3.6 2D samples

This section is devoted to visualization of 2D data arrays. 2D means the data which depend on 2 indexes (parameters) like matrix z(i,j)=z(x(i),y(j)), i=1...n, j=1...m or in parametric form {x(i,j),y(i,j),z(i,j)}. Most of samples will use the same data for plotting. So, I put its initialization in separate function

void mgls_prepare2d(mglData *a, mglData *b=0, mglData *v=0)
{
  register long i,j,n=50,m=40,i0;
  if(a) a->Create(n,m);   if(b) b->Create(n,m);
  if(v) { v->Create(9); v->Fill(-1,1);  }
  mreal x,y;
  for(i=0;i<n;i++)  for(j=0;j<m;j++)
  {
    x = i/(n-1.); y = j/(m-1.); i0 = i+n*j;
    if(a) a->a[i0] = 0.6*sin(2*M_PI*x)*sin(3*M_PI*y)+0.4*cos(3*M_PI*x*y);
    if(b) b->a[i0] = 0.6*cos(2*M_PI*x)*cos(3*M_PI*y)+0.4*cos(3*M_PI*x*y);
  }
}

or using C functions

void mgls_prepare2d(HMDT a, HMDT b=0, HMDT v=0)
{
  register long i,j,n=50,m=40,i0;
  if(a) mgl_data_create(a,n,m,1);
  if(b) mgl_data_create(b,n,m,1);
  if(v) { mgl_data_create(v,9,1,1); mgl_data_fill(v,-1,1,'x');  }
  mreal x,y;
  for(i=0;i<n;i++)  for(j=0;j<m;j++)
  {
    x = i/(n-1.); y = j/(m-1.); i0 = i+n*j;
    if(a) mgl_data_set_value(a, 0.6*sin(2*M_PI*x)*sin(3*M_PI*y)+0.4*cos(3*M_PI*x*y), i,j,0);
    if(b) mgl_data_set_value(b, 0.6*cos(2*M_PI*x)*cos(3*M_PI*y)+0.4*cos(3*M_PI*x*y), i,j,0);
  }
}