/*

This program gives a basic introduction to "designs and mathematics"

*/

# include <math.h>
# include <stdlib.h>
# include <GL/glut.h>


const float pi = 22.0f/7.0f;


void DrawSineWave(void)
{
    int loop;
    const int samples = 45;
    const float amplitude = 20.0f;
    const float wavelength = 250.0f;
    const float dTheta = 2.0f*pi/samples;   
    float theta = -pi; 

    glBegin(GL_LINE_STRIP);
    for(loop = 0; loop <= samples; loop++)
    {
        float x = (theta/pi)*wavelength*0.5f;
        float y = amplitude*sinf(theta);

        theta += dTheta;
        
        glVertex2f(x, y);
    }
    glEnd();
}


void DrawEllipseAt(float x, float y, float a, float b)
{
    const int samples = 10;
    const float dTheta = 2.0f*pi/samples;
    float theta = 0.0f;
    int loop;

    a *= 1.5f;
    b *= 1.2f;

    glBegin(GL_LINE_STRIP);
    for(loop = 0; loop <= samples; loop++)
    {
        float x1 = x + a*cosf(theta);
        float y1 = y + b*sinf(theta);
        
        glVertex2f(x1, y1);
        theta += dTheta;
    }
    glEnd();
}


void DrawRing(float x, float y, float a, float b)
{
    int loop;
    const int samples = 14;
    const float dTheta = 2.0f*pi/samples;
    float theta = 0.0f;

    for(loop = 0; loop <= samples; loop++)
    {
        float x1 = x + a * cosf(theta);
        float y1 = y + b * sinf(theta);

        DrawEllipseAt(x1, y1, a, b);
        theta += dTheta;
    }
}


void Draw4CirclesAt(float x, float y)
{
    glColor3f(0.4f, 0.4f, 1.0f);
    DrawEllipseAt(x, y + 3.0f, 2.0f, 2.0f);
    DrawEllipseAt(x, y - 3.0f, 2.0f, 2.0f);
    DrawEllipseAt(x + 5.0f, y, 3.0f, 2.0f);
    DrawEllipseAt(x - 5.0f, y, 3.0f, 2.0f);

    glColor3f(1.0f, 0.1f, 0.1f);
    DrawEllipseAt(x, y + 3.0f, 3.0f, 3.0f);
    DrawEllipseAt(x, y - 3.0f, 3.0f, 3.0f);
    DrawEllipseAt(x + 5.0f, y, 4.0f, 3.0f);
    DrawEllipseAt(x - 5.0f, y, 4.0f, 3.0f);

}



void Draw(void)
{
    //            r    g    b    a
    glClearColor(0.0, 0.0, 0.0, 0.0);
    glClear(GL_COLOR_BUFFER_BIT);

    glColor3f(0.9f, 0.9f, 0.0f);
    DrawSineWave();
    glColor3f(0.0f, 1.0f, 0.0f);
    DrawRing(0.0f, 0.0f, 15.0f, 6.0f);
    
    DrawRing(35.0f, 15.0f, 6.0f, 4.0f);
    DrawRing(-35.0f, -15.0f, 6.0f, 4.0f);
    
    DrawRing(-60.0f, -20.0f, 4.0f, 2.0f);
    DrawRing(60.0f, 20.0f, 4.0f, 2.0f);
    
    Draw4CirclesAt(10.0f, 20.0f);
    Draw4CirclesAt(48.0f, 2.0f);

    Draw4CirclesAt(-10.0f, -20.0f);
    Draw4CirclesAt(-48.0f, -2.0f);


    glFlush();
}


void OnWindowResize(int width, int height)
{
    //See how the output changes if you change left and top
    int left = 0;
    int bottom = 0;

    glViewport(left, bottom, width, height);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();

    gluOrtho2D(-width/2.0, width/2.0, -height/2.0, height/2.0);
}


void OnKeyPress(unsigned char key, int x, int y)
{
# define ESC_Key 27

    switch (key)
    {
        case ESC_Key:
            exit(0);
        break;
    }

    //printf("\nThe mouse is @..(%d, %d)\n", x, y);
}


int main(int argc, char** argv)
{
    const int left = 0;
    const int top = 0;
    const int width = 512;
    const int height = 256;

    const char* windowTitle = "Hail Queen Mathematics!!!";

    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
    glutInitWindowSize(width, height); 
    glutInitWindowPosition(left, top);
    glutCreateWindow(windowTitle);
    
    glutDisplayFunc(Draw);
    glutReshapeFunc(OnWindowResize);
    glutKeyboardFunc(OnKeyPress);

    glutMainLoop();

    return 0;
}



/*
EXERCISE:
Show the output to your girl friend
and modify the design as she suggests
*/


//
//                MORAL of this tutorial
//               ~~~~~~~~~~~~~~~~~~~~~~~~
// If you are good at maths, you can play with curves ;)
//        (of course... PUN is always intended)
//