donut.c/doughnut.c

#include <math.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#if defined(_WIN32)
#define WIN32_LEAN_AND_MEAN
#define VC_EXTRALEAN
#include <Windows.h>
#define STEP_ROT_X 0.1488
#define STEP_ROT_Y 0.0768
#define STEP_THETA 0.126
#define STEP_PHI 0.063
#elif defined(__linux__)
#include <sys/ioctl.h>
#include <unistd.h>
#define STEP_ROT_X 0.0093
#define STEP_ROT_Y 0.0048
#define STEP_THETA 0.031
#define STEP_PHI 0.016
#endif

// Clears the terminal
void clear_terminal() {
#if defined(_WIN32)
    HANDLE hOut;
    COORD Position;
    hOut = GetStdHandle(STD_OUTPUT_HANDLE);
    Position.X = 0;
    Position.Y = 0;
    SetConsoleCursorPosition(hOut, Position);
#elif defined(__linux__)
    printf("\e[1;1H\e[2J");
#endif
}

// Function allocates memory for the frame buffer
char **allocate_memory(int size) {
    char **array = malloc(size * sizeof(char *));
    for (int i = 0; i < size; ++i)
        array[i] = malloc(size * sizeof(char));

    return array;
}

// Function gets the size of the terminal
int terminal_size() {
    int size;
#if defined(_WIN32)
    CONSOLE_SCREEN_BUFFER_INFO c;
    GetConsoleScreenBufferInfo(GetStdHandle(STD_OUTPUT_HANDLE), &c);
    int row = (int)(c.srWindow.Bottom - c.srWindow.Top + 1);
    int col = (int)(c.srWindow.Right - c.srWindow.Left + 1);
    size = row < col ? row : col;
#elif defined(__linux__)
    struct winsize w;
    ioctl(STDOUT_FILENO, TIOCGWINSZ, &w);
    size = w.ws_row < w.ws_col ? (int)w.ws_row : (int)w.ws_col;
#endif
    return size;
}

// Function dumps the frame into the terminal
void dump_frame(char **frame, int size) {
    for (int i = 0; i < size; ++i) {
        for (int j = 0; j < size; ++j)
            putchar(frame[i][j]);
        putchar('\n');
    }
}

// Function builds the frame and returns the frame buffer
char **build_frame(char **frame, int size, int frmno, int k) {
    float x = frmno * STEP_ROT_X; // Rotational speed around the x axis
    float y = frmno * STEP_ROT_Y; // Rotational speed around the y axis

    float cos_x = cos(x), sin_x = sin(x); // Precomputing sines and cosines of x
    float cos_y = cos(y), sin_y = sin(y); // Precomputing sines and cosines of y

    float z_buffer[size][size]; // Declaring buffer for storing z coordinates

    // Initializing frame buffer and z buffer
    for (int i = 0; i < size; ++i)
        for (int j = 0; j < size; ++j) {
            frame[i][j] = ' ';
            z_buffer[i][j] = 0;
        }

    // Loop uses theta to revolve a point around the center of the circle
    // 6.283186 = 2 * Pi = 360°
    for (float theta = 0; theta < 6.283186; theta += STEP_THETA) {
        // Precomputing sines and cosines of theta
        float cos_theta = cos(theta), sin_theta = sin(theta);

        // Loop uses phi to revolve the circle around the center of the torus
        for (float phi = 0; phi < 6.283186; phi += STEP_PHI) {
            // Precomputing sines and cosines of phi
            float cos_phi = cos(phi), sin_phi = sin(phi);

            // Calculating the x and y coordinates of the circle before the
            // revolution
            float circle_x = 2 + 1 * cos_theta, circle_y = 1 * sin_theta;

            // Calculating the x and y coordinates after the revolution
            float x = circle_x * (cos_y * cos_phi + sin_x * sin_y * sin_phi) -
                      circle_y * cos_x * sin_y;
            float y = circle_x * (sin_y * cos_phi - sin_x * cos_y * sin_phi) +
                      circle_y * cos_x * cos_y;

            // Calculating z
            float z = 5 + cos_x * circle_x * sin_phi + circle_y * sin_x;

            // Calculating the inverse of z
            float z_inv = 1 / z;

            // Calculating x and y coordinates of the 2D projection
            int x_proj = size / 2 + k * z_inv * x;
            int y_proj = size / 2 - k * z_inv * y;

            // Calculating luminous intensity
            float lumi_int =
                cos_phi * cos_theta * sin_y - cos_x * cos_theta * sin_phi -
                sin_x * sin_theta +
                cos_y * (cos_x * sin_theta - cos_theta * sin_x * sin_phi);

            /* Checking if surface is pointing away from the point of view
             * Also checking if the point is closer than any other point
             * previously plotted
             */
            if (lumi_int > 0 && z_inv > z_buffer[x_proj][y_proj]) {
                z_buffer[x_proj][y_proj] = z_inv;

                // Bringing the value of luminance between 0 to 11
                int lumi_idx = lumi_int * 8;

                /* Storing an appropriate character that represents the correct
                 * amount of luminance
                 */
                frame[x_proj][y_proj] = ".,-~:;=!*#$@"[lumi_idx];
            }
        }
    }

    // Returning the frame buffer
    return frame;
}

int main() {
    // Getting the size of the terminal
    const int size = terminal_size();

    // Allocating memory to the frame buffer
    char **frame = allocate_memory(size);

    // Loop rotates the torus around both the axes
    for (int frmno = 0; true; frmno++) {

        // Building and dumping the frame into the terminal
        int k = size * 5 * 3 / (8 * (1 + 2));
        dump_frame(build_frame(frame, size, frmno, k), size);

        // Clears the screen
        clear_terminal();
    }

    return 0;
}