electromagnetism - Calculating the resistance of a 3D shape between two points

If I have an arbitrarily shaped object made of a uniform material of some specified resistivity, how would I go about calculating the resistance between two measurement points with known contact geometry?

Is there a general formula for this? (other than just Maxwell's equations) If so, where would I find a derivation?

Edit: Some simulations re answer below:

Answer

Well, yes you can, but it is usually very hard. Here are the steps:

1. 
   

   Solve the Laplace equation: $$ \nabla^2V = 0 \, .$$ In your case, find the general solution in spherical coordinates. Try to use every simplification you can. You might wonder why you don't solve Poisson's equation:
   $$ \epsilon\nabla^2V = \rho \, .$$ That's because a conductor is an equal number of lattice positive and moving negative, so you have a net null density of charge.

   
   



2. 
   

   Find the electric field with:
   $$ E = -\nabla V $$ You should still have a term dependent on your $V_0$, the potential difference between your two points.

   
   


3. 
   

   Find the current density with: $$ J = \sigma E \, .$$

   
   


4. 
   

   Find the total current $I$ by integrating over any closed surface containing only one of your two contact point.

   
   



5. 
   

   $$V_0 = R I \, !$$

   
   

That's it. I have used it to find the resistance for certain geometries when you could do lots of simplifications to find the solution of $V$, but I don't know how it can be applied for more general problems.