[vtkusers] invert the color of pixels

[Stephane Del Pino]

Hello Shang.

Sorry, the documentation is really out of date about standard FEM ...
Here is a simple example:

-----------------------------------
// read the mesh (not the .geo but the .msh)
mesh M = read(gmsh,"cube.msh");

//solve the problem
solve(u) in M
{
  pde(u)
   -div(grad(u)) = 1;
  u = 0 on 0; // applies Dirichlet on triangles of reference 0
}
-----------------------------------

I hope that helps,
Stéphane.