[i].live) {
            drips[i].live = true;
            drips[i].x = rand() % MAXX;
            drips[i].y = 0;
            drips[i].bright = rand() % 2;
            return;
        }
    }
}

void update_drips() {
    for(int i = 0; i < NUM_DRIPS; i++) {
        if(drips[i].live) {
            if(drips[i].bright)
                matrix[drips[i].x][drips[i].y].intensity = MAX_INTENSITY;
            else
                matrix[drips[i].x][drips[i].y].intensity = MIN_INTENSITY;
            // drips die when they leave the screen
            if (++ drips[i].y >= MAXY-1) drips[i].live = false;
        }
    }
}

void matrix_update() {
    if(rand01() < PROB_DRIP_SPAWN) try_add_drips();
    update_drips();
    fade_n_change_matrix();
}