/*
 * 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.
 */


/* solar5.c - a simple solar system.
 *
 *	F1 key			- print help information
 *	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 drawScene( GLvoid );

void printHelp( char * );

/* Global Variables */

static char *progname; 

static GLboolean filledFlag = GL_TRUE;

/* 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 );
	glutCreateWindow( argv[0] );

	initgfx();

	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"
		"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 );

	glMatrixMode( GL_PROJECTION );
	gluPerspective( 45.0f, 1.0f, 1.0f, 20.0f );
	glMatrixMode( GL_MODELVIEW );
}

GLvoid 
keyboard( GLubyte key, GLint x, GLint y )
{
	switch (key) {
	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
drawScene( GLvoid )
{
	static GLfloat	year = 45.0f, day = -90.0;

	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 );

	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( 0.7f, 15, 15 );
			else
				glutWireSphere( 0.7f, 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( 3.5f, 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( 0.4f, 15, 15 );
				else
					glutWireSphere( 0.4f, 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( 1.0f, 0.0f, 0.0f );

				/* rotate on our axis */
				glRotatef( 90.0f, 1.0f, 0.0f, 0.0f );
				if (filledFlag)
					glutSolidSphere( 0.2f, 15, 15 );
				else
					glutWireSphere( 0.2f, 15, 15 );

			glPopMatrix();

		glPopMatrix();

	glPopMatrix();

	checkError( "drawScene" );

	glFlush();
}