A 3D ASCII-Terminal cube projection.

ASCII-Cube.c

// gcc -o ASCII-Cube -O2 -DNDEBUG -Wall -Wextra -Werror ASCII-Cube.c -lm
// ./ASCII-Cube

// NOTE: - Resize the terminal to at least 160 columns & 44 rows.
//       - This does depend on a terminal which supports ASCII escape codes.

#include <stdbool.h>
#include <string.h>
#include <unistd.h>
#include <stdio.h>
#include <math.h>

#define CubeSize      10.f
#define BUFFER_WIDTH  160
#define BUFFER_HEIGHT 44

static float  ZBuffer[BUFFER_WIDTH*BUFFER_HEIGHT];
static char OutBuffer[BUFFER_WIDTH*BUFFER_HEIGHT];

static float A = 0.00f;
static float B = 0.00f;
static float C = 0.00f;

static float CalculateX(int i, int j, int k)
{
    return j * sin(A) * sin(B) * cos(C) -
           k * cos(A) * sin(B) * cos(C) +
           j * cos(A) * sin(C) +
           k * sin(A) * sin(C) +
           i * cos(B) * cos(C);
}

static float CalculateY(int i, int j, int k)
{
    return j * cos(A) * cos(C) +
           k * sin(A) * cos(C) -
           j * sin(A) * sin(B) * sin(C) +
           k * cos(A) * sin(B) * sin(C) -
           i * cos(B) * sin(C);
}

static float CalculateZ(int i, int j, int k)
{
    return k * cos(A) * cos(B) -
           j * sin(A) * cos(B) +
           i * sin(B);
}

static void ProjectSurface(float cx, float cy, float cz, char character)
{
    float x = CalculateX(cx, cy, cz);
    float y = CalculateY(cx, cy, cz);
    float z = CalculateZ(cx, cy, cz) + BUFFER_HEIGHT - CubeSize;

    float zOff = 40;
    float invZ = 1/z;
    float xOff = CubeSize*2;

    int xp = (int)(BUFFER_WIDTH/2  + zOff * invZ * x * 2 - xOff);
    int yp = (int)(BUFFER_HEIGHT/2 + zOff * invZ * y);
    unsigned int index = xp + yp * BUFFER_WIDTH;

    if (index < sizeof(OutBuffer))
        if (ZBuffer[index] < invZ)
        {
            ZBuffer[index] = invZ;
            OutBuffer[index] = character;
        }
}

int main()
{
    printf("\x1b[2J");
    while (true)
    {
        memset(OutBuffer, ' ', sizeof(OutBuffer));
        memset(ZBuffer,   0x0, sizeof(ZBuffer));

        for (float x = -CubeSize; x < CubeSize; x++)
            for (float y = -CubeSize; y < CubeSize; y++)
            {
                ProjectSurface( x,        y,        -CubeSize, '.');
                ProjectSurface( CubeSize, y,         x,        '$');
                ProjectSurface(-CubeSize, y,        -x,        '~');
                ProjectSurface(-x,        y,         CubeSize, '@');
                ProjectSurface( x,       -CubeSize, -y,        ';');
            }

        printf("\x1b[H");
        for (unsigned int i = 0; i < sizeof(OutBuffer); i++)
            putchar(i % BUFFER_WIDTH ? OutBuffer[i] : '\n');
        
        A += 0.005f;
        B += 0.005f;
        usleep(2000);
    }
}