2D-Triangle-Rotating/triangle.cpp at main · Bernhard09/2D-Triangle-Rotating · GitHub

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#include <iostream>
#include <math.h>
#include <vector>
#include <unistd.h>

using namespace std;

void rotate(float& x, float& y, float theta);
void plot(float& x, float& y, vector<string>& area, const float& scale, const int& centerX, const int& centerY);

int main()
{
    // area dimension
    const int width = 80;
    const int height = 24;

    // center factor
    const int centerX = width/2;
    const int centerY = height/2;


    // scale factor
    const float scale = 7.5f;

    // rotation properties
    float theta = 0.0f;
    const float rotationSpeed = 0.05f;

    // create triangle
    const float range = 0.02f;

    // x and y cartesians points
    float x, y;

    while (1)
    {
        // area buffer
        vector<string> area(height, string(width, '.'));

        for (float i = 0.0f; i <= 1.0f; i+=range)
        {
            // bottom side
            x = -1.0f + 2.0f * i;
            y = -1.0f;
            rotate(x, y, theta);
            plot(x, y, area, scale, centerX, centerY);

            if (i <= 0.5)
            {
                // diagonal left-side
                x = -1.0f + 2.0f * i;
                y = 2 * x + 1; // bend the line
                rotate(x, y, theta);
                plot(x, y, area, scale, centerX, centerY);

                // diagonal right-side
                x = 1.0f - 2.0f * i;
                y = -2 * x + 1; // bend the line
                rotate(x, y, theta);
                plot(x, y, area, scale, centerX, centerY);
            }


        }


        for (auto &row : area)
        {
            cout << row << endl;
        }

        theta += rotationSpeed;

        // animation delay
        usleep(15000); // 2ms
    }


    return 0;
}

void plot(float& x, float& y, vector<string>& area, const float& scale, const int& centerX, const int& centerY)
{

    // convert (1, 1) ... (-1, -1) to (0, 0) ... (0, 0)
    const int screenX = static_cast<int>(centerX + (x * scale));
    const int screenY = static_cast<int>(centerY - (y * scale));

    // insert to buffer area
    if (screenX >= 0 && screenX < static_cast<int>(area[0].size()) && screenY >= 0 && screenY < static_cast<int>(area.size()))
    {
        area[screenY][screenX] = 'O';
    }

}

void rotate(float& x, float& y, float theta)
{
    float new_x, new_y;

    // rotate using matrix 2d-rotation
    new_x = x * cos(theta) - y * sin(theta);
    new_y = x * sin(theta) + y * cos(theta);

    // assign rotated value to x and y
    x = new_x;
    y = new_y;
}