addressed PR feedback

Signed-off-by: antonmic <56370189+antonmic@users.noreply.github.com>
2021-12-16 10:42:53 -08:00
parent 18bb69a5cb
commit 2bc381811d
6 changed files with 21 additions and 6 deletions
@@ -65,8 +65,8 @@
                "Path": "Passes/CascadedShadowmaps.pass"
            },
            {
-                "Name": "ClearPassTemplate",
-                "Path": "Passes/Clear.pass"
+                "Name": "SlowClearPassTemplate",
+                "Path": "Passes/SlowClear.pass"
            },
            {
                "Name": "FullscreenCopyTemplate",
@@ -4,7 +4,11 @@
    "ClassName": "PassAsset",
    "ClassData": {
        "PassTemplate": {
-            "Name": "ClearPassTemplate",
+
+            // This is for debug purposes and edge cases only
+            // If you want to clear an attachment you should 
+            // use the LoadStoreAction on your pass slot.
+            "Name": "SlowClearPassTemplate",
            "PassClass": "ClearPass",
            "Slots": [
                {
@@ -86,7 +86,6 @@ set(FILES
    Passes/CascadedShadowmaps.pass
    Passes/CheckerboardResolveColor.pass
    Passes/CheckerboardResolveDepth.pass
-    Passes/Clear.pass
    Passes/ContrastAdaptiveSharpening.pass
    Passes/ConvertToAcescg.pass
    Passes/DebugOverlayParent.pass
@@ -201,6 +200,7 @@ set(FILES
    Passes/Skinning.pass
    Passes/SkyBox.pass
    Passes/SkyBox_TwoOutputs.pass
+    Passes/SlowClear.pass
    Passes/SMAA1xApplyLinearHDRColor.pass
    Passes/SMAA1xApplyPerceptualColor.pass
    Passes/SMAABlendingWeightCalculation.pass
@@ -14,7 +14,9 @@ namespace AZ
 {
    namespace RPI
    {
-        //! A simple pass to clear a render target
+        //! Only use this for debug purposes and edge cases
+        //! The correct and efficient way to clear a pass is through the LoadStoreAction on the pass slot
+        //! This will clear a given image attachment to the specified clear value.
        class ClearPass
            : public RenderPass
        {
@@ -133,6 +133,15 @@ namespace AZ
            void CreatePassesFromTemplate();

            // Generates child clear passes to clear input and input/output attachments
+            // TODO: These two functions are a workaround for a complicated edge case:
+            // Let Parent Pass P1 have two children, C1 and C2. C1 writes to an attachment that C2 reads,
+            // but C1 can be disabled, in which case we just want C2 to read the cleared texture.
+            // Because of this, the attachment is owned by the parent pass, that way it is always available for C2
+            // to read even when C1 is disabled. However we still want to clear the attachment before C2 reads it.
+            // We tried overriding the LoadStoreAction to clear on C2's slot when C1 is disabled, but the RHI 
+            // doesn't allow for clears on Input only slots. Changing the slot to InputOutput was in conflict with
+            // the texture definition in the SRG, and it couldn't be changed to RW because it was an MSAA texture.
+            // So now we detect clear actions on parent slots and generate a clear pass for them.
            void CreateClearPassFromBinding(PassAttachmentBinding& binding, PassRequest& clearRequest);
            void CreateClearPassesFromBindings();
        };
@@ -247,7 +247,7 @@ namespace AZ
        void ParentPass::CreateClearPassesFromBindings()
        {
            PassRequest clearRequest;
-            clearRequest.m_templateName = Name("ClearPassTemplate");
+            clearRequest.m_templateName = Name("SlowClearPassTemplate");
            clearRequest.m_passData = AZStd::make_shared<ClearPassData>();
            clearRequest.m_connections.push_back();
            clearRequest.m_connections[0].m_localSlot = Name("ClearInputOutput");