/* CPSC 360 Programming Assignment 4
 * 3-D Sierpinski Gasket
 * by Chris Bolduc
 * boldu101@chapman.edu
 */

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

#define DETAIL 2000000
#define WIDTH	20
#define HEIGHT	20
#define DEPTH	20
#define NUM_ITERATIONS 6
#define X 0
#define Y 1
#define Z 2
#define PI 3.1415926535897932384626433832795

// prototypes
void drawAxis();
void gasket2d();
void drawGasket2d(float g0[5][3], int iterations);
void gasket3d();

void init(){
	glClearColor(1.0, 1.0, 1.0, 0.0);
	glShadeModel(GL_FLAT);
	//gluOrtho2D(-WIDTH, WIDTH, -HEIGHT, HEIGHT);
}

// Displays an item
void displayItem(){
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	glLoadIdentity();
	gluLookAt(0.0, 0.0, 0.0, 0.0, 0.0, 25.0, 0.0, 1.0, 0.0);

	gasket3d();
	drawAxis();

	glFlush();
	glutSwapBuffers();
}

// Draws the XYZ axis
void drawAxis(){
	glBegin(GL_LINES);
		// x is red
		glColor3f(1, 0, 0);
		glVertex3f(-WIDTH, 0, 0);
		glVertex3f(WIDTH, 0, 0);
		// y is green
		glColor3f(0, 1, 0);
		glVertex3f(0, -HEIGHT, 0);
		glVertex3f(0, HEIGHT, 0);
		// z is blue
		glColor3f(0, 0, 1);
		glVertex3f(0, 0, -DEPTH);
		glVertex3f(0, 0, DEPTH);
	glEnd();
}

void gasket2d(){
	float g0[5][3];
	g0[1][X] = -WIDTH;
	g0[1][Y] = -HEIGHT;
	g0[2][X] = 0;
	g0[2][Y] = HEIGHT;
	g0[3][X] = WIDTH;
	g0[3][Y] = -HEIGHT;

	// Draw the solid triangle
	glColor3f(0.0, 0.0, 0.0);
	glBegin(GL_TRIANGLES);
		glVertex2f(g0[1][X], g0[1][Y]);
		glVertex2f(g0[2][X], g0[2][Y]);
		glVertex2f(g0[3][X], g0[3][Y]);
	glEnd();

	// Switch color to white and draw internal triangles
	glColor3f(1.0, 1.0, 1.0);
	drawGasket2d(g0, NUM_ITERATIONS);
}

// Draws the white triangles in the gasket
void drawGasket2d(float g0[5][3], int iterations){
	float g1[5][3], g2[5][3];
	int i;

	if(iterations == 0) return;

	// Remove the interior middle triangle
	g1[1][X] = (g0[1][X] + g0[2][X]) / 2;
	g1[2][X] = (g0[2][X] + g0[3][X]) / 2;
	g1[3][X] = (g0[1][X] + g0[3][X]) / 2;

	g1[1][Y] = (g0[1][Y] + g0[2][Y]) / 2;
	g1[2][Y] = (g0[2][Y] + g0[3][Y]) / 2;
	g1[3][Y] = (g0[1][Y] + g0[3][Y]) / 2;
	
	glBegin(GL_TRIANGLES);
		glVertex2f(g1[1][X], g1[1][Y]);
		glVertex2f(g1[2][X], g1[2][Y]);
		glVertex2f(g1[3][X], g1[3][Y]);
	glEnd();

	// Now draw the three other small triangles
	g2[1][X] = g0[1][X];
	g2[1][Y] = g0[1][Y];
	g2[2][X] = g1[1][X];
	g2[2][Y] = g1[1][Y];
	g2[3][X] = g1[3][X];
	g2[3][Y] = g1[3][Y];
	drawGasket2d(g2, iterations - 1);

	// We don't need g2 anymore, so we can use it again here
	g2[1][X] = g1[1][X];
	g2[1][Y] = g1[1][Y];
	g2[2][X] = g0[2][X];
	g2[2][Y] = g0[2][Y];
	g2[3][X] = g1[2][X];
	g2[3][Y] = g1[2][Y];
	drawGasket2d(g2, iterations - 1);

	g2[1][X] = g1[3][X];
	g2[1][Y] = g1[3][Y];
	g2[2][X] = g1[2][X];
	g2[2][Y] = g1[2][Y];
	g2[3][X] = g0[3][X];
	g2[3][Y] = g0[3][Y];
	drawGasket2d(g2, iterations - 1);
}

void gasket3d(){
	float p0[3] = { 2.0, -3.0, 5 };
	float p1[3];
	float v0[3] = { -WIDTH, -HEIGHT, 0 };
	float v1[3] = { 0, HEIGHT, 0 };
	float v2[3] = { WIDTH, -HEIGHT, 0 };
	float v3[3] = { 0, 0, DEPTH };
	int currVert = 0;
	int i;

	// Draw the solid triangle
	glColor3f(1.0, 0.0, 0.0);
	glBegin(GL_POINTS);
		glVertex3f(v0[0], v0[1], v0[2]);
		glVertex3f(v1[0], v1[1], v1[2]);
		glVertex3f(v2[0], v2[1], v2[2]);
		glVertex3f(v3[0], v3[1], v3[2]);
	glEnd();

	glColor3f(1.0, 0.0, 0.0);

	for(i = 0; i != DETAIL; ++i){
		switch(currVert){
		case 0:
			p1[0] = (p0[0] + v0[0]) / 2;
			p1[1] = (p0[1] + v0[1]) / 2;
			p1[2] = (p0[2] + v0[2]) / 2;
			break;
		case 1:
			p1[0] = (p0[0] + v1[0]) / 2;
			p1[1] = (p0[1] + v1[1]) / 2;
			p1[2] = (p0[2] + v1[2]) / 2;
			break;
		case 2:
			p1[0] = (p0[0] + v2[0]) / 2;
			p1[1] = (p0[1] + v2[1]) / 2;
			p1[2] = (p0[2] + v2[2]) / 2;
			break;
		case 3:
			p1[0] = (p0[0] + v3[0]) / 2;
			p1[1] = (p0[1] + v3[1]) / 2;
			p1[2] = (p0[2] + v3[2]) / 2;
			break;
		}
		glBegin(GL_POINTS);
			glVertex3f(p1[0], p1[1], p1[2]);
		glEnd();
		p0[0] = p1[0];
		p0[1] = p1[1];
		p0[2] = p1[2];
		currVert = rand() % 4;
	}
}

void winReshapeFcn(int newWidth, int newHeight){
	glViewport(0, 0, (GLsizei)newWidth, (GLsizei)newHeight);
	glDepthRange(0.0, 100.0);
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	glFrustum(-1.0, 1.0, -1.0, 1.0, 1.5, 25);
	glMatrixMode(GL_MODELVIEW);
}

int main(int argc, char *argv[]){
	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
	glutInitWindowPosition(50, 100);
	glutInitWindowSize(800, 600);
	glutCreateWindow("Example OpenGL Program");

	init();

	glutDisplayFunc(displayItem);
	glutReshapeFunc(winReshapeFcn);
	glutMainLoop();
	return 0;
}