AdvViz: add GetVertexPositionScaleFactor to UCesiumLoadedTile to make sense of glTF vertices

Author: GhisBntly

Source/CesiumRuntime/Private/CesiumGltfComponent.cpp

@@ -1558,6 +1558,8 @@ static void loadPrimitive(
   positionBuffer.Init(numVertices, false);
 
   {
+    // Note: scaling from glTF vertices to Unreal's must match
+    // UCesiumGltfComponent::GetGltfToUnrealLocalVertexPositionScaleFactor
     if (duplicateVertices) {
       TRACE_CPUPROFILER_EVENT_SCOPE(Cesium::CopyDuplicatedPositions)
       for (uint32 i = 0; i < numVertices; ++i) {
@@ -3601,6 +3603,15 @@ const Cesium3DTilesSelection::TileID& UCesiumGltfComponent::GetTileID() const {
   return pTile->getTileID();
 }
 
+FVector
+UCesiumGltfComponent::GetGltfToUnrealLocalVertexPositionScaleFactor() const {
+  // Note: replicates logic from (static) loadPrimitive
+  return FVector(
+      CesiumPrimitiveData::positionScaleFactor,
+      -CesiumPrimitiveData::positionScaleFactor,
+      CesiumPrimitiveData::positionScaleFactor);
+}
+
 void UCesiumGltfComponent::SetRenderReady(bool bToggle) {
   if (pTile) {
     pTile->setRenderEngineReadiness(bToggle);

Source/CesiumRuntime/Private/CesiumGltfComponent.h

@@ -140,6 +140,7 @@ class UCesiumGltfComponent : public USceneComponent, public ICesiumLoadedTile {
   // from ICesiumLoadedTile
   const FCesiumModelMetadata& GetModelMetadata() const override;
   const Cesium3DTilesSelection::TileID& GetTileID() const override;
+  FVector GetGltfToUnrealLocalVertexPositionScaleFactor() const override;
   void SetRenderReady(bool bToggle) override;
 
   void UpdateFade(float fadePercentage, bool fadingIn);

Source/CesiumRuntime/Public/CesiumLoadedTile.h

@@ -7,6 +7,7 @@
 #include "CesiumPrimitiveFeatures.h"
 #include "CesiumPrimitiveMetadata.h"
 
+#include "Math/Vector.h"
 #include "UObject/ObjectMacros.h"
 
 #include "CesiumLoadedTile.generated.h"
@@ -23,6 +24,11 @@ class ICesiumLoadedTile {
   /** Get the tile identifier: this is informational only, as there is no
    * guarantee of unicity */
   virtual const Cesium3DTilesSelection::TileID& GetTileID() const = 0;
+  /** Scaling factor to be applied (component-wise multiplication) to glTF
+   * vertices of this tile's models to obtain the values represented in their
+   * matching mesh component (see @{link
+   * UCesiumLoadedTilePrimitive::GetMeshComponent). */
+  virtual FVector GetGltfToUnrealLocalVertexPositionScaleFactor() const = 0;
   virtual const FCesiumModelMetadata& GetModelMetadata() const = 0;
   virtual void SetRenderReady(bool bToggle) = 0;
 };