1. Why don't you write a decent documentation ?

       Because I don't like this tedious job.
       Besides, thousands (OK hundreds now) of users have
       used xd3d without a doc. It is built to be easy to use.

2. Can xd3d do cross-sections ?

       No. But if you are clever, you can do some cross-sections:
       Suppose you want to plot a scalar field "u" on the cross-section
       x=1 of your domain.
       a/ read a file containing the x value
       b/ plot the isosurface x=1
       c/ read the file containing the field u.
       d/ answer "1" to the question
  >>> Scalar field for a new isosurface (0) 
      or to draw a contour plot on the old one (1) ?

       Of course an easier procedure will be available in future releases.

3. Why Fortran ???
       
       Why not ?
       If it is a so big problem for you, you can convert the
       sources through "f2c" or rewrite the whole thing in 
       C++/Java/Ocaml :)

4. Any OpenGL version ?

       Not yet. The genesis of xd3d is very old, a time when
       OpenGL was not even dreamed. It has been written in a
       portable way with only basic graphical instructions.
       But I agree that an OpenGL version could be nice.