/*
 * Copyright (c) 1996-1999  Silicon Graphics, Inc.  All rights reserved.
 *
 * THE SOFTWARE IS PROVIDED "AS-IS" AND WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS, IMPLIED OR OTHERWISE, INCLUDING WITHOUT LIMITATION, ANY
 * WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
 *
 * IN NO EVENT SHALL SILICON GRAPHICS BE LIABLE FOR ANY SPECIAL, INCIDENTAL,
 * INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND, OR ANY DAMAGES WHATSOEVER
 * RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER OR NOT ADVISED OF THE
 * POSSIBILITY OF DAMAGE, AND ON ANY THEORY OF LIABILITY, ARISING OUT OF OR IN
 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

/* solar8.c - a simple solar system.  
 *	Added a reshape handler to reset the viewport and viewing volume.
 *	Add depth buffering and back face culling.
 * 	Add continuous animation and an option to toggle it on and off.
 *
 *	F1 key			- print help information
 *	<r> Key			- toggle rotation on / off
 *	SPACE Key		- toggle between solid/wireframe models
 *	Escape Key		- exit program
 */
#include <GL/glut.h>	/* includes gl.h, glu.h */

#include <stdio.h>
#include <math.h>

#include "checkerror.h"

/* Function Prototypes */

GLvoid initgfx( GLvoid );
GLvoid keyboard( GLubyte, GLint, GLint );
GLvoid specialkeys( GLint, GLint, GLint );
GLvoid animate( GLvoid );
GLvoid visibility( GLint );
GLvoid reshape( GLsizei, GLsizei );
GLvoid drawScene( GLvoid );

void printHelp( char * );

/* Global Variables */

static char *progname; 

static GLboolean filledFlag = GL_TRUE;

static GLfloat		sunRadius = 0.7f;
static GLfloat		earthRadius = 0.4f, earthOrbit = 3.5f; 
static GLfloat		moonRadius = 0.2f, moonOrbit = 1.0f;
static GLfloat 		nearClip, farClip, distance, twistAngle, incAngle, azimAngle;

static GLfloat		year = 45.0f, day = -90.0f;

/* Global Definitions */

#define KEY_ESC	27	/* ascii value for the escape key */

void
main( int argc, char *argv[] )
{
	GLsizei width, height;

	glutInit( &argc, argv );

	/* create a window that is 1/4 the size of the screen,
	 * and position it in the middle of the screen.
	 */
	width = glutGet( GLUT_SCREEN_WIDTH ); 
	height = glutGet( GLUT_SCREEN_HEIGHT );
	glutInitWindowPosition( width / 4, height / 4 );
	glutInitWindowSize( width / 2, height / 2 );
	glutInitDisplayMode( GLUT_RGBA | GLUT_DEPTH | GLUT_DOUBLE );
	glutCreateWindow( argv[0] );

	initgfx();

	glutIdleFunc( animate );
	glutVisibilityFunc( visibility );
	glutReshapeFunc( reshape );
	glutKeyboardFunc( keyboard );
	glutSpecialFunc( specialkeys );
	glutDisplayFunc( drawScene ); 

	progname = argv[0];

	printHelp( progname );

	glutMainLoop();
}

void
printHelp( char *progname )
{
	fprintf(stdout, 
		"\n%s - model the solar system\n\n"
		"F1 key		- print help information\n"
		"<r> Key		- toggle rotation on / off\n"
		"SPACE key	- toggle between solid/wireframe mode\n"
		"Escape Key	- exit the program\n\n",
		progname);
}

GLvoid
initgfx( GLvoid )
{
	/* set clear color to black */
	glClearColor( 0.0f, 0.0f, 0.0f, 1.0f );

	/* enable the depth buffer */
	glEnable( GL_DEPTH_TEST );

	/* enable the face culling */
	glEnable( GL_CULL_FACE );
}

GLvoid 
reshape( GLsizei width, GLsizei height )
{
	GLdouble    aspect;

	glViewport( 0, 0, width, height );

	/* compute aspect ratio */
	aspect = (GLdouble) width / (GLdouble) height;

	glMatrixMode( GL_PROJECTION );

	/* Reset world coordinates first ... */
	glLoadIdentity();

	/* Reset the viewing volume based on the new aspect ratio */
	gluPerspective( 45.0f, aspect, 1.0f, 20.0f );

	glMatrixMode( GL_MODELVIEW );
}

GLvoid 
keyboard( GLubyte key, GLint x, GLint y )
{
	static GLboolean	rotateFlag = GL_TRUE;

	switch (key) {
	case 'r':
		rotateFlag = !rotateFlag;
		if (rotateFlag) {
			glutIdleFunc( animate );
		} else {
			glutIdleFunc( NULL );
		}
		glutPostRedisplay();
		break;
	case ' ':	/* toggle fill mode */
		filledFlag = !filledFlag;
		glutPostRedisplay();
		break;
	case KEY_ESC:	/* Exit when the Escape key is pressed */
		exit(0);
	}
}

GLvoid 
specialkeys( GLint key, GLint x, GLint y )
{
	switch (key) {
	case GLUT_KEY_F1:	/* Function key #1 */
		/* print help information */
		printHelp( progname );
		break;
	}
}

GLvoid 
animate( GLvoid )
{
	/* update the rotation of the earth and moon in their orbits */
	year = fmod( (year + 0.5), 360.0f );
	day = fmod( (day + 5.0), 360.0f );

	/* Tell GLUT to redraw the scene */
	glutPostRedisplay();
}

GLvoid
visibility( int state ) 
{
	if (state == GLUT_VISIBLE) {
		glutIdleFunc( animate );
	} else {
		glutIdleFunc( NULL );
	}
}

GLvoid
drawScene( GLvoid )
{
	static GLfloat  yellow[] = { 1.0f, 1.0f, 0.0f, 1.0f };
	static GLfloat  blue[] = { 0.0f, 0.0f, 1.0f, 1.0f };
	static GLfloat  gray[] = { 0.2f, 0.2f, 0.2f, 1.0f };

	glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );

	glPushMatrix();

		/* move into the viewing volume */
		glTranslatef( 0.0f, 0.0f, -10.0f );

		/* draw sun */

		glPushMatrix();

		/* Give the sun a yellow glow */
			glColor4fv( yellow );
	  
			/* rotate on our own axis */
			glRotatef( 90.0f, 1.0f, 0.0f, 0.0f );
			if (filledFlag)
				glutSolidSphere( sunRadius, 15, 15 );
			else
				glutWireSphere( sunRadius, 15, 15 );

		glPopMatrix();

		glPushMatrix();

			/* draw earth */

			/* rotate to the right time of year */
			glRotatef( year, 0.0f, 1.0f, 0.0f );

			/* translate out to our orbit about the sun */
			glTranslatef( earthOrbit, 0.0f, 0.0f );
			glPushMatrix();

				/* set color for the earth */
				glColor4fv( blue );

				/* rotate on our own axis */
				glRotatef( 90.0f, 1.0f, 0.0f, 0.0f );
				if (filledFlag)
					glutSolidSphere( earthRadius, 15, 15 );
				else
					glutWireSphere( earthRadius, 15, 15 );

			glPopMatrix();

			/* draw moon */
			glPushMatrix();

				/* set color for the moon */
				glColor4fv( gray );

				/* rotate to the right time of day */
				glRotatef( day, 0.0f, 1.0f, 0.0f );

				/* translate out to our orbit about the earth */
				glTranslatef( moonOrbit, 0.0f, 0.0f );

				/* rotate on our axis */
				glRotatef( 90.0f, 1.0f, 0.0f, 0.0f );
				if (filledFlag)
					glutSolidSphere( moonRadius, 15, 15 );
				else
					glutWireSphere( moonRadius, 15, 15 );

		glPopMatrix();

		glPopMatrix();

	glPopMatrix();

	checkError( "drawScene" );

	glutSwapBuffers();
}