/**************************************************/
/* Random faults applied to a quadrilateral       */
/* f - switches between fill and line mode        */
/* r - turns on and off rotation                  */
/* space - one more step                          */
/* (C) Bedrich Benes 2003			              */
/* bbenes@purdue.ed     					      */
/**************************************************/

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

#define MAX 70
#define SCENE 1


GLint n=1;
GLfloat a[MAX][MAX];
GLint rotate;
GLint fill=1;


void Idle(void)
{
    if (rotate) glRotatef(1,1,1,1);
	glClear(GL_COLOR_BUFFER_BIT); //clear all
	glCallList(SCENE);
	glutSwapBuffers();
}

void Display(void)
{
    register i,j;
    
    glNewList(SCENE,GL_COMPILE);
    if (fill) glPolygonMode(GL_FRONT_AND_BACK,GL_FILL);
		else glPolygonMode(GL_FRONT_AND_BACK,GL_LINE);
	for (i=0;i<MAX-1;i++)
	{
		glBegin(GL_QUAD_STRIP);
		for (j=0;j<MAX;j++)
		{
			glColor3f(a[i][j],a[i][j],a[i][j]);
			glVertex3f(i/(GLfloat)MAX,j/(GLfloat)MAX,a[i][j]);
			glVertex3f((i+1)/(GLfloat)MAX,j/(GLfloat)MAX,a[i+1][j]);
		}
		glEnd();
	}
	glEndList();
}


void MyInit(void)
{
  register i,j;

  glClearColor(1.0, 1.0, 1.0, 1.0);
  for (i=0;i<MAX;i++)
  for (j=0;j<MAX;j++)
	  a[i][j]=0.5;

}


void myReshape(int w, int h)
{
  glViewport(0, 0, w, h);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  glOrtho(-0.2,1.2,-0.2,1.2,-10,10);
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
}


void GetLine(GLfloat *a, GLfloat *v)
{
  GLfloat b[3],size;
	
  a[0]=(GLfloat)1.f*rand()/RAND_MAX;
  a[1]=(GLfloat)1.f*rand()/RAND_MAX;;

  b[0]=(GLfloat)1.f*rand()/RAND_MAX;
  b[1]=(GLfloat)1.f*rand()/RAND_MAX;

  v[0]=b[0]-a[0];
  v[1]=b[1]-a[1];

  size=sqrt(v[0]*v[0]+v[1]*v[1]);
  v[0]/=size;
  v[1]/=size;
}

GLfloat Dot(GLfloat *a, GLfloat *b)
{
   return a[0]*b[0]+a[1]*b[1];
}

void RandomFault(void)
{   
	GLfloat x[2],v[2],pos[2],hlp[2],size,tmp,elev;
	register i,j;
   
	GetLine(x,v);
	elev=0.01;  //add 1% of the size
	for (i=0;i<MAX;i++)
	{
		for (j=0;j<MAX;j++)
		{
  		   pos[0]=(GLfloat)j/MAX;
		   pos[1]=(GLfloat)i/MAX;
		   hlp[0]=pos[0]-x[0];
		   hlp[1]=pos[1]-x[1];
		   size=sqrt(hlp[0]*hlp[0]+hlp[1]*hlp[1]);
		   hlp[0]/=size;
		   hlp[1]/=size;
           tmp=hlp[0];
		   hlp[0]=-hlp[1];
		   hlp[1]=tmp;
		   if (Dot(hlp,v)>0) a[i][j]+=elev;
					   else	 a[i][j]-=elev;
			
		}
	}
}


void Key(unsigned char key, GLint i, GLint j)
{
	switch(key){
    case 'r' : 
    case 'R' : rotate=(rotate==0);break;
    case 'f' : 
    case 'F' : fill=(fill==0);glutPostRedisplay();break;
    case ' ' : RandomFault();glutPostRedisplay();break;
    case 27 :
    case 'q':
	case 'Q': exit(0);
	}
}

int main(int argc, char **argv)
{
  srand(5);
  glutInitWindowSize(500,500);
  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA);
  glutCreateWindow("Random Faults");
  MyInit();
  glutDisplayFunc(Display);
  glutIdleFunc(Idle);
  glutKeyboardFunc(Key);
  glutReshapeFunc(myReshape);
  glutMainLoop();
  return 0;
}