/********************************/
/* Lighting example             */
/* (C) Bedrich Benes 2000		*/ 
/********************************/

#include <GL/glut.h>
#include <stdio.h>
#include <stdlib.h>
#include <math.h>

#define MAX 10
#define AMPLITUDE 0.05
#define FREQUENCY 15


void Reshape(int w, int h)
{
  glViewport(0, 0, w, h);       
  glMatrixMode(GL_PROJECTION);  
  glLoadIdentity();             
  glOrtho(-1, 1, -1, 1, -100, 100);//working area is ...
}

void Init()
{

  GLfloat spec[]={1,1,1};
  GLfloat diff[] ={1,1,0};
  GLfloat pos[] ={1,1,1};


  glEnable(GL_AUTO_NORMAL) ;
  glClearColor(0.1,0.1,0.1,1);
  glShadeModel(GL_SMOOTH);
  glEnable(GL_LIGHTING);
  glEnable(GL_LIGHT0);
  glLightfv(GL_LIGHT0, GL_DIFFUSE, diff);
  glLightfv(GL_LIGHT0, GL_SPECULAR, spec);
  glLightfv(GL_LIGHT0, GL_POSITION, pos);

  glMatrixMode(GL_PROJECTION);  
  glLoadIdentity();             
  glOrtho(-1, 1, -1, 1, -100, 100);//working area is ...
  printf("q to quit\n");
}


GLfloat f(GLfloat x, GLfloat z, GLfloat t)
{

  return(AMPLITUDE*sin(x*FREQUENCY+t)-0.5);
  return(0);

}

void Normf(GLfloat x, GLfloat z, GLfloat t,
		   GLfloat *nx, GLfloat *ny, GLfloat *nz)
{
  GLfloat size;

  	
  *nx = -AMPLITUDE*FREQUENCY*cos(x*FREQUENCY+t);
  *ny = 1;
  *nz = 0;

  size = (*nx * *nx+ *ny * *ny + *nz * *nz);
  size=sqrt(size);
  *nx /= size;
  *ny /= size;
  *nz /= size;
}


void DisplayWave()
{
  int i,j;
  GLfloat x,y,z;
  GLfloat nx,ny,nz;
  static GLfloat t;

  t += 0.1;
  glBegin(GL_TRIANGLES);
  for (i=0;i<MAX;i++)
  for (j=0;j<MAX;j++)
  {
	x = (GLfloat) i/MAX-0.5;
	z = (GLfloat) j/MAX-0.5;
	y = f(x,z,t);
	Normf(x,z, t, &nx, &ny, &nz);
	glNormal3f(nx,ny,nz);
	glVertex3f(x,y,z);

	x = (GLfloat) (i+1)/MAX-0.5;
	z = (GLfloat) j/MAX-0.5;
	y = f(x,z,t);
	Normf(x,z, t, &nx, &ny, &nz);
	glNormal3f(nx,ny,nz);
	glVertex3f(x,y,z);

	x = (GLfloat) (i+1)/MAX-0.5;
	z = (GLfloat) (j+1)/MAX-0.5;
	y = f(x,z,t);
	Normf(x,z, t, &nx, &ny, &nz);
	glNormal3f(nx,ny,nz);
	glVertex3f(x,y,z);

	x = (GLfloat) i/MAX-0.5;
	z = (GLfloat) j/MAX-0.5;
	y = f(x,z,t);
	Normf(x,z, t, &nx, &ny, &nz);
	glNormal3f(nx,ny,nz);
	glVertex3f(x,y,z);

	x = (GLfloat) i/MAX-0.5;
	z = (GLfloat) (j+1)/MAX-0.5;
	y = f(x,z,t);
	Normf(x,z, t, &nx, &ny, &nz);
	glNormal3f(nx,ny,nz);
	glVertex3f(x,y,z);

	x = (GLfloat) (i+1)/MAX-0.5;
	z = (GLfloat) (j+1)/MAX-0.5;
	y = f(x,z,t);
	Normf(x,z, t, &nx, &ny, &nz);
	glNormal3f(nx,ny,nz);
	glVertex3f(x,y,z);

  
  }
  glEnd();


}

void DisplayScene(void)
{
  static GLfloat i;
  GLfloat matdiff[]={.8, .8 , .8};
  GLfloat matspec[]={.2, 0 , 0};

  glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE, matdiff);
  glMaterialfv(GL_FRONT_AND_BACK, GL_SPECULAR, matspec);
  glClear(GL_COLOR_BUFFER_BIT);
  glRotatef(i+=0.1,0,1,0); 
  if (i>360) i=0;
  DisplayWave();
  glutSwapBuffers();
}


void Idle(void)
{

  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
  glRotatef(45,1,1,1);
  DisplayScene();
}

void Display(void)
{

}

//keyboard hit causes the program to exit
void Kbd(unsigned char a, int x, int y)
{
	switch(a)
	{
	 case 'q': exit(0);break;
	}
	Display();
}

int main(int argc, char **argv)
{
  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA);
  glutCreateWindow("Sinusoidal wave");
  glutDisplayFunc(Display);
  glutIdleFunc(Idle);
  glutReshapeFunc(Reshape);
  glutKeyboardFunc(Kbd);
  Init();
  glutMainLoop();
  return 0;        
}