/* plot3d.c                                          */
/* move x, X, y, Y, z, Z */

/* We use the plot3d view function in the display callback to point
   the object, whose position can be altered by the
   x,X,y,Y,z and Z keys for object position
   r,R,p,P,h and H keys for rool, pitch and heading
   s,S kets for scale
   The view is set in the reshape callback */
   
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <GL/glut.h>
#undef  abs
#define abs(a) ((a)<0.0?(-(a)):(a))
#undef  min
#define min(a,b) ((a)<(b)?(a):(b))
#undef  max
#define max(a,b) ((a)>(b)?(a):(b))

static GLfloat xoff=0.0;
static GLfloat yoff=0.0;
static GLfloat zoff=0.0;
static GLfloat roll   =15.0;
static GLfloat pitch  =30.0;
static GLfloat heading=45.0;
static GLfloat scale=0.0625;
static GLfloat xmin=0.0;
static GLfloat xmax=4.0;
static GLfloat ymin=0.0;
static GLfloat ymax=4.0;
static GLfloat zmin=0.0;
static GLfloat zmax=4.0;
static GLfloat zsmall;
static GLfloat zlarge;
static int n = 33;

/* define function F(x,y) to be plotted */
double F1(double x,double y)
{
  return 2.0*x+3.0*x*x+y+2.0*x*y-31.0;
}
double F2(double x,double y)
{
  return (-x)+x*x+2.0*y+x*y-14.0;
}
double F(double x,double y)
{
  return abs(F1(x,y))+abs(F2(x,y));
}

static void printstring(void *font, char msg[])
{
   int len, i;

   len = (int)strlen(msg);
   for(i=0; i<len; i++)
      glutBitmapCharacter(font, msg[i]);
} /* end printstring */

void display(void)
{
  char text[]="move object using x, X, y, Y, z, Z,  clear c, C";
  char text2[]="roll, pitch, heading  r, R, p, P, h, H,  scale Z s, S";
  char *p;
  int i, j;
  GLfloat x, y, z, dx, dy;

  zsmall = 1000.0;
  zlarge = -1000.0;
  
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  /* Update object position in modelview matrix */
  glPushMatrix();
    glLoadIdentity();
    glTranslatef(xoff, yoff, zoff);
    glRotatef(roll, 0.0, 0.0, 1.0);
    glRotatef(pitch, 0.0, 1.0, 0.0);
    glRotatef(heading, 1.0, 0.0, 0.0);
    glColor3f(0.1, 0.1, 0.1); /* dark gray */
    glScalef(1.0, 1.0, 1.0);
    /* draw object*/
    glBegin(GL_LINES);
      x = xmin;
      dx = (xmax-xmin)/(double)(n-1);
      dy = (ymax-ymin)/(double)(n-1);
      for(i=0; i<n-1; i++)
      {
        y = ymin;
        for(j=0; j<n-1; j++)
        {
          z = F(x,y)*scale;
          zsmall = min(zsmall,z);
          zlarge = max(zlarge,z);
          glVertex3f(x,y,z);
          glVertex3f(x+dx,y,F(x+dx,y)*scale);
          glVertex3f(x,y,z);
          glVertex3f(x,y+dy,F(x,y+dy)*scale);          
          y = y+dy;
        }
        x = x+dx;
      }
      x = xmax;
      y = ymin;
      for(j=0; j<n-1; j++)
      {
        z = F(x,y)*scale;
          zsmall = min(zsmall,z);
          zlarge = max(zlarge,z);
        glVertex3f(x,y,z);
        glVertex3f(x,y+dy,F(x,y+dy)*scale);          
        y = y+dy;
      }
      x = xmin;
      y = ymax;
      for(i=0; i<n-1; i++)
      {
        z = F(x,y)*scale;
        zsmall = min(zsmall,z);
        zlarge = max(zlarge,z);
        glVertex3f(x,y,z);
        glVertex3f(x+dx,y,F(x+dx,y)*scale);          
        x = x+dx;
      }
      
    glEnd();
    glColor3f(1.0, 0.0, 0.0);
    glBegin(GL_LINES);
      glVertex3f(-xmax, 0.0, 0.0);
      glVertex3f(xmax, 0.0, 0.0);
    glEnd();
    glPushMatrix(); /* apply text */
      glTranslatef(xmax, 0.0, 0.0);
      glScalef(0.003, 0.003, 1.0);
      glutStrokeCharacter(GLUT_STROKE_ROMAN, 'X');
    glPopMatrix();
    glColor3f(0.0, 1.0, 0.0);
    glBegin(GL_LINES);
      glVertex3f(0.0, -ymax, 0.0);
      glVertex3f(0.0, ymax, 0.0);
    glEnd();
    glPushMatrix(); /* apply text */
      glTranslatef(0.0, ymax, 0.0);
      glScalef(0.003, 0.003, 1.0);
      glutStrokeCharacter(GLUT_STROKE_ROMAN, 'Y');
    glPopMatrix();
    glColor3f(0.0, 0.0, 1.0);
    glBegin(GL_LINES);
      glVertex3f(0.0, 0.0, -zmax);
      glVertex3f(0.0, 0.0, zmax);
    glEnd();
    glPushMatrix(); /* apply text */
      glTranslatef(0.0, 0.0, zmax);
      glScalef(0.003, 0.003, 1.0);
      glutStrokeCharacter(GLUT_STROKE_ROMAN, 'Z');
    glPopMatrix();
    printf("zsmall=%g, zlarge=%g \n", zsmall, zlarge);
    printf("xoff=%g, yoff=%g, zoff=%g \n", xoff, yoff, zoff);
    printf("roll=%g, pitch=%g, heading=%g \n", roll, pitch, heading);
    printf("scale=%g \n", scale);
  glPopMatrix();
  
  glPushMatrix(); /* apply text */
    glLoadIdentity();
    glColor3f(1.0, 0.0, 0.0);
    glRasterPos2f(-xmax+0.1, -ymax+0.35);
    printstring(GLUT_BITMAP_TIMES_ROMAN_24, text);
    glRasterPos2f(-xmax+0.1, -ymax+0.1);
    printstring(GLUT_BITMAP_TIMES_ROMAN_24, text2);
  glPopMatrix();

  glFlush();
  glutSwapBuffers();
}

void keys(unsigned char key, int x, int y)
{
  /* Use x, X, y, Y, z, and Z keys to move object */
  if(key == 'x') xoff -= 0.5;
  if(key == 'X') xoff += 0.5;
  if(key == 'y') yoff -= 0.5;
  if(key == 'Y') yoff += 0.5;
  if(key == 'z') zoff -= 0.5;
  if(key == 'Z') zoff += 0.5;
  /* Use r, R, p, P, h, and H keys to move roll, pitch, heading */
  if(key == 'r') roll    -= 5.0;
  if(key == 'R') roll    += 5.0;
  if(key == 'p') pitch   -= 5.0;
  if(key == 'P') pitch   += 5.0;
  if(key == 'h') heading -= 5.0;
  if(key == 'H') heading += 5.0;
  if(key == 's') scale   /= 2.0;
  if(key == 'S') scale   *= 2.0;
  if(key == 'c' || key == 'C')
  { xoff=0.0; yoff=0.0; zoff=0.0; roll=0.0; pitch=-90.0; heading=0.0; scale=0.0625;}
  display();
}

void myReshape(int w, int h)
{
  glViewport(0, 0, w, h);
  /* Use a perspective view */
  glMatrixMode(GL_PROJECTION); 
  glLoadIdentity();
  glOrtho(-xmax, xmax, -ymax, ymax, -zmax, zmax);
  glMatrixMode(GL_MODELVIEW);
  glClearColor(1.0,1.0,1.0,0.0);
}

int main(int argc, char *argv[])
{
  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
  glutInitWindowSize(600, 600);
  glutCreateWindow(argv[0]);
  glutReshapeFunc(myReshape);
  glutDisplayFunc(display);
  glutKeyboardFunc(keys);
  glEnable(GL_DEPTH_TEST);
  glutMainLoop();
  return 0;
}