/**
 * File glfractal.cpp
 * Brief Implementation of GLFractal
 * This is a simple QGLWidget displaying an openGL wireframe box
 *
 * The OpenGL code is mostly borrowed from Brian Pauls "spin" example
 * in the Mesa distribution.
 * $ID$
 */

#include "glfractal.h"

/**
 * Constructor that creates a GLFractal widget
 */
GLFractal::GLFractal( QWidget* parent, const char* name )
  : QGLWidget( parent, name )
{
   xRot = yRot = zRot = 0.0;
   scale = 1.25;
   object = 0;
}

GLFractal::~GLFractal()
{  glDeleteLists( object, 1 );
} // end destructor

/*--------------------------------------------------------------------------*/
/**
 * Paint the box. The actual openGL commands for drawing the box are
 * performed here.
 */
void GLFractal::paintGL()
{
  glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  glEnable( GL_DEPTH_TEST ); 
  glLoadIdentity();
  glTranslatef(0.0, 0.0, -10.0);
  // set the zoom according to the scale variable
  glScalef(scale, scale, scale);
  // set the image rotation up according to xRot, yRot, zRot
  glRotatef( xRot, 1.0, 0.0, 0.0);
  glRotatef( yRot, 0.0, 1.0, 0.0);
  glRotatef( zRot, 0.0, 0.0, 1.0);

  glCallList(object);
}

GLuint GLFractal::makeObject()
{  GLuint list;
   list = glGenLists(1);
   glNewList(list, GL_COMPILE);
     // set the initial color
     glColor3f( 1.0, 0.0, 0.0 );
     // points for triangle to draw Sierpinski Gasket
     Point a, b, c;
     a.x=-0.5; a.y=-0.5;
     b.x=0.5; b.y=-0.5;
     c.x=0.0; c.y=0.5;
     drawSierpinski(a,b,c,3);
   glEndList();
   return list;
} // end make object


/*--------------------------------------------------------------------------*/
/**
 * Set up the OpenGL rendering state, and define display list
 */

void GLFractal::initializeGL()
{
  glClearColor( 0.0, 0.0, 0.0, 0.0 ); // Let OpenGL clear to black
  object = makeObject(); // generate an OpenGL display list
  glShadeModel( GL_SMOOTH ); // we want smooth shading . . . try GL_FLAT if you like
}

/*--------------------------------------------------------------------------*/
/**
 * Set up the OpenGL view port, matrix mode, etc.
 */
void GLFractal::resizeGL( int w, int h )
{
  glViewport( 0, 0, (GLint)w, (GLint)h );
  glMatrixMode( GL_PROJECTION );
  glLoadIdentity();
  glFrustum(-1.0,1.0,-1.0,1.0,5.0,15.0);
  glMatrixMode( GL_MODELVIEW );
}

//*********************************************************
// Functions to rotate the model along the x, y, & z axes.
void GLFractal::setXRotation(int degrees)
{  xRot=(GLfloat)(degrees % 360);
   updateGL();
}

void GLFractal::setYRotation(int degrees)
{  yRot=(GLfloat)(degrees % 360);
   updateGL();
}

void GLFractal::setZRotation(int degrees)
{  zRot=(GLfloat)(degrees % 360);
   updateGL();
}

//**********************************************************
// Write Your Own Function To Set The Scale Here!!!!
//void GLFractal::setScale(int newscale){ }

//**********************************************************
// Draws a triangle
void GLFractal::drawTriangle(Point a, Point b, Point c)
{  glBegin(GL_POLYGON);
     glVertex2f(a.x,a.y);
     glVertex2f(b.x,b.y);
     glVertex2f(c.x,c.y);
   glEnd();
} // end draw triangle

//*******************************************************
// Function from class to draw the Sierpinski fractal
//   Recursion is FUN!
void GLFractal::drawSierpinski(Point a, Point b, Point c, int level)
{  Point m0, m1, m2;
	
   if (level > 0) {
     m0.x = (a.x+b.x) /2.0;
     m0.y = (a.y+b.y) /2.0;
     m1.x = (a.x+c.x) /2.0;
     m1.y = (a.y+c.y) /2.0;
     m2.x = (b.x+c.x) /2.0;
     m2.y = (c.y+b.y) /2.0;
     drawSierpinski(a,m0,m1,level-1);
     drawSierpinski(b,m2,m0,level-1);
     drawSierpinski(c,m1,m2,level-1);
   } else drawTriangle(a,b,c);
} // end draw Sierpinski