Add stencil test + split object and camera velocity

ScriptableRenderPipeline/HDRenderPipeline/HDRenderPipeline.cs

         public enum StencilBitMask
         {
             Clear    = 0,                    // 0x0
-            Lighting = 3,                    // 0x3  - 2 bit
+            Lighting = 7,                    // 0x7  - 3 bit
+            ObjectVelocity = 128,            // 1 bit
             All      = 255                   // 0xFF - 8 bit
         }
 
 
                     RenderDepthPrepass(m_CullResults, hdCamera, renderContext, cmd, true);
 
-                    RenderVelocity(m_CullResults, hdCamera, renderContext, cmd);
+                    RenderObjectsVelocity(m_CullResults, hdCamera, renderContext, cmd);
 
                     RenderDBuffer(hdCamera.cameraPos, renderContext, cmd);
 
                     CopyDepthBufferIfNeeded(cmd);
+
+                    RenderCameraVelocity(m_CullResults, hdCamera, renderContext, cmd);
 
                     // Depth texture is now ready, bind it.
                     cmd.SetGlobalTexture(HDShaderIDs._MainDepthTexture, GetDepthTexture());
             }
         }
 
-        void RenderVelocity(CullResults cullResults, HDCamera hdcam, ScriptableRenderContext renderContext, CommandBuffer cmd)
+        void RenderObjectsVelocity(CullResults cullResults, HDCamera hdcam, ScriptableRenderContext renderContext, CommandBuffer cmd)
         {
             if (!m_FrameSettings.enableMotionVectors || !m_FrameSettings.enableObjectMotionVectors)
                 return;
                 int w = (int)hdcam.screenSize.x;
                 int h = (int)hdcam.screenSize.y;
 
+                cmd.SetRenderTarget(m_VelocityBufferRT, m_CameraDepthStencilBufferRT);
+
+                RenderOpaqueRenderList(cullResults, hdcam.camera, renderContext, cmd, HDShaderPassNames.s_MotionVectorsName, RendererConfiguration.PerObjectMotionVectors);
+            }
+        }
+
+        void RenderCameraVelocity(CullResults cullResults, HDCamera hdcam, ScriptableRenderContext renderContext, CommandBuffer cmd)
+        {
+            if (!m_FrameSettings.enableMotionVectors)
+                return;
+
+            using (new ProfilingSample(cmd, "Velocity", GetSampler(CustomSamplerId.Velocity)))
+            {
+                // These flags are still required in SRP or the engine won't compute previous model matrices...
+                // If the flag hasn't been set yet on this camera, motion vectors will skip a frame.
+                hdcam.camera.depthTextureMode |= DepthTextureMode.MotionVectors | DepthTextureMode.Depth;
+
+                int w = (int)hdcam.screenSize.x;
+                int h = (int)hdcam.screenSize.y;
+
+                // TODO: This is not safe ? as we don't use cmd buffer we can have a dealy no ?
-                cmd.SetRenderTarget(m_VelocityBufferRT, m_CameraDepthStencilBufferRT);
-
-                RenderOpaqueRenderList(cullResults, hdcam.camera, renderContext, cmd, HDShaderPassNames.s_MotionVectorsName, RendererConfiguration.PerObjectMotionVectors);
 
                 PushFullScreenDebugTexture(cmd, m_VelocityBuffer, hdcam.camera, renderContext, FullScreenDebugMode.MotionVectors);
             }
                     }
 
                     m_DbufferManager.InitDBuffers(w, h, cmd);
+
+                    if (m_FrameSettings.enableMotionVectors || m_FrameSettings.enableObjectMotionVectors)
+                    {
+                        // Note: We don't need to clear this buffer, it will be fill entirely by the rendering into the velocity buffer
+                        cmd.ReleaseTemporaryRT(m_VelocityBuffer);
+                        cmd.GetTemporaryRT(m_VelocityBuffer, w, h, 0, FilterMode.Point, Builtin.GetVelocityBufferFormat(), Builtin.GetVelocityBufferReadWrite());
+                    }
 
                     CoreUtils.SetRenderTarget(cmd, m_CameraColorBufferRT, m_CameraDepthStencilBufferRT, ClearFlag.Depth);
                 }

ScriptableRenderPipeline/HDRenderPipeline/Material/Lit/Lit.shader

             Name "Motion Vectors"
             Tags{ "LightMode" = "MotionVectors" } // Caution, this need to be call like this to setup the correct parameters by C++ (legacy Unity)
 
+            // If velocity pass (motion vectors) is enabled we tag the stencil so it don't perform CameraMotionVelocity
+            Stencil
+            {
+                Ref  128 // StencilBitMask.ObjectVelocity
+                Comp Always
+                Pass Replace
+            }
+
             Cull[_CullMode]
 
             ZWrite Off // TODO: Test Z equal here.

ScriptableRenderPipeline/HDRenderPipeline/RenderPipelineResources/CameraMotionVectors.shader

 
     SubShader
     {
-        Cull Off ZWrite Off ZTest Always
-
+            // We will perform camera motion velocity only where there is no object velocity
+            Stencil
+            {
+                Ref  128 // StencilBitMask.ObjectVelocity
+                Comp NotEqual
+                Pass Keep
+            }
+
+            Cull Off ZWrite Off ZTest Always
+
             HLSLPROGRAM
 
                 #pragma vertex Vert