#include"glut.h"
#include"math.h"

#define RADIUS 500
#define PI 3.141592654f
#define R 10.0f

#define Y_GROUND -3.0f
#define F_EXTENT 70.0f
#define F_STEP 5.0f

GLfloat Rot = 0.0f;
GLint mx = 0 , my = 0;
GLint mz = -RADIUS;
GLfloat keyStep = 0.5f;

GLfloat lightPos[] = { -20 , 30 , -10 , 1 };
GLfloat spotDir[] = { 50 , -200 , 50 };
GLfloat specular[] = { 1 , 1 , 1 , 1 };
GLfloat specref[] = { 1 , 1 , 1 , 1 };
GLfloat ambientLight[] = { 0.5 , 0.5 , 0.5 , 1 };

//void MyTimer( int value )
//{
// if( abs(Rot) >= 60 )
//  step *= -1;
// Rot += step;
// glutPostRedisplay();
// glutTimerFunc( 100 , MyTimer , 0 );
//}

void init()
{
 glEnable( GL_DEPTH_TEST );
 glEnable( GL_BLEND );
 /*glFrontFace( GL_CCW );
 glEnable( GL_CULL_FACE );*/

 glEnable( GL_LIGHTING );
 glLightModelfv( GL_LIGHT_MODEL_AMBIENT , ambientLight );//定义一个全局光源，让所有物体都能够被看见
 glLightfv( GL_LIGHT0 , GL_DIFFUSE , ambientLight );
 glLightfv( GL_LIGHT0 , GL_SPECULAR , specular );
 glLightfv( GL_LIGHT0 , GL_POSITION , lightPos );
 //glLightfv( GL_LIGHT0 , GL_SPOT_DIRECTION , spotDir );
 //glLightf( GL_LIGHT0 , GL_SPOT_CUTOFF , 90.0f );//光源点的cutoff角
 glEnable( GL_LIGHT0 );

 glEnable( GL_COLOR_MATERIAL );
 glColorMaterial( GL_FRONT , GL_AMBIENT_AND_DIFFUSE );
 glMaterialfv( GL_FRONT , GL_SPECULAR , specular );
 glMateriali( GL_FRONT , GL_SHININESS , 180 );

 glClearColor( 0.0f , 0.0f , 0.0f , 0.0f );
}

void DrawGround()
{
 GLint iLine;

 glColor4f( 0.5 , 0.5 , 0.5 , 0.6 );
 glPolygonMode( GL_FRONT_AND_BACK , GL_FILL );
 glBegin( GL_QUADS );
 glVertex3f( -F_EXTENT , Y_GROUND-0.05 , -F_EXTENT );
 glVertex3f( -F_EXTENT , Y_GROUND-0.05 , F_EXTENT );
 glVertex3f( F_EXTENT , Y_GROUND-0.05 , F_EXTENT );
 glVertex3f( F_EXTENT , Y_GROUND-0.05 , -F_EXTENT );
 glEnd();

 glColor4f( 1.0 , 1.0 , 1.0 , 0.6 );
 glPolygonMode( GL_FRONT_AND_BACK , GL_LINE );
 glBegin( GL_LINES );
 for( iLine = -F_EXTENT; iLine <= F_EXTENT; iLine += F_STEP )
 {
  glVertex3f( iLine , Y_GROUND , F_EXTENT );
  glVertex3f( iLine , Y_GROUND , -F_EXTENT );

  glVertex3f( F_EXTENT , Y_GROUND , iLine );
  glVertex3f( -F_EXTENT , Y_GROUND , iLine );
 }//for
 glEnd();
}

void Display()
{
 GLfloat x1 , y1 , x2 , y2 , z , r , angle;
 GLfloat xx1 , zz1 , xx2 , zz2;
 glEnable( GL_DEPTH_TEST );

 glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );

 //加入fog效果
 GLfloat fBackColor[] = { 0.0f , 0.0f , 0.0f , 0.0f };
 glEnable( GL_FOG );
 glFogfv( GL_FOG_COLOR , fBackColor );
 glFogf( GL_FOG_START , 5.0f );
 glFogf( GL_FOG_END , 70.0f );
 glFogi( GL_FOG_MODE , GL_LINEAR );

 glPushMatrix();
 glColor4f( 0.2 , 0.5 , 0.8 , 0.0 );
 for( angle = 0; angle <= 2*PI; angle += (PI/18) )
 {
  glPolygonMode( GL_FRONT , GL_FILL );
  glBegin( GL_TRIANGLE_STRIP );
  for( z = -R; z <= R; z += 0.5 )
  {
   r = sqrt( R*R - z*z );
   x1 = r*cos(angle);
   y1 = r*sin(angle)+7;
   x2 = r*cos(angle+(PI/18));
   y2 = r*sin(angle+(PI/18))+7;
   
   glVertex3f( x1 , -y1-7 , z );
   glVertex3f( x2 , -y2-7 , z );
  }//for
  glEnd();
 }//for

 glDisable( GL_LIGHTING );
 glEnable( GL_BLEND );
 glBlendFunc( GL_SRC_ALPHA , GL_ONE_MINUS_SRC_ALPHA );

  DrawGround();

 glDisable( GL_BLEND );
 glEnable( GL_LIGHTING );

 glPopMatrix();

 glPushMatrix();
  //glLoadIdentity();
  glLightfv( GL_LIGHT0 , GL_POSITION , lightPos );
  glLightfv( GL_LIGHT0 , GL_SPOT_DIRECTION , spotDir );

  glTranslatef( lightPos[0] , lightPos[1] , lightPos[2] );

  glPushAttrib( GL_LIGHTING_BIT );
   glDisable( GL_LIGHTING );
   glColor3ub( 255 , 255 , 0 );
   glPolygonMode( GL_FRONT , GL_FILL );
   glutSolidSphere( 3.0f , 15 , 15 );
  glPopAttrib();
 glPopMatrix();

 //glPolygonMode( GL_FRONT , GL_FILL );
 for( angle = 0; angle <= 2*PI; angle += (PI/18) )
 {
  glPolygonMode( GL_FRONT , GL_FILL );
  glColor3f( 0.2 , 0.5 , 0.8 );
  glBegin( GL_TRIANGLE_STRIP );
  for( z = -R; z <= R; z += 0.5 )
  {
   r = sqrt( R*R - z*z );
   x1 = r*cos(angle);
   y1 = r*sin(angle)+7;
   x2 = r*cos(angle+(PI/18));
   y2 = r*sin(angle+(PI/18))+7;
   
   glVertex3f( x1 , y1 , z );
   glVertex3f( x2 , y2 , z );
  }//for
  glEnd();

  //画影子
  glColor3f( 0.0 , 0.0 , 0.0 );
  glDisable( GL_LIGHTING );
  glBegin( GL_TRIANGLE_STRIP );
  for( z = -R; z <= R; z += 0.5 )
  {
   r = sqrt( R*R - z*z );
   x1 = r*cos(angle);
   y1 = r*sin(angle)+7;
   x2 = r*cos(angle+(PI/18));
   y2 = r*sin(angle+(PI/18))+7;

   xx1 = ( (x1-lightPos[0])/(y1-lightPos[1]) ) * ( Y_GROUND-lightPos[1] ) + x1;
   zz1 = ( (z-lightPos[0])/(y1-lightPos[1]) ) * ( Y_GROUND-lightPos[1] ) + z;

   xx2 = ( (x2-lightPos[0])/(y2-lightPos[1]) ) * ( Y_GROUND-lightPos[1] ) + x2;
   zz2 = ( (z-lightPos[0])/(y2-lightPos[1]) ) * ( Y_GROUND-lightPos[1] ) + z;
   
   glVertex3f( xx1 , Y_GROUND , zz1 );
   glVertex3f( xx2 , Y_GROUND , zz2 );
  }//for
  glEnd();
  glEnable( GL_LIGHTING );
 }//for

 /*glBegin( GL_POINTS );*/
 //GLfloat i , j , k;
 //for( i=0; i<255; i+=3 )
 // for( j=0; j<255; j+=3 )
 //  for( k=0; k<255; k+=3 )
 //  {
 //   glColor3ub( i , j , k );
 //   glVertex3f( i/50 , j/50 , k/50-10 );
 //  }//for
 /*glEnd();*/

 glutSwapBuffers();
}

void Resize( int w , int h )
{
 GLfloat fAspect;
 if( 0 == h )  h = 1;
 glViewport( 0 , 0 , w ,h );
 fAspect = (GLfloat)w / (GLfloat)h;

 glMatrixMode( GL_PROJECTION );
 glLoadIdentity();

 gluPerspective( 60.0f , fAspect , 1.0 , 400.0 );

 glMatrixMode( GL_MODELVIEW );
 glLoadIdentity();
 glTranslatef( 0 , 0 , -30 );

 ::glutPostRedisplay();
}

void Key( unsigned char k , int x , int y )
{
 GLfloat lastMatrix[ 16 ];
 glMatrixMode( GL_MODELVIEW );
 glGetFloatv( GL_MODELVIEW_MATRIX , lastMatrix );
 glLoadIdentity();
 switch( k )
 {
  case 'w':
   glTranslatef( 0.0f , 0.0f , keyStep );
   break;

  case 'a':
   glTranslatef( keyStep , 0.0f , 0.0f );
   break;

  case 's':
   glTranslatef( 0.0f , 0.0f , -keyStep );
   break;

  case 'd':
   glTranslatef( -keyStep , 0.0f , 0.0f );
   break;

  default:
   break;
 }//switch
 glMultMatrixf( lastMatrix );
 glutPostRedisplay();
}

void Motion( int x , int y )
{
 GLfloat lastMatrix[ 16 ];
 
 glMatrixMode(GL_MODELVIEW);
 glGetFloatv(GL_MODELVIEW_MATRIX,lastMatrix);
 glLoadIdentity();
 glRotatef( (GLfloat)(y-my)/10 , 1.0f , 0.0f , 0.0f );
 glRotatef( (GLfloat)(x-mx) , 0.0f , 1.0f , 0.0f );
 glMultMatrixf(lastMatrix);
 glutPostRedisplay();

 mx = x;
 my = y;
}

void Mouse( int button , int state , int x , int y )
{
 if( GLUT_LEFT_BUTTON == button )
 {
  if( GLUT_DOWN == state )
  {
   mx = x;
   my = y;
  }//if
 }//if
}

int main( int argc , char** argv )
{
 glutInit( &argc , argv );
 glutInitDisplayMode( GLUT_DOUBLE | GLUT_RGBA | GLUT_DEPTH | GLUT_MULTISAMPLE );
 glutInitWindowSize( 800 , 600 );
 glutInitWindowPosition( 200 , 100 );
 glutCreateWindow( "Tom" );

 init();

 glutDisplayFunc( Display );
 glutReshapeFunc( Resize );
 glutKeyboardFunc( Key );
 glutMotionFunc( Motion );
 glutMouseFunc( Mouse );
 //glutTimerFunc( 100 , MyTimer , 0 );

 glutMainLoop();

 return 0;
}