add Normals to meshes

src/HEP/Geant/EmitterPrimary.cpp

@@ -47,4 +47,103 @@ void EmitterPrimary::GeneratePrimaries(G4Event *anEvent) {
   // dell'energia.
 
   fParticleGun->GeneratePrimaryVertex(anEvent);
+}
+
+// -------------------------------------------------------------------------- //
+
+QuadMeshEmitterPrimary::QuadMeshEmitterPrimary()
+    : EmitterPrimary(), m_Mesh(nullptr), m_TotalArea(0.0) {
+}
+
+QuadMeshEmitterPrimary::~QuadMeshEmitterPrimary() {
+}
+
+void QuadMeshEmitterPrimary::SetMesh(uLib::QuadMesh *mesh) {
+  m_Mesh = mesh;
+  CalculateAreas();
+}
+
+void QuadMeshEmitterPrimary::CalculateAreas() {
+  if (!m_Mesh) return;
+  m_CumulativeAreas.clear();
+  m_TotalArea = 0.0;
+
+  const auto &points = m_Mesh->Points();
+  const auto &quads = m_Mesh->Quads();
+
+  for (const auto &q : quads) {
+    uLib::Vector3f v0 = points[q(0)];
+    uLib::Vector3f v1 = points[q(1)];
+    uLib::Vector3f v2 = points[q(2)];
+    uLib::Vector3f v3 = points[q(3)];
+
+    double a1 = 0.5 * (v1 - v0).cross(v2 - v0).norm();
+    double a2 = 0.5 * (v2 - v0).cross(v3 - v0).norm();
+    m_TotalArea += (a1 + a2);
+    m_CumulativeAreas.push_back(m_TotalArea);
+  }
+}
+
+void QuadMeshEmitterPrimary::GeneratePrimaries(G4Event *anEvent) {
+  if (!m_Mesh || m_TotalArea <= 0.0) return;
+
+  // 1. Choose a quad
+  double r = G4UniformRand() * m_TotalArea;
+  auto it = std::lower_bound(m_CumulativeAreas.begin(), m_CumulativeAreas.end(), r);
+  int quadIdx = std::distance(m_CumulativeAreas.begin(), it);
+
+  const auto &q = m_Mesh->Quads()[quadIdx];
+  const auto &points = m_Mesh->Points();
+  uLib::Vector3f v0 = points[q(0)];
+  uLib::Vector3f v1 = points[q(1)];
+  uLib::Vector3f v2 = points[q(2)];
+  uLib::Vector3f v3 = points[q(3)];
+
+  // 2. Choose a point on the quad
+  double a1 = 0.5 * (v1 - v0).cross(v2 - v0).norm();
+  double a2 = 0.5 * (v2 - v0).cross(v3 - v0).norm();
+  
+  G4ThreeVector pos;
+  uLib::Vector3f normal = m_Mesh->GetNormal(quadIdx);
+  
+  if (G4UniformRand() < a1 / (a1 + a2)) {
+    double u = G4UniformRand();
+    double v = G4UniformRand();
+    if (u + v > 1.0) { u = 1.0 - u; v = 1.0 - v; }
+    uLib::Vector3f p = v0 + u * (v1 - v0) + v * (v2 - v0);
+    pos.set(p(0), p(1), p(2));
+  } else {
+    double u = G4UniformRand();
+    double v = G4UniformRand();
+    if (u + v > 1.0) { u = 1.0 - u; v = 1.0 - v; }
+    uLib::Vector3f p = v0 + u * (v2 - v0) + v * (v3 - v0);
+    pos.set(p(0), p(1), p(2));
+  }
+
+  // 3. Choose a direction (Cosmic Muon: cos^2(theta))
+  G4ThreeVector dir;
+  bool accepted = false;
+  int tries = 0;
+  
+  while (!accepted && tries < 1000) {
+    tries++;
+    double cosTheta = std::pow(G4UniformRand(), 1.0/3.0);
+    double sinTheta = std::sqrt(1.0 - cosTheta * cosTheta);
+    double phi = 2.0 * M_PI * G4UniformRand();
+    
+    // Incoming from above (+Z towards -Z)
+    dir.set(sinTheta * std::cos(phi), sinTheta * std::sin(phi), -cosTheta);
+    
+    // Filtering: pointing on the same side of the face normal
+    if (dir.x() * normal(0) + dir.y() * normal(1) + dir.z() * normal(2) > 0) {
+      accepted = true;
+    }
+  }
+
+  if (accepted) {
+    fParticleGun->SetParticlePosition(pos);
+    fParticleGun->SetParticleMomentumDirection(dir);
+    // Keep energy from base class or set here if needed
+    fParticleGun->GeneratePrimaryVertex(anEvent);
+  }
 }