// Computergraphik I
// Prof. Dr. Juergen Doellner
// Sommersemester 2001
// 
// Rahmenprogramm fuer Aufgabenzettel 8

#include "shape.h"

#include <iostream.h>
#include <GL/glut.h>

//
// Hilfsfunktionen
//

static inline double min(double a, double b) {
    return((a < b) ? a : b);
}

static inline double max(double a, double b) {
    return((a > b) ? a : b);
}

// Berechnet die Normale zum Dreieck. Die Dreieckseckpunkte muessen
// dazu im Gegenuhrzeigersinn angegeben werden.
static inline Vector normal(const Vector& p0, const Vector& p1, const Vector& p2) {
    // Verwende die ueberladenen Operatoren von Vector
    return((p1 - p0) * (p0 - p2));
}

//
// Triangle
//

Triangle::Triangle(const Vector& p0, const Vector& p1, const Vector& p2) {
    points_[0] = p0;
    points_[1] = p1;
    points_[2] = p2;
}

void Triangle::render() {
    glBegin(GL_TRIANGLES);
    glNormal3dv(normal(points_[0], points_[1], points_[2]).rep());
    glVertex3dv(points_[0].rep());
    glVertex3dv(points_[1].rep());
    glVertex3dv(points_[2].rep());
    glEnd();
}

//
// Box
//

Box::Box(const Vector& llf, const Vector& urb) {
    lowerLeftFront_ = Vector(min(llf[0], urb[0]),
                              min(llf[1], urb[1]),
                              min(llf[2], urb[2]));

    upperRightBack_ = Vector(max(llf[0], urb[0]),
                              max(llf[1], urb[1]),
                              max(llf[2], urb[2]));
}

void Box::render() {
	// damit das Tippen leichter fällt ...
#define l lowerLeftFront_
#define r upperRightBack_

	// oben
	Triangle oben1(Vector(l[0], r[1], l[2]), 
				   Vector(r[0], r[1], l[2]), 
				   Vector(r[0], r[1], r[2]));
	Triangle oben2(Vector(l[0], r[1], l[2]), 
				   Vector(r[0], r[1], r[2]), 
				   Vector(l[0], r[1], r[2]));
	oben1.render();
	oben2.render();

	// unten
	Triangle unten1(Vector(l[0], l[1], l[2]), 
				    Vector(r[0], l[1], l[2]), 
				    Vector(r[0], l[1], r[2]));
	Triangle unten2(Vector(l[0], l[1], l[2]), 
				    Vector(r[0], l[1], r[2]), 
				    Vector(l[0], l[1], r[2]));
	unten1.render();
	unten2.render();

	// hinten
	Triangle hinten1(Vector(l[0], l[1], r[2]), 
				     Vector(r[0], l[1], r[2]), 
				     Vector(r[0], r[1], r[2]));
	Triangle hinten2(Vector(l[0], l[1], r[2]), 
			   	     Vector(r[0], r[1], r[2]), 
			 	     Vector(l[0], r[1], r[2]));
	hinten1.render();
	hinten2.render();

	// vorn
	Triangle vorn1(Vector(l[0], l[1], l[2]), 
				   Vector(r[0], l[1], l[2]), 
				   Vector(r[0], r[1], l[2]));
	Triangle vorn2(Vector(l[0], l[1], l[2]), 
			   	   Vector(r[0], r[1], l[2]), 
			 	   Vector(l[0], r[1], l[2]));
	vorn1.render();
	vorn2.render();

	// links
	Triangle links1(Vector(l[0], l[1], l[2]), 
				    Vector(l[0], r[1], r[2]), 
				    Vector(l[0], l[1], r[2]));
	Triangle links2(Vector(l[0], l[1], l[2]), 
				    Vector(l[0], r[1], l[2]), 
				    Vector(l[0], r[1], r[2]));
	links1.render();
	links2.render();

	// rechts
	Triangle rechts1(Vector(r[0], l[1], l[2]), 
				     Vector(r[0], r[1], r[2]), 
				     Vector(r[0], l[1], r[2]));
	Triangle rechts2(Vector(r[0], l[1], l[2]), 
				     Vector(r[0], r[1], l[2]), 
				     Vector(r[0], r[1], r[2]));
	rechts1.render();
	rechts2.render();
#undef l
#undef r
}