Add FullscreenPassthrough render mode

ScriptableRenderPipeline/HDRenderPipeline/HDRP/Camera/HDAdditionalCameraData.cs

         // Default is the default rendering path define by the HDRendeRPipelineAsset FrameSettings.
         // Custom allow users to define the FrameSettigns for this path
         // Then enum can contain either preset of FrameSettings or hard coded path
-        // Unlit below is a hard coded path (a path that can't be implemented only with FrameSettings)
+        // FullscreenPassthrough below is a hard coded path (a path that can't be implemented only with FrameSettings)
-            Unlit  // Hard coded path
+            FullscreenPassthrough  // Hard coded path
         };
 
         public enum ClearColorMode
 
         void UnRegisterDebug()
         {
-            if (m_camera == null) 
+            if (m_camera == null)
                 return;
 
             if (m_IsDebugRegistered)
             // When LDR, unity render in 8bitSRGB, then do a final shader with sRGB conversion
             // What should be done is just in our Post process we convert to sRGB and store in a linear 10bit, but require C++ change...
             m_camera = GetComponent<Camera>();
-            if (m_camera == null) 
+            if (m_camera == null)
-                
+
             m_camera.allowHDR = false;
 
             //  Tag as dirty so frameSettings are correctly initialize at next HDRenderPipeline.Render() call

ScriptableRenderPipeline/HDRenderPipeline/HDRP/HDRenderPipeline.cs

 
                 RenderPipeline.BeginCameraRendering(camera);
 
-                if (camera.cameraType != CameraType.Reflection)
-                    // TODO: Render only visible probes
-                    ReflectionSystem.RenderAllRealtimeViewerDependentProbesFor(ReflectionProbeType.PlanarReflection, camera);
-
                 // First, get aggregate of frame settings base on global settings, camera frame settings and debug settings
                 // Note: the SceneView camera will never have additionalCameraData
                 var additionalCameraData = camera.GetComponent<HDAdditionalCameraData>();
 
                 // This is the main command buffer used for the frame.
                 var cmd = CommandBufferPool.Get("");
+
+                // Specific pass to simply display the content of the camera buffer if users have fill it themselves (like video player)
+                if (additionalCameraData && additionalCameraData.renderingPath == HDAdditionalCameraData.RenderingPath.FullscreenPassthrough)
+                {
+                    renderContext.ExecuteCommandBuffer(cmd);
+                    CommandBufferPool.Release(cmd);
+                    renderContext.Submit();
+                    continue;
+                }
+
+                if (camera.cameraType != CameraType.Reflection)
+                    // TODO: Render only visible probes
+                    ReflectionSystem.RenderAllRealtimeViewerDependentProbesFor(ReflectionProbeType.PlanarReflection, camera);
 
                 // Init material if needed
                 // TODO: this should be move outside of the camera loop but we have no command buffer, ask details to Tim or Julien to do this
                     // TODO: Find a correct place to bind these material textures
                     // We have to bind the material specific global parameters in this mode
                     m_MaterialList.ForEach(material => material.Bind());
-
-                    if (additionalCameraData && additionalCameraData.renderingPath == HDAdditionalCameraData.RenderingPath.Unlit)
-                    {
-                        // TODO: Add another path dedicated to planar reflection / real time cubemap that implement simpler lighting
-                        // It is up to the users to only send unlit object for this camera path
-
-                        using (new ProfilingSample(cmd, "Forward", CustomSamplerId.Forward.GetSampler()))
-                        {
-                            HDUtils.SetRenderTarget(cmd, hdCamera, m_CameraColorBuffer, m_CameraDepthStencilBuffer, ClearFlag.Color | ClearFlag.Depth);
-                            RenderOpaqueRenderList(m_CullResults, camera, renderContext, cmd, HDShaderPassNames.s_ForwardName);
-                            RenderTransparentRenderList(m_CullResults, camera, renderContext, cmd, HDShaderPassNames.s_ForwardName);
-                        }
-
-                        renderContext.ExecuteCommandBuffer(cmd);
-                        CommandBufferPool.Release(cmd);
-                        renderContext.Submit();
-                        continue;
-                    }
 
                     // Frustum cull density volumes on the CPU. Can be performed as soon as the camera is set up.
                     DensityVolumeList densityVolumes = m_VolumetricLightingSystem.PrepareVisibleDensityVolumeList(hdCamera, cmd);
                     // During rendering we use our own depth buffer instead of the one provided by the scene view (because we need to be able to control its life cycle)
                     // In order for scene view gizmos/icons etc to be depth test correctly, we need to copy the content of our own depth buffer into the scene view depth buffer.
                     // On subtlety here is that our buffer can be bigger than the camera one so we need to copy only the corresponding portion
-                    // (it's handled automatically by the copy shader because it uses a load in pxiel coordinates based on the target).
+                    // (it's handled automatically by the copy shader because it uses a load in pixel coordinates based on the target).
                     // This copy will also have the effect of re-binding this depth buffer correctly for subsequent editor rendering.
 
                     // NOTE: This needs to be done before the call to RenderDebug because debug overlays need to update the depth for the scene view as well.