Explaining donut like ears old Part-Last)

The complete code for C is

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

typedef struct {
    double a1;
    double a2;
    double a3;
} singleRow;

typedef struct {
    singleRow a1;
    singleRow a2;
    singleRow a3;
} Matrix;

singleRow multiply(singleRow m1, Matrix m2) {
    singleRow res;
    res.a1 = m1.a1 * m2.a1.a1 + m1.a2 * m2.a2.a1 + m1.a3 * m2.a3.a1;
    res.a2 = m1.a1 * m2.a1.a2 + m1.a2 * m2.a2.a2 + m1.a3 * m2.a3.a2;
    res.a3 = m1.a1 * m2.a1.a3 + m1.a2 * m2.a2.a3 + m1.a3 * m2.a3.a3;
    return res;
}

int main() {
  int screen_width = 80, height = 22;
  char buffer[1760];
  float zBuffer[1760];
  float A = 0, B = 0;
  int R2 = 2, R1 = 1;
  printf("\x1b[2J");
  while (1) {
    memset(buffer, ' ', 1760);
    memset(zBuffer, 0, 7040);
      for (float theta = 0; theta < 6.28; theta += 0.07) {
        for (float phi = 0; phi < 6.28; phi += 0.02) {
          singleRow circle = {2 + cos(theta), sin(theta), 0};
          // rotation on Y-axis
          Matrix Ry = {{cos(phi), 0, sin(phi)}, {0, 1, 0}, {-sin(phi), 0, cos(phi)}};
          // rotation on X-axis
          Matrix Rx = {{1, 0, 0}, {0, cos(A), sin(A)}, {0, -sin(A), cos(A)}};
          // rotation on Z-axis
          Matrix Rz = {{cos(B), sin(B), 0}, {-sin(B), cos(B), 0}, {0, 0, 1}};

          singleRow donut = multiply(circle, Ry);
          singleRow rotateX = multiply(donut, Rx);
          // We will consider it as [Nx, Ny, Nz]
          singleRow spinningDonut = multiply(rotateX, Rz);
          float reciNz = 1 / (spinningDonut.a3 + 5);

          int x = 40 + 30 * spinningDonut.a1 * reciNz;
          int y = 12 + 15 * spinningDonut.a2 * reciNz;

          // o is index of current buffer
          int o = x + screen_width * y;

          int L = 8 * (spinningDonut.a2 - spinningDonut.a3 + 2 * cos(B) * sin(A) * sin(phi)
            - 2 * cos(phi) * cos(theta) * sin(B)
            - 2 * cos(phi) * sin(B)
            + 2 * cos(A) * sin(phi)
          );

          // donut luminicity will be seen by these characters
          // these 12
          char charOut[] = ".,-~:;=!*#$@";

          if (x < screen_width && y < height && zBuffer[o] < reciNz) {
            zBuffer[o] = reciNz;
            // If L < 0, . will be buffer
            buffer[o] = charOut[L > 0 ? L : 0];
          }
        }
      }
    // Clear screen
    printf("\x1b[H");
    for (int i = 0; i <1761; i++) {
      // On every 80th character, new line will be printed
      // If there's a reminder then buffer printed
      putchar(i % 80 ? buffer[i] : 10);
      A += 0.00004;
      B += 0.00002;
    }
    // Timer to slow down speed a bit
    usleep(10000);
  }
  return 0;
}

The complete code for Java is

import java.util.Arrays;

class singleRow {
  public double a1;
  public double a2;
  public double a3;
  public singleRow(double a1, double a2, double a3) {
    this.a1 = a1;
    this.a2 = a2;
    this.a3 = a3;
  }
}
class Matrix {
  public singleRow a1;
  public singleRow a2;
  public singleRow a3;
  public Matrix(singleRow a1, singleRow a2, singleRow a3) {
    this.a1 = new singleRow(a1.a1, a1.a2, a1.a3);
    this.a2 = new singleRow(a2.a1, a2.a2, a2.a3);
    this.a3 = new singleRow(a3.a1, a3.a2, a3.a3);
  }
  public static singleRow multiply(singleRow m1, Matrix m2) {
    singleRow res = new singleRow(0, 0, 0);
    res.a1 = (m1.a1 * m2.a1.a1) + (m1.a2 * m2.a2.a1) + (m1.a3 * m2.a3.a1);
    res.a2 = (m1.a1 * m2.a1.a2) + (m1.a2 * m2.a2.a2) + (m1.a3 * m2.a3.a2);
    res.a3 = (m1.a1 * m2.a1.a3) + (m1.a2 * m2.a2.a3) + (m1.a3 * m2.a3.a3);
    return res;
  }
}


public class Main {
public static void main() {
  int screen_width = 80, height = 22;
  char[] buffer = new char[1760];
  double[] zBuffer = new double[1760];
  double A = 0, B = 0;
  int R2 = 2, R1 = 1;
  System.out.print("\u001b[2J");
  while (true) {
    Arrays.fill(buffer, 0, 1760, ' ');
    Arrays.fill(zBuffer, 0, 1760, 0);
      for (float theta = 0; theta < 6.28; theta += 0.07) {
        for (float phi = 0; phi < 6.28; phi += 0.02) {
          singleRow circle = {2 + Math.cos(theta), Math.sin(theta), 0};
          // rotation on Y-axis
          Matrix Ry = new Matrix(
          new singleRow(Math.cos(phi), 0, Math.sin(phi)),
          new singleRow(0, 1, 0),
          new singleRow(-Math.sin(phi), 0, Math.cos(phi))
        );
        // rotation on X-axis
        Matrix Rx = new Matrix(
          new singleRow(1, 0, 0),
          new singleRow(0, Math.cos(A), Math.sin(A)),
          new singleRow(0, -Math.sin(A), Math.cos(A))
        );
        // rotation on Z-axis
        Matrix Rz = new Matrix(
          new singleRow(Math.cos(B), Math.sin(B), 0),
          new singleRow(-Math.sin(B), Math.cos(B), 0),
          new singleRow(0, 0, 1)
        );

          singleRow donut = Matrix.multiply(circle, Ry);
          singleRow rotateX = Matrix.multiply(donut, Rx);
          // We will consider it as [Nx, Ny, Nz]
          singleRow spinningDonut = Matrix.multiply(rotateX, Rz);
          float reciNz = 1 / (spinningDonut.a3 + 5);

          int x = 40 + 30 * spinningDonut.a1 * reciNz;
          int y = 12 + 15 * spinningDonut.a2 * reciNz;

          // o is index of current buffer
          int o = x + screen_width * y;

          int L = 8 * (spinningDonut.a2 - spinningDonut.a3 
            + 2 * Math.cos(B) * Math.sin(A) * Math.sin(phi)
            - 2 * Math.cos(phi) * Math.cos(theta) * Math.sin(B)
            - 2 * Math.cos(phi) * Math.sin(B)
            + 2 * Math.cos(A) * Math.sin(phi)
          );

          // donut luminicity will be seen by these characters
          // these 12
          char[] charOpts = {'.', ',', '-', '~', ':', ';', '=', '!', '*', '#', '$', '@'};

          if (x < screen_width && y < height && zBuffer[o] < reciNz) {
            zBuffer[o] = reciNz;
            // If L < 0, . will be buffer
            buffer[o] = charOut[L > 0 ? L : 0];
          }
        }
      }
    // Clear screen
    System.out.print("\u001b[H");
    for (int i = 0; i <1761; i++) {
      // On every 80th character, new line will be printed
      // If there's a reminder then buffer printed
      System.out.print(i % 80 ? buffer[i] : 10);
      A += 0.00004;
      B += 0.00002;
    }
  }
}
}

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