/*
 * (c) Copyright 1993, Silicon Graphics, Inc.
 *               1993-1995 Microsoft Corporation
 *
 * ALL RIGHTS RESERVED
 *
 * Please refer to OpenGL/readme.txt for additional information
 *
 */

/*
 *  teaambient.c
 *  This program renders three lighted, shaded teapots, with
 *  different ambient values.
 */
#include "glos.h"

#include <GL/gl.h>
#include <GL/glu.h>
#include <GL/glaux.h>

void myinit(void);
void CALLBACK display(void);
void CALLBACK myReshape(GLsizei w, GLsizei h);

/*  Initialize light source and lighting model.
 */
void myinit(void)
{
    GLfloat light_ambient[] = { 0.0, 0.0, 0.0, 1.0 };
    GLfloat light_diffuse[] = { 1.0, 1.0, 1.0, 1.0 };
    GLfloat light_specular[] = { 1.0, 1.0, 1.0, 1.0 };
/*  light_position is NOT default value */
    GLfloat light_position[] = { 1.0, 0.0, 0.0, 0.0 };
    GLfloat global_ambient[] = { 0.75, 0.75, 0.75, 1.0 };

    glLightfv(GL_LIGHT0, GL_AMBIENT, light_ambient);
    glLightfv(GL_LIGHT0, GL_DIFFUSE, light_diffuse);
    glLightfv(GL_LIGHT0, GL_SPECULAR, light_specular);
    glLightfv(GL_LIGHT0, GL_POSITION, light_position);
    
    glLightModelfv(GL_LIGHT_MODEL_AMBIENT, global_ambient);
    
    glFrontFace (GL_CW);
    glEnable(GL_LIGHTING);
    glEnable(GL_LIGHT0);
    glEnable(GL_AUTO_NORMAL);
    glEnable(GL_NORMALIZE);
    glDepthFunc(GL_LESS);
    glEnable(GL_DEPTH_TEST);
}

void CALLBACK display(void)
{
    GLfloat low_ambient[] = { 0.1, 0.1, 0.1, 1.0 };
    GLfloat more_ambient[] = { 0.4, 0.4, 0.4, 1.0 };
    GLfloat most_ambient[] = { 1.0, 1.0, 1.0, 1.0 };

    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    /*  material has small ambient reflection   */
    glMaterialfv(GL_FRONT, GL_AMBIENT, low_ambient);
    glMaterialf(GL_FRONT, GL_SHININESS, 40.0);
    glPushMatrix ();
    glTranslatef (0.0, 2.0, 0.0);
    auxSolidTeapot(1.0);
    glPopMatrix ();

    /*  material has moderate ambient reflection    */
    glMaterialfv(GL_FRONT, GL_AMBIENT, more_ambient);
    glPushMatrix ();
    glTranslatef (0.0, 0.0, 0.0);
    auxSolidTeapot(1.0);
    glPopMatrix ();

    /*  material has large ambient reflection   */
    glMaterialfv(GL_FRONT, GL_AMBIENT, most_ambient);
    glPushMatrix ();
    glTranslatef (0.0, -2.0, 0.0);
    auxSolidTeapot(1.0);
    glPopMatrix ();
    glFlush();
}

void CALLBACK myReshape(GLsizei w, GLsizei h)
{
    h = (h == 0) ? 1 : h;
    glViewport(0, 0, w, h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    if (w <= h) 
    glOrtho (-4.0, 4.0, -4.0*(GLfloat)h/(GLfloat)w, 
        4.0*(GLfloat)h/(GLfloat)w, -10.0, 10.0);
    else 
    glOrtho (-4.0*(GLfloat)w/(GLfloat)h, 
        4.0*(GLfloat)w/(GLfloat)h, -4.0, 4.0, -10.0, 10.0);
    glMatrixMode(GL_MODELVIEW);
}

/*  Main Loop
 *  Open window with initial window size, title bar, 
 *  RGBA display mode, and handle input events.
 */
int main(int argc, char** argv)
{
    auxInitDisplayMode (AUX_SINGLE | AUX_RGB | AUX_DEPTH16);
    auxInitPosition (0, 0, 500, 500);
    auxInitWindow ("Ambient Lighting");
    myinit();
    auxReshapeFunc (myReshape);
    auxMainLoop(display);
    return(0);
}