Merge pull request #5328 from aws-lumberyard-dev/terrain/mbalfour/altitude_gradient_infinite_recursion_bug

Prevent infinite recursion with Altitude Gradient.

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

@@ -151,24 +151,29 @@ namespace Terrain
     {
         float maxSample = 0.0f;
         terrainExists = false;
-
-        GradientSignal::GradientSampleParams params(AZ::Vector3(inPosition.GetX(), inPosition.GetY(), 0.0f));
-
-        // Right now, when the list contains multiple entries, we will use the highest point from each gradient.
-        // This is needed in part because gradients don't really have world bounds, so they exist everywhere but generally have a value
-        // of 0 outside their data bounds if they're using bounded data.  We should examine the possibility of extending the gradient API
-        // to provide actual bounds so that it's possible to detect if the gradient even 'exists' in an area, at which point we could just
-        // make this list a prioritized list from top to bottom for any points that overlap.
-        for (auto& gradientId : m_configuration.m_gradientEntities)
+        AZ_WarningOnce("Terrain", !m_isRequestInProgress, "Detected cyclic dependences with terrain height entity references");
+        if (!m_isRequestInProgress)
         {
-            // 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;
+            m_isRequestInProgress = true;
+            GradientSignal::GradientSampleParams params(AZ::Vector3(inPosition.GetX(), inPosition.GetY(), 0.0f));
 
-            float sample = 0.0f;
-            GradientSignal::GradientRequestBus::EventResult(
-                sample, gradientId, &GradientSignal::GradientRequestBus::Events::GetValue, params);
-            maxSample = AZ::GetMax(maxSample, sample);
+            // Right now, when the list contains multiple entries, we will use the highest point from each gradient.
+            // This is needed in part because gradients don't really have world bounds, so they exist everywhere but generally have a value
+            // of 0 outside their data bounds if they're using bounded data.  We should examine the possibility of extending the gradient
+            // API to provide actual bounds so that it's possible to detect if the gradient even 'exists' in an area, at which point we
+            // 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;
+
+                float sample = 0.0f;
+                GradientSignal::GradientRequestBus::EventResult(
+                    sample, gradientId, &GradientSignal::GradientRequestBus::Events::GetValue, params);
+                maxSample = AZ::GetMax(maxSample, sample);
+            }
+            m_isRequestInProgress = false;
         }
 
         const float height = AZ::Lerp(m_cachedShapeBounds.GetMin().GetZ(), m_cachedShapeBounds.GetMax().GetZ(), maxSample);

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

@@ -91,6 +91,9 @@ namespace Terrain
         AZ::Vector2 m_cachedHeightQueryResolution{ 1.0f, 1.0f };
         AZ::Aabb m_cachedShapeBounds;
 
+        // prevent recursion in case user attaches cyclic dependences
+        mutable bool m_isRequestInProgress{ false }; 
+
         LmbrCentral::DependencyMonitor m_dependencyMonitor;
     };
 }