Merge pull request #92 from LDMX-Software/iss91

Factor out rotations to hcal geometry condition

Author: EinarElen

src/SimCore/SDs/HcalSD.cxx

@@ -44,7 +44,7 @@ ldmx::HcalID HcalSD::decodeCopyNumber(const std::uint32_t copyNumber,
 
     // 5cm wide bars are HARD-CODED
     if (section == ldmx::HcalID::BACK) {
-      if (geometry.layerIsHorizontal(layer)) {
+      if (geometry.backLayerIsHorizontal(layer)) {
         stripID = int((localPosition.y() + scint->GetYHalfLength()) / 50.0);
       } else {
         stripID = int((localPosition.x() + scint->GetXHalfLength()) / 50.0);
@@ -169,75 +169,34 @@ G4bool HcalSD::ProcessHits(G4Step* aStep, G4TouchableHistory* ROhist) {
   // Convert back to mm
   hit.setPathLength(stepLength * CLHEP::cm / CLHEP::mm);
   hit.setVelocity(track->GetVelocity());
-  // Convert pre/post step position from global coordinates to coordinates within the
-  // scintillator bar
-  const auto localPreStepPoint{topTransform.TransformPoint(prePoint->GetPosition())};
-  const auto localPostStepPoint{topTransform.TransformPoint(postPoint->GetPosition())};
-
-  /**
-   * topTransform translates to the local bar but does not do the rotation
-   * (this is because we don't do a rotation when placing the bars in the GDML)
-   *
-   * the logic below does the rotation to the local coordiates where 
-   *  x : short transverse side of bar
-   *  y : long transverse side of bar
-   *  z : along length of bar
-   *
-   * a lot of this logic could (and should) probably be moved into the geometry
-   * condition for the HCal so that it is more easily maintainable
-   *
-   * @note This logic only applies to the v14 and prototype detector; however,
-   * support for v12 is not broken because no studies using these pre/post step
-   * positions have been (or should be) done with the v12 detector.
-   */
-  const auto& geometry = getCondition<ldmx::HcalGeometry>(
+  const auto &geometry = getCondition<ldmx::HcalGeometry>(
       ldmx::HcalGeometry::CONDITIONS_OBJECT_NAME);
-  switch (id.getSection()) {
-    case ldmx::HcalID::BACK   : 
-      if (geometry.layerIsHorizontal(id.layer())) {
-        hit.setPreStepPosition(localPreStepPoint[2], localPreStepPoint[1], localPreStepPoint[0]);
-        hit.setPostStepPosition(localPostStepPoint[2], localPostStepPoint[1], localPostStepPoint[0]);
-      } else {
-        hit.setPreStepPosition(localPreStepPoint[2], localPreStepPoint[0], localPreStepPoint[1]);
-        hit.setPostStepPosition(localPostStepPoint[2], localPostStepPoint[0], localPostStepPoint[1]);
-      }
-      break;
-    case ldmx::HcalID::TOP    :
-    case ldmx::HcalID::BOTTOM : 
-      if (id.layer() % 2 == 0) {
-        hit.setPreStepPosition(localPreStepPoint[1], localPreStepPoint[2], localPreStepPoint[0]);
-        hit.setPostStepPosition(localPostStepPoint[1], localPostStepPoint[2], localPostStepPoint[0]);
-      } else {
-        hit.setPreStepPosition(localPreStepPoint[1], localPreStepPoint[0], localPreStepPoint[2]);
-        hit.setPostStepPosition(localPostStepPoint[1], localPostStepPoint[0], localPostStepPoint[2]);
-      }
-      break;
-    case ldmx::HcalID::RIGHT  : 
-    case ldmx::HcalID::LEFT   : 
-      if (id.layer() % 2 == 0) {
-        hit.setPreStepPosition(localPreStepPoint[0], localPreStepPoint[2], localPreStepPoint[1]);
-        hit.setPostStepPosition(localPostStepPoint[0], localPostStepPoint[2], localPostStepPoint[1]);
-      } else {
-        hit.setPreStepPosition(localPreStepPoint[0], localPreStepPoint[1], localPreStepPoint[2]);
-        hit.setPostStepPosition(localPostStepPoint[0], localPostStepPoint[1], localPostStepPoint[2]);
-      }
-      break;
-    default : 
-      EXCEPTION_RAISE("HcalSDHit","Found an unknown HCal section");
-  }
+  // Convert pre/post step position from global coordinates to coordinates
+  // within the scintillator bar
+  const auto localPreStepPoint{
+      topTransform.TransformPoint(prePoint->GetPosition())};
+  const auto localPostStepPoint{
+      topTransform.TransformPoint(postPoint->GetPosition())};
+
+  // And rotate them to a local coordinate system for the bar that always has
+  // the same x/y/z definitions (see HcalGeometry for details)
+  auto localPrePositionRotated{geometry.rotateGlobalToLocalBarPosition(
+      {localPreStepPoint[0], localPreStepPoint[1], localPreStepPoint[2]}, id)};
+
+  auto localPostPositionRotated{geometry.rotateGlobalToLocalBarPosition(
+      {localPostStepPoint[0], localPostStepPoint[1], localPostStepPoint[2]},
+      id)};
+  hit.setPreStepPosition(localPrePositionRotated[0], localPrePositionRotated[1],
+                         localPrePositionRotated[2]);
+  hit.setPostStepPosition(localPostPositionRotated[0],
+                          localPostPositionRotated[1],
+                          localPostPositionRotated[2]);
   hit.setPreStepTime(prePoint->GetGlobalTime());
   hit.setPostStepTime(postPoint->GetGlobalTime());
 
-  // do we want to set the hit coordinate in the middle of the absorber?
-  // G4ThreeVector volumePosition =
-  // aStep->GetPreStepPoint()->GetTouchableHandle()->GetHistory()->GetTopTransform().Inverse().TransformPoint(G4ThreeVector());
-  // if (section==ldmx::HcalID::BACK) hit->setPosition(position[0], position[1],
-  // volumePosition.z()); elseif (section==ldmx::HcalID::TOP ||
-  // section==ldmx::HcalID::BOTTOM) hit->setPosition(position[0], volumePosition.y(),
-  // position[2]); elseif (section==ldmx::HcalID::LEFT || section==ldmx::HcalID::RIGHT)
-  // hit->setPosition(volumePosition.x(),position[1] , position[2]);
-
-  if (this->verboseLevel > 2) { hit.Print(); }
+  if (this->verboseLevel > 2) {
+    hit.Print();
+  }
 
   return true;
 }