//
// Computergraphik II
// Prof. Dr. Juergen Doellner
// Wintersemester 2001/02
// 
// Rahmenprogramm zu Aufgabenzettel 1
//

#include "cgtranslucent.h"
#include <fstream.h>
#include <stdlib.h>
#include <GL/glut.h>

CGTranslucent::CGTranslucent() {
    run_ = true;
	moveX_ = 0.0;
	dirX_ = 0.005;
}

CGTranslucent::~CGTranslucent( ) {    
}


void CGTranslucent::onInit() {
    // OpenGL Lichtquelle
    static GLfloat light_diffuse[] = {1.0, 1.0, 1.0, 1.0};  /* diffuse light. */
    static GLfloat light_position[] = {1.0, 1.0, 1.0, 0.0};  /* Infinite light location. */    
    glLightfv(GL_LIGHT0, GL_DIFFUSE, light_diffuse);
    glLightfv(GL_LIGHT0, GL_POSITION, light_position);
    glEnable(GL_LIGHTING);
    glEnable(GL_LIGHT0);
    
    // automatische Normalisierung
    glEnable(GL_NORMALIZE);
    
    glEnable(GL_COLOR_MATERIAL);
    glColorMaterial(GL_FRONT_AND_BACK,GL_AMBIENT_AND_DIFFUSE); 

    // Tiefen Test aktivieren
    glEnable(GL_DEPTH_TEST);
    
    // Smooth Schattierung aktivieren
    glShadeModel(GL_SMOOTH);
    
    // Projection
    glMatrixMode(GL_PROJECTION);
    gluPerspective(60.0,1.0,2,2000.0);   
    
    // LookAt
    glMatrixMode(GL_MODELVIEW);
    gluLookAt(0.0, 0.0, 4.0,  // from (0,0,4) 
	          0.0, 0.0, 0.0,  // to (0,0,0) 
			  0.0, 1.0, 0.);  // up
    
    glClearColor(1.0,1.0,1.0,1.0);
}
void CGTranslucent::onSize(unsigned int newWidth,unsigned int newHeight) {          
    width_ = newWidth;
    height_ = newHeight;            
    glMatrixMode(GL_PROJECTION);
    glViewport(0, 0, width_ - 1, height_ - 1);        
    glLoadIdentity();
    gluPerspective(40.0,float(width_)/float(height_),2.0, 100.0);
    glMatrixMode(GL_MODELVIEW);     
}

void CGTranslucent::onKey(unsigned char key) {
    switch (key) {
    case 27: { exit(0); break; }                        
    case ' ': { run_ = !run_; break; }
    }
    onDraw();
}

void CGTranslucent::onIdle() {  
	moveX_+= dirX_;
	if(moveX_ > 1.4) { 
		moveX_-=(dirX_); 
		dirX_ = -dirX_; 
	} else if(moveX_ < -1.4) {
		moveX_-=(dirX_);
		dirX_ = -dirX_; 
	}

    if (run_) {
        glRotatef(1,0.1,1,0.2);         
    }
    
	onDraw();
}

void CGTranslucent::onDraw() {
	// Mechanismus zur Behandlung opaker Objekte 
	glDepthMask(GL_TRUE);
	glDisable(GL_BLEND);

    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);                

	glColor4f(1,1,0,1); // nicht Transparent (A=1)
	glPushMatrix();
		glTranslatef(moveX_,0,0);
		glutSolidSphere(0.5, 32, 32);
	glPopMatrix();

	// Mechanismus zur Behandlung transparenter Objekte 
	glEnable(GL_BLEND);	
	glDepthMask(GL_FALSE);

	glColor4f(1,0,0,0.4); // Transparent (A=0.4)
	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
	glutSolidSphere(0.8, 32, 32);

    // Nicht vergessen! Front- und Back-Buffer tauschen:
    swapBuffers();
}

// Hauptprogramm
int main(int argc, char* argv[]) {
    // Erzeuge eine Instanz der Beispiel-Anwendung:
    CGTranslucent sample;
    
    // Starte die Beispiel-Anwendung:
    sample.start("CGTranslucent", true, 400, 400);
    return(0);
}