message: Balance heuristic
diff: @@ -52,6 +52,18 @@ inline F radical_inverse(I n)
  } // detail
  +//-------------------------------------------------------------------------------------------------
  +// Calculate Veach's balance heuristic
  +//
  +
  +template <typename T>
  +VSNRAY_FUNC
  +T balance_heuristic(T const& pdf1, T const& pdf2)
  +{
  + return pdf1 / (pdf1 + pdf2);
  +}
  +
  +
  //-------------------------------------------------------------------------------------------------
  // Calculate Veach's power heuristic for p^2
  //
  