Merge pull request #1372 from Unity-Technologies/lw/fix-nested-camera-rendering

Add code to prevent nested camera rendering.

ScriptableRenderPipeline/LightweightPipeline/LWRP/LightweightPipeline.cs

         CullResults m_CullResults;
         List<int> m_LocalLightIndices = new List<int>();
 
+        bool m_IsCameraRendering;
+
         public LightweightPipeline(LightweightPipelineAsset asset)
         {
             pipelineAsset = asset;
                 QualitySettings.antiAliasing = pipelineAsset.MsaaSampleCount;
 
             Shader.globalRenderPipeline = "LightweightPipeline";
+            m_IsCameraRendering = false;
         }
 
         public override void Dispose()
 
         public override void Render(ScriptableRenderContext context, Camera[] cameras)
         {
+            if (m_IsCameraRendering)
+            {
+                Debug.LogWarning("Nested camera rendering is forbidden. If you are calling camera.Render inside OnWillRenderObject callback, use BeginCameraRender callback instead.");
+                return;
+            }
+
             base.Render(context, cameras);
             BeginFrameRendering(cameras);
 
             // Sort cameras array by camera depth
             Array.Sort(cameras, m_CameraComparer);
-
+            
+                BeginCameraRendering(camera);
+                m_IsCameraRendering = true;
+
-
-                BeginCameraRendering(camera);
-
+                
                 ScriptableCullingParameters cullingParameters;
                 if (!CullResults.GetCullingParameters(camera, cameraData.isStereoEnabled, out cullingParameters))
                     continue;
                 m_Renderer.Setup(ref context, ref m_CullResults, ref renderingData);
                 m_Renderer.Execute(ref context, ref m_CullResults, ref renderingData);
                 context.Submit();
+
+                m_IsCameraRendering = false;
+
         }
 
         void InitializeCameraData(Camera camera, out CameraData cameraData)