Fixed Traffic Signals being spawned in the air (#9239)

* Add AdjustSignHeightToGround method to ensure traffic signs are placed at the correct height

* use variable instead a magic number for the offset, and lowered it to 0.5 cm

Author: LuisPovedaCano

Unreal/CarlaUE4/Plugins/Carla/Source/Carla/Traffic/TrafficLightManager.cpp

@@ -572,6 +572,8 @@ void ATrafficLightManager::SpawnTrafficLights()
     SpawnRotation.Roll = 0;
     SpawnRotation.Pitch = 0;
 
+    AdjustSignHeightToGround(SpawnLocation);
+
     FActorSpawnParameters SpawnParams;
     SpawnParams.Owner = this;
     SpawnParams.SpawnCollisionHandlingOverride =
@@ -667,6 +669,8 @@ void ATrafficLightManager::SpawnSignals()
       SpawnRotation.Roll = 0;
       SpawnRotation.Pitch = 0;
 
+      AdjustSignHeightToGround(SpawnLocation);
+
       FActorSpawnParameters SpawnParams;
       SpawnParams.Owner = this;
       SpawnParams.SpawnCollisionHandlingOverride =
@@ -724,6 +728,8 @@ void ATrafficLightManager::SpawnSignals()
       SpawnRotation.Roll = 0;
       SpawnRotation.Pitch = 0;
 
+      AdjustSignHeightToGround(SpawnLocation);
+
       FActorSpawnParameters SpawnParams;
       SpawnParams.Owner = this;
       SpawnParams.SpawnCollisionHandlingOverride =
@@ -863,3 +869,30 @@ void ATrafficLightManager::RemoveAttachedProps(TArray<AActor*> Actors) const
     Actor->Destroy();
   }
 }
+
+void ATrafficLightManager::AdjustSignHeightToGround(FVector& SpawnLocation) const
+{
+  const FVector Start = SpawnLocation + FVector(0, 0, 10000.0f);
+  const FVector End = SpawnLocation - FVector(0, 0, 10000.0f);
+
+  FHitResult HitResult;
+  FCollisionQueryParams CollisionParams;
+  CollisionParams.bTraceComplex = true;
+  CollisionParams.bReturnPhysicalMaterial = false;
+
+  constexpr float ZOffsetSignToGround = 0.5f;
+  if (GetWorld()->LineTraceSingleByChannel(
+      HitResult,
+      Start,
+      End,
+      ECC_WorldStatic,
+      CollisionParams))
+  {
+    SpawnLocation.Z = HitResult.Location.Z + ZOffsetSignToGround;
+  }
+  else
+  {
+    carla::log_warning("Could not find ground for traffic sign placement at location",
+        TCHAR_TO_UTF8(*SpawnLocation.ToString()));
+  }
+}

Unreal/CarlaUE4/Plugins/Carla/Source/Carla/Traffic/TrafficLightManager.h

@@ -69,6 +69,8 @@ class CARLA_API ATrafficLightManager : public AActor
 
   void RemoveAttachedProps(TArray<AActor*> Actors) const;
 
+  void AdjustSignHeightToGround(FVector& SpawnLocation) const;
+
   // Mapped references to ATrafficLightGroup (junction)
   UPROPERTY()
   TMap<int, ATrafficLightGroup *> TrafficGroups;