Merge pull request #1590 from CesiumGS/sun-sky-time-zone

Add `UpdateTimeZoneFromLongitude` to `ACesiumSunSky`

CHANGES.md

@@ -5,6 +5,8 @@
 ##### Additions :tada:
 
 - Added `CesiumUrlTemplateRasterOverlay`, allowing a raster overlay to be added using tiles requested based on a specified URL template.
+- Added `EstimateTimeZoneForLongitude` method to `ACesiumSunSky` to set a reasonable `TimeZone` value at the given longitude.
+- The "Place Georeference Origin Here" button on `ACesiumGeoreference` will now adjust the time zone of the `ACesiumSunSky` instances that reference it, based on the new origin's longitude. This improves user experience when moving the origin to locations where it would be nighttime in the current time zone.
 - Added `RequestHeaders` property to `Cesium3DTileset`, allowing per-tileset headers to be specified.
 - Added `RequestHeaders` properties to `CesiumTileMapServiceRasterOverlay`, `CesiumUrlTemplateRasterOverlay`, `CesiumWebMapServiceRasterOverlay`,
   and `CesiumWebMapTileServiceRasterOverlay`, allowing per-raster-overlay HTTP headers to be specified.

Source/CesiumRuntime/Private/CesiumGeoreference.cpp

@@ -7,10 +7,12 @@
 #include "CesiumCommon.h"
 #include "CesiumCustomVersion.h"
 #include "CesiumGeospatial/Cartographic.h"
+#include "CesiumGlobeAnchorComponent.h"
 #include "CesiumOriginShiftComponent.h"
 #include "CesiumRuntime.h"
 #include "CesiumSubLevelComponent.h"
 #include "CesiumSubLevelSwitcherComponent.h"
+#include "CesiumSunSky.h"
 #include "CesiumTransforms.h"
 #include "CesiumUtility/Math.h"
 #include "Engine/LevelStreaming.h"
@@ -426,6 +428,24 @@ void ACesiumGeoreference::PlaceGeoreferenceOriginHere() {
           .Rotator());
   pEditorViewportClient->SetViewLocation(
       this->GetActorTransform().TransformPosition(FVector::ZeroVector));
+
+  const double NewLongitude = this->GetOriginLongitude();
+
+  // The georeference origin may have moved to a location across the world
+  // where it is nighttime in the currently set time zone. To improve user
+  // experience, we update the timezones of all the CesiumSunSky instances using
+  // this georeference so that the view is not completely dark.
+  for (TActorIterator<ACesiumSunSky> It(pWorld); It; ++It) {
+    if (!IsValid(It->GlobeAnchor)) {
+      continue;
+    }
+
+    ACesiumGeoreference* ResolvedGeoreference =
+        It->GlobeAnchor->GetResolvedGeoreference();
+    if (IsValid(ResolvedGeoreference) && ResolvedGeoreference == this) {
+      It->EstimateTimeZoneForLongitude(NewLongitude);
+    }
+  }
 }
 
 void ACesiumGeoreference::CreateSubLevelHere() {

Source/CesiumRuntime/Private/CesiumSunSky.cpp

@@ -567,6 +567,11 @@ void ACesiumSunSky::UpdateAtmosphereRadius() {
   }
 }
 
+void ACesiumSunSky::EstimateTimeZoneForLongitude(double InLongitude) {
+  this->TimeZone = FMath::Clamp(InLongitude, -180.0, 180.0) / 15.0;
+  this->UpdateSun();
+}
+
 void ACesiumSunSky::GetHMSFromSolarTime(
     double InSolarTime,
     int32& Hour,

Source/CesiumRuntime/Public/CesiumSunSky.h

@@ -444,6 +444,22 @@ class CESIUMRUNTIME_API ACesiumSunSky : public AActor {
   UFUNCTION(CallInEditor, BlueprintCallable, Category = "Cesium")
   void UpdateAtmosphereRadius();
 
+  /**
+   * Adjusts the time zone of this CesiumSunSky to an estimate based on the
+   * given longitude.
+   *
+   * The time zone is naively calculated from the longitude, where every
+   * 15 degrees equals 1 hour. This may not necessarily match the official
+   * time zone at a given location within that longitude.
+   *
+   * This method will call @ref UpdateSun automatically.
+   *
+   * @param InLongitude The longitude that the calculated time zone will be
+   * based on in degrees in the range [-180, 180].
+   */
+  UFUNCTION(CallInEditor, BlueprintCallable, Category = "Cesium")
+  void EstimateTimeZoneForLongitude(double InLongitude);
+
   /**
    * Convert solar time to Hours:Minutes:Seconds. Copied the implementation
    * from the engine SunSkyBP class.