Re: [ff3d-users] how define boundary condition ?

[DELPINO Stephane]

Dear Oka.

You can impose your Dirichlet condition using penalty:


double P=1E3; // example of penalty coefficient
function g = sin(x); // example of Dirichlet RHS

solve (u) in M
{
 test(v)
  int(grad(u)*grad(v)
+int(P*u*v*one(M1)) // penalty in mesh M1
 =
int(P*g*v*one(M1));  // penalty in mesh M2
}

This might be costly since 'one(M1)' need to check if any quadrature 
vertex of M is inside M1. Localizing in a 3D mesh can be expensive ...
You may prefer to use POV description
Then you replace 'one(M1)' by 'one(<1,0,0>)' if your object in the POV 
file has color <1,0,0>
You can also define an analytic function:
  function sphere=one((x-x0)^2+(y-y0)^2+(z-z0)^2<r0^2);

Best regards,
Stephane.