package classwork;

import javax.media.opengl.*;
import jocode.*;

/**
 * GLART_2_orbit.java
 *
 * Three cubes simulate a very basic solar system, with a rotating sun
 * and orbiting earth and mars.
 */
public class GLART_2_orbit  extends JOApp {
 	float rotation = 0f;
 	int marbleTextureHandle;

    /**
     * Main function just creates and runs the application.
     */
    public static void main(String args[]) {
    	GLART_2_orbit app = new GLART_2_orbit();
        app.run();
    }

    /**
     * Initialize the scene.  Called by JOApp.run()
     */
    public void setup() {
        // Create sphere texture
        marbleTextureHandle = makeTexture("images/marble.jpg");

        // enable texture (or call JOApp.activateTexture(handle))
        gl.glBindTexture(GL.GL_TEXTURE_2D, marbleTextureHandle);

        // enable texture rendering
        gl.glEnable(GL.GL_TEXTURE_2D);
        
        // enable depth test
        gl.glEnable(GL.GL_DEPTH_TEST);
    }

    /**
     * Render the scene.
     */
    public void draw() {
     	rotation += .5f;

        // Clear screen and depth buffer
        gl.glClear(GL.GL_COLOR_BUFFER_BIT | GL.GL_DEPTH_BUFFER_BIT);

        // Select The Modelview Matrix (controls model orientation)
        gl.glMatrixMode(GL.GL_MODELVIEW);

        // Reset the Modelview matrix
        // this resets the coordinate system to center of screen
        gl.glLoadIdentity();

        // Where is the 'eye'
        glu.gluLookAt(
            0f, 1f, 5f,    // eye position
            0f, 0f, 0f,    // target to look at
            0f, 1f, 0f);   // which way is up

        // draw crosshairs
        drawOrigin();

        // draw large yellow sphere at center, turning slowly on its axis
		gl.glColor3f(1f,1f,0f);
        gl.glPushMatrix();
		{
			gl.glRotatef(rotation/5f, 0, 1, 0);
			gl.glScalef(.6f, .6f, .6f);
			renderSphere();
		}
        gl.glPopMatrix();

		// draw orbiting green sphere
        // ?? what happens if you don't use PushMatrix/PopMatrix here?
        gl.glPushMatrix();
		{
			// rotate coord system (so earth orbits sun)
			gl.glRotatef(rotation * .5f, 0, 1, 0);
			// shift coordinate system right
			gl.glTranslatef(2, 0, 0);
			// rotate coord system (to spin earth)
			gl.glRotatef(rotation * .3f, 0, 1, 0);
			// shrink it down
			gl.glScalef(.3f, .3f, .3f);
			// draw a green sphere
			gl.glColor3f(.3f,.9f,0);
			renderSphere();
		}
	    gl.glPopMatrix();

	    // draw orbiting red sphere
	    gl.glPushMatrix();
	    {
	    	// rotate (so mars orbits sun)
	    	gl.glRotatef(rotation, 0, 1, 0);
	    	// shift coordinate system right
	    	gl.glTranslatef(3, 0, 0);
	    	// rotate coord system (to spin mars)
	    	gl.glRotatef(rotation * 3f, 0, 1, 0);
	    	// shrink
	    	gl.glScalef(.2f, .2f, .2f);
	    	// draw a cube
	    	gl.glColor3f(.9f,.3f,0f);
	    	renderSphere();
	    }
	    gl.glPopMatrix();
    }

    /**
     * Draw crosshairs at 0,0,0
     */
    public void drawOrigin() {
    	gl.glColor3f(.5f, .5f, .5f);
        gl.glLineWidth(1);
        gl.glBegin(GL.GL_LINES);
	    	gl.glVertex3f( -1f, 0f, 0f);        // left
	    	gl.glVertex3f( 1f, 0f, 0f);         // right

	    	gl.glVertex3f( 0f, -1f, 0f);        // bottom
	    	gl.glVertex3f( 0f, 1f, 0f);         // top

			gl.glVertex3f( 0f, 0f, -1f);        // far
			gl.glVertex3f( 0f, 0f, 1f);         // near
		gl.glEnd();
		gl.glBegin(GL.GL_LINE_STRIP);
			gl.glVertex3f( -1f, 0f, 1f);        // left near
			gl.glVertex3f( 1f, 0f, 1f);         // rite near
			gl.glVertex3f( 1f, 0f, -1f);        // rite far
			gl.glVertex3f( -1f, 0f, -1f);       // left far
			gl.glVertex3f( -1f, 0f, 1f);        // left near (close)
		gl.glEnd();
    }
}