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


void RenderScene(void)
	{
	// Angle of revolution around the nucleus
	static float fElect1 = 0.0f;

	// Clear the window with current clearing color
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

	// Red Nucleus
	glColor3ub(255, 0, 0);
	glutSolidSphere(10.0f, 15, 15);

	// Yellow Electrons
	glColor3ub(255,255,0);

	// First Electron Orbit
	// Save viewing transformation
	glPushMatrix();
        glColor3f(1.0,1.0,0.0);

	// Rotate by angle of revolution
	glRotatef(fElect1, 0.0f, 1.0f, 0.0f);

	// Translate out from origin to orbit distance
	glTranslatef(90.0f, 0.0f, 0.0f);

	// Draw the electron
	glutSolidSphere(6.0f, 15, 15);

	// Restore the viewing transformation
	glPopMatrix();

	// Second Electron Orbit
	glPushMatrix();
        glColor3f(0.0,1.0,0.0);
	glRotatef(45.0f, 0.0f, 0.0f, 1.0f);
	glRotatef(fElect1, 0.0f, 1.0f, 0.0f);
	glTranslatef(-70.0f, 0.0f, 0.0f);
	glutSolidSphere(6.0f, 15, 15);
	glPopMatrix();


	// Third Electron Orbit
	glPushMatrix();
        glColor3f(0.0,0.0,1.0);
	glRotatef(360.0f-45.0f,0.0f, 0.0f, 1.0f);
	glRotatef(fElect1, 0.0f, 1.0f, 0.0f);
	glTranslatef(0.0f, 0.0f, 60.0f);
	glutSolidSphere(6.0f, 15, 15);
	glPopMatrix();


	// Increment the angle of revolution
	fElect1 += 10.0f;
	if(fElect1 > 360.0f)
		fElect1 = 0.0f;

	// Show the image
	glutSwapBuffers();
	}


// This function does any needed initialization on the rendering
// context. 
void SetupRC()
	{
	glEnable(GL_DEPTH_TEST);	// Hidden surface removal
	glEnable(GL_CULL_FACE);		// Do not calculate inside of jet
	glClearColor(0.0f, 0.0f, 0.0f, 1.0f );	
    }

void SpecialKeys(int key, int x, int y)
	{
	if(key == GLUT_KEY_UP)
		glutPostRedisplay();
	}

void ChangeSize(int w, int h)
    {
    GLfloat fAspect;

    // Prevent a divide by zero
    if(h == 0)
        h = 1;

    // Set Viewport to window dimensions
    glViewport(0, 0, w, h);

    // Reset coordinate system
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();

    fAspect = (float)w/(float)h;
    gluPerspective(45.0, fAspect, 1.0, 500.0);

    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    glTranslatef(0.0f, 0.0f, -250.0f);
    }

int main(int argc, char* argv[])
	{
	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
        glutInitWindowSize(800, 600);
	glutCreateWindow("OpenGL Atom - Perspective");
	glutReshapeFunc(ChangeSize);
	glutSpecialFunc(SpecialKeys);
	glutDisplayFunc(RenderScene);
	SetupRC();
	glutMainLoop();
	return 0;
	}