process mesocrystal basis directly, w/o passing through slicing

Resample/Processed/Slicer.cpp

@@ -256,7 +256,23 @@ IReParticle* processBasis(const IParticle* basis, const Material& ambientMat)
         throw std::runtime_error("Mesocrystal with CoreAndShell basis not yet supported");
     }
     // Remaining case: the basis is a single particle.
-    return Compute::Slicing::particlesInSlice(basis, {}, ambientMat).release_back();
+    const auto* p = dynamic_cast<const Particle*>(basis);
+    ASSERT(p);
+    const IRotation* rot = p->rotation();
+    auto particleSlice = std::make_unique<ReParticle>(
+        *p->pFormfactor(), new const R3(p->particlePosition()),
+        rot && !rot->isIdentity() ? std::move(new const RotMatrix(rot->rotMatrix())) : nullptr);
+    if (!particleSlice)
+        return {};
+    double volume = particleSlice->volume();
+    Material transformed_material(p->rotation()
+                                      ? p->material()->rotatedMaterial(p->rotation()->rotMatrix())
+                                      : *p->material());
+    particleSlice->setMaterial(transformed_material);
+    particleSlice->setAdmixedFraction(volume);
+    particleSlice->setAdmixedMaterial(transformed_material);
+    particleSlice->setAmbientMaterial(ambientMat);
+    return particleSlice.release();
 }
 
 } // namespace