initialize ff directly

Resample/Processed/ProcessedLayout.cpp

@@ -106,25 +106,24 @@ CoherentFFSum ProcessedLayout::processParticle(const IParticle& particle, const
     std::vector<CoherentFFTerm> terms;
     for (size_t i = 0; i < sliced_ffs.size(); ++i) { // TODO provide slices_ffs.cbegin() etc
         const auto pair = sliced_ffs.getPair(i);
-        const IFormFactor& ff = *pair.first;
         const size_t iLayer = pair.second;
+        const Material& material = slices[iLayer].material();
+        const std::unique_ptr<IFormFactor> ff(pair.first->clone());
+        ff->setAmbientMaterial(material);
+
         std::unique_ptr<IComputeFF> computer;
         if (slices.size() > 1) {
             if (m_polarized)
-                computer = std::make_unique<ComputeDWBAPol>(ff, iLayer);
+                computer = std::make_unique<ComputeDWBAPol>(*ff, iLayer);
             else
-                computer = std::make_unique<ComputeDWBA>(ff, iLayer);
+                computer = std::make_unique<ComputeDWBA>(*ff, iLayer);
         } else {
             // no need for DWBA, use BA
             if (m_polarized)
-                computer = std::make_unique<ComputeBAPol>(ff, iLayer);
+                computer = std::make_unique<ComputeBAPol>(*ff, iLayer);
             else
-                computer = std::make_unique<ComputeBA>(ff, iLayer);
+                computer = std::make_unique<ComputeBA>(*ff, iLayer);
         }
-
-        const Material& slice_material = slices[iLayer].material();
-        computer->setAmbientMaterial(slice_material);
-
         terms.emplace_back(CoherentFFTerm(computer.release()));
     }
     return CoherentFFSum(abundance / total_abundance, terms);