Reenable LyShine mask support now using Atom (#1218)

* Add option to set stencil ref in Dynamic Draw Context

* Add depth/stencil attachment slot to UI pass

* Rework mask rendering to use Atom

* Add missing circle mask image

Gems/Atom/RPI/Code/Include/Atom/RPI.Public/DynamicDraw/DynamicDrawContext.h

@@ -138,6 +138,12 @@ namespace AZ
             //! Without per draw viewport, the viewport setup in pass is usually used. 
             void UnsetViewport();
 
+            //! Set stencil reference for following draws which are added to this DynamicDrawContext
+            void SetStencilReference(uint8_t stencilRef);
+
+            //! Get the current stencil reference.
+            uint8_t GetStencilReference() const;
+
             //! Draw Indexed primitives with vertex and index data and per draw srg
             //! The per draw srg need to be provided if it's required by shader. 
             void DrawIndexed(void* vertexData, uint32_t vertexCount, void* indexData, uint32_t indexCount, RHI::IndexFormat indexFormat, Data::Instance < ShaderResourceGroup> drawSrg = nullptr);
@@ -204,10 +210,13 @@ namespace AZ
             bool m_useScissor = false;
             RHI::Scissor m_scissor;
 
-            // current scissor
+            // current viewport
             bool m_useViewport = false;
             RHI::Viewport m_viewport;
 
+            // Current stencil reference value
+            uint8_t m_stencilRef = 0;
+
             // Cached RHI pipeline states for different combination of render states 
             AZStd::unordered_map<HashValue64, const RHI::PipelineState*> m_cachedRhiPipelineStates;
 

Gems/Atom/RPI/Code/Source/RPI.Public/DynamicDraw/DynamicDrawContext.cpp

@@ -382,6 +382,16 @@ namespace AZ
             m_useViewport = false;
         }
 
+        void DynamicDrawContext::SetStencilReference(uint8_t stencilRef)
+        {
+            m_stencilRef = stencilRef;
+        }
+
+        uint8_t DynamicDrawContext::GetStencilReference() const
+        {
+            return m_stencilRef;
+        }
+
         void DynamicDrawContext::SetShaderVariant(ShaderVariantId shaderVariantId)
         {
             AZ_Assert( m_initialized && m_supportShaderVariants, "DynamicDrawContext is not initialized or unable to support shader variants. "
@@ -475,6 +485,9 @@ namespace AZ
                 drawItem.m_viewports = &m_viewport;
             }
 
+            // Set stencil reference. Used when stencil is enabled.
+            drawItem.m_stencilRef = m_stencilRef;
+
             drawItemInfo.m_sortKey = m_sortKey++;
             m_cachedDrawItems.emplace_back(drawItemInfo);
         }