Merge pull request #5351 from aws-lumberyard-dev/terrain/mbalfour/use_ground_plane_non_functional

Use Ground Plane non functional
Added functionality to the "Use Ground Plane" toggle. Now, when it's enabled, the Terrain Layer Spawner will always provide valid terrain data at the minimum height of the spawner box, even if no Terrain Height Gradient List exists. If it's disabled, it won't provide any terrain data unless the Terrain Height Gradient List exists.

Gems/Terrain/Code/Source/Components/TerrainHeightGradientListComponent.cpp

@@ -164,14 +164,17 @@ namespace Terrain
             // could just make this list a prioritized list from top to bottom for any points that overlap.
             for (auto& gradientId : m_configuration.m_gradientEntities)
             {
-                // If gradients ever provide bounds, or if we add a value threshold in this component, it would be possible for terrain
-                // to *not* exist at a specific point.
-                terrainExists = true;
+                if (gradientId.IsValid())
+                {
+                    // If gradients ever provide bounds, or if we add a value threshold in this component, it would be possible for terrain
+                    // to *not* exist at a specific point.
+                    terrainExists = true;
 
-                float sample = 0.0f;
-                GradientSignal::GradientRequestBus::EventResult(
-                    sample, gradientId, &GradientSignal::GradientRequestBus::Events::GetValue, params);
-                maxSample = AZ::GetMax(maxSample, sample);
+                    float sample = 0.0f;
+                    GradientSignal::GradientRequestBus::EventResult(
+                        sample, gradientId, &GradientSignal::GradientRequestBus::Events::GetValue, params);
+                    maxSample = AZ::GetMax(maxSample, sample);
+                }
             }
             m_isRequestInProgress = false;
         }

Gems/Terrain/Code/Source/TerrainSystem/TerrainSystem.cpp

@@ -222,20 +222,31 @@ float TerrainSystem::GetHeightSynchronous(float x, float y, Sampler sampler, boo
 
 float TerrainSystem::GetTerrainAreaHeight(float x, float y, bool& terrainExists) const
 {
-    AZ::Vector3 inPosition((float)x, (float)y, m_currentSettings.m_worldBounds.GetMin().GetZ());
-    float height = m_currentSettings.m_worldBounds.GetMin().GetZ();
+    const float worldMin = m_currentSettings.m_worldBounds.GetMin().GetZ();
+    AZ::Vector3 inPosition(x, y, worldMin);
+    float height = worldMin;
+    terrainExists = false;
 
     AZStd::shared_lock<AZStd::shared_mutex> lock(m_areaMutex);
 
-    for (auto& [areaId, areaBounds] : m_registeredAreas)
+    for (auto& [areaId, areaData] : m_registeredAreas)
     {
-        inPosition.SetZ(areaBounds.GetMin().GetZ());
-        if (areaBounds.Contains(inPosition))
+        const float areaMin = areaData.m_areaBounds.GetMin().GetZ();
+        inPosition.SetZ(areaMin);
+        if (areaData.m_areaBounds.Contains(inPosition))
         {
             AZ::Vector3 outPosition;
             Terrain::TerrainAreaHeightRequestBus::Event(
                 areaId, &Terrain::TerrainAreaHeightRequestBus::Events::GetHeight, inPosition, outPosition, terrainExists);
             height = outPosition.GetZ();
+            if (!terrainExists)
+            {
+                // If the terrain height provider doesn't have any data, then check the area's "use ground plane" setting.
+                // If it's set, then create a default ground plane by saying terrain exists at the minimum height for the area.
+                // Otherwise, we'll set the height at the terrain world minimum and say it doesn't exist.
+                terrainExists = areaData.m_useGroundPlane;
+                height = areaData.m_useGroundPlane ? areaMin : worldMin;
+            }
             break;
         }
     }
@@ -395,12 +406,12 @@ AZ::EntityId TerrainSystem::FindBestAreaEntityAtPosition(float x, float y, AZ::A
     AZStd::shared_lock<AZStd::shared_mutex> lock(m_areaMutex);
 
     // The areas are sorted into priority order: the first area that contains inPosition is the most suitable.
-    for (const auto& [areaId, areaBounds] : m_registeredAreas)
+    for (const auto& [areaId, areaData] : m_registeredAreas)
     {
-        inPosition.SetZ(areaBounds.GetMin().GetZ());
-        if (areaBounds.Contains(inPosition))
+        inPosition.SetZ(areaData.m_areaBounds.GetMin().GetZ());
+        if (areaData.m_areaBounds.Contains(inPosition))
         {
-            bounds = areaBounds;
+            bounds = areaData.m_areaBounds;
             return areaId;
         }
     }
@@ -548,7 +559,12 @@ void TerrainSystem::RegisterArea(AZ::EntityId areaId)
     AZStd::unique_lock<AZStd::shared_mutex> lock(m_areaMutex);
     AZ::Aabb aabb = AZ::Aabb::CreateNull();
     LmbrCentral::ShapeComponentRequestsBus::EventResult(aabb, areaId, &LmbrCentral::ShapeComponentRequestsBus::Events::GetEncompassingAabb);
-    m_registeredAreas[areaId] = aabb;
+
+    // Cache off whether or not this layer spawner should have a default ground plane when no other terrain height data exists.
+    bool useGroundPlane = false;
+    Terrain::TerrainSpawnerRequestBus::EventResult(useGroundPlane, areaId, &Terrain::TerrainSpawnerRequestBus::Events::GetUseGroundPlane);
+
+    m_registeredAreas[areaId] = { aabb, useGroundPlane };
     m_dirtyRegion.AddAabb(aabb);
     m_terrainHeightDirty = true;
     m_terrainSurfacesDirty = true;
@@ -565,10 +581,10 @@ void TerrainSystem::UnregisterArea(AZ::EntityId areaId)
         m_registeredAreas,
         [areaId, this](const auto& item)
         {
-            auto const& [entityId, aabb] = item;
+            auto const& [entityId, areaData] = item;
             if (areaId == entityId)
             {
-                m_dirtyRegion.AddAabb(aabb);
+                m_dirtyRegion.AddAabb(areaData.m_areaBounds);
                 m_terrainHeightDirty = true;
                 m_terrainSurfacesDirty = true;
                 return true;
@@ -585,10 +601,10 @@ void TerrainSystem::RefreshArea(AZ::EntityId areaId, AzFramework::Terrain::Terra
 
     auto areaAabb = m_registeredAreas.find(areaId);
 
-    AZ::Aabb oldAabb = (areaAabb != m_registeredAreas.end()) ? areaAabb->second : AZ::Aabb::CreateNull();
+    AZ::Aabb oldAabb = (areaAabb != m_registeredAreas.end()) ? areaAabb->second.m_areaBounds : AZ::Aabb::CreateNull();
     AZ::Aabb newAabb = AZ::Aabb::CreateNull();
     LmbrCentral::ShapeComponentRequestsBus::EventResult(newAabb, areaId, &LmbrCentral::ShapeComponentRequestsBus::Events::GetEncompassingAabb);
-    m_registeredAreas[areaId] = newAabb;
+    m_registeredAreas[areaId].m_areaBounds = newAabb;
 
     AZ::Aabb expandedAabb = oldAabb;
     expandedAabb.AddAabb(newAabb);

Gems/Terrain/Code/Source/TerrainSystem/TerrainSystem.h

@@ -168,7 +168,14 @@ namespace Terrain
         bool m_terrainSurfacesDirty = false;
         AZ::Aabb m_dirtyRegion;
 
+        // Cached data for each terrain area to use when looking up terrain data.
+        struct TerrainAreaData
+        {
+            AZ::Aabb m_areaBounds{ AZ::Aabb::CreateNull() };
+            bool m_useGroundPlane{ false };
+        };
+
         mutable AZStd::shared_mutex m_areaMutex;
-        AZStd::map<AZ::EntityId, AZ::Aabb, TerrainLayerPriorityComparator> m_registeredAreas;
+        AZStd::map<AZ::EntityId, TerrainAreaData, TerrainLayerPriorityComparator> m_registeredAreas;
     };
 } // namespace Terrain