// Peter Bui
// CSE 40166 Computer Graphics (Fall 2010)
// Program 1: display initials in different colors
 
#include <math.h>
#include <stdlib.h>

#include <GL/glut.h>

void init();
void display();

int 
main(int argc, char *argv[])
{
    glutInit(&argc, argv);
    glutCreateWindow("initials"); 
    glutDisplayFunc(display);

    init(); // Setup some non-default parameters

    glutMainLoop();

    return (EXIT_SUCCESS);
}

void
init()
{
    // Choose a black background/clearing color
    glClearColor(0.0, 0.0, 0.0, 1.0);

    // Setup a non-perspective camera (more in later lectures/examples)
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(-10.0, 10.0, -10.0, 10.0, -10.0, 10.0);
}

void
draw_circle(GLfloat ox, GLfloat oy, GLfloat radius, int triangles)
{
    int i;
    GLfloat angle;

    glBegin(GL_TRIANGLE_FAN); {
	glVertex2f(ox, oy);
	for (i = 0; i <= triangles; i++) {
	    angle = i * 2.0 * M_PI / triangles;
	    glVertex2f(ox + radius * cos(angle), oy + radius * sin(angle));
	}
    } glEnd();
}

void
draw_semicircle(GLfloat ox, GLfloat oy, GLfloat radius, int triangles, int direction)
{
    int i;
    GLfloat angle;

    glBegin(GL_TRIANGLE_FAN); {
	glVertex2f(ox, oy);
	for (i = 0; i <= triangles; i++) {
	    angle = i * M_PI * direction / triangles;
	    glVertex2f(ox + radius * cos(angle), oy + radius * sin(angle));
	}
    } glEnd();
}

void 
display()
{
    glClear(GL_COLOR_BUFFER_BIT);

    // p
    glColor3f(1.0, 0.0, 0.0);
    glRectf(-6.0, 5.0, -5.0, -4.5);
    draw_circle(-3.5, 2.5, 2.5, 36);
    glColor3f(0.0, 0.0, 0.0);
    draw_circle(-3.5, 2.5, 1.5, 36);
    
    // j
    glColor3f(0.0, 1.0, 0.0);
    glRectf(-0.5, 5.0, 0.5, -2.5);
    draw_circle(0.0, 6.0, 0.5, 36);
    draw_semicircle(-2.0, -2.0, 2.5, 36, -1);
    glColor3f(0.0, 0.0, 0.0);
    draw_semicircle(-2.0, -2.0, 1.5, 36, -1);
    
    // b
    glColor3f(0.0, 0.0, 1.0);
    glRectf( 1.0, 9.5,  2.0, 0.0);
    draw_circle( 3.5, 2.5, 2.5, 36);
    glColor3f(0.0, 0.0, 0.0);
    draw_circle( 3.5, 2.5, 1.5, 36);

    glFlush();
}