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

/*
 *  movelight.c
 *  This program demonstrates when to issue lighting and 
 *  transformation commands to render a model with a light 
 *  which is moved by a modeling transformation (rotate or 
 *  translate).  The light position is reset after the modeling 
 *  transformation is called.  The eye position does not change.
 *
 *  A sphere is drawn using a grey material characteristic. 
 *  A single light source illuminates the object.
 *
 *  Interaction:  pressing the left or middle mouse button
 *  alters the modeling transformation (x rotation) by 30 degrees.  
 *  The scene is then redrawn with the light in a new position.
 */
#include "glos.h"

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

void myinit(void);
void CALLBACK movelight (AUX_EVENTREC *event);
void CALLBACK display(void);
void CALLBACK myReshape(GLsizei w, GLsizei h);

static int spin = 0;

void CALLBACK movelight (AUX_EVENTREC *event)
{
    spin = (spin + 30) % 360;
}

void myinit (void)
{
    glEnable(GL_LIGHTING);
    glEnable(GL_LIGHT0);

    glDepthFunc(GL_LESS);
    glEnable(GL_DEPTH_TEST);
}

/*  Here is where the light position is reset after the modeling
 *  transformation (glRotated) is called.  This places the 
 *  light at a new position in world coordinates.  The cube
 *  represents the position of the light.
 */
void CALLBACK display(void)
{
    GLfloat position[] = { 0.0, 0.0, 1.5, 1.0 };

    glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glPushMatrix ();
    glTranslatef (0.0, 0.0, -5.0); 

    glPushMatrix ();
    glRotated ((GLdouble) spin, 1.0, 0.0, 0.0);
    glRotated (0.0, 1.0, 0.0, 0.0);
    glLightfv (GL_LIGHT0, GL_POSITION, position);

    glTranslated (0.0, 0.0, 1.5);
    glDisable (GL_LIGHTING);
    glColor3f (0.0, 1.0, 1.0);
    auxWireCube (0.1);
    glEnable (GL_LIGHTING);
    glPopMatrix ();

    auxSolidTorus (0.275, 0.85);
    glPopMatrix ();
    glFlush ();
}

void CALLBACK myReshape(GLsizei w, GLsizei h)
{
    h = (h == 0) ? 1 : h;
    glViewport(0, 0, w, h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective(40.0, (GLfloat) w/(GLfloat) h, 1.0, 20.0);
    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 ("Moving Light");
    myinit();
    auxMouseFunc (AUX_LEFTBUTTON, AUX_MOUSEDOWN, movelight);
    auxReshapeFunc (myReshape);
    auxMainLoop(display);
    return(0);
}
