From 79af7d3c0053eb4d7fc673c449ef65c8f594233b Mon Sep 17 00:00:00 2001
From: Yuriy Toporovskyy <toporovskyy.y@gmail.com>
Date: Thu, 5 Aug 2021 17:47:19 -0400
Subject: [PATCH] Make the maximum amount of vmem available for skinning
 related things configurable at runtime

Signed-off-by: Yuriy Toporovskyy <toporovskyy.y@gmail.com>
---
 .../SkinnedMeshOutputStreamManager.cpp        | 33 ++++++++++++++++++-
 .../SkinnedMeshOutputStreamManager.h          |  3 ++
 2 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/Gems/Atom/Feature/Common/Code/Source/SkinnedMesh/SkinnedMeshOutputStreamManager.cpp b/Gems/Atom/Feature/Common/Code/Source/SkinnedMesh/SkinnedMeshOutputStreamManager.cpp
index c4eac30431..ffbe850160 100644
--- a/Gems/Atom/Feature/Common/Code/Source/SkinnedMesh/SkinnedMeshOutputStreamManager.cpp
+++ b/Gems/Atom/Feature/Common/Code/Source/SkinnedMesh/SkinnedMeshOutputStreamManager.cpp
@@ -8,6 +8,8 @@
 
 #include <SkinnedMesh/SkinnedMeshOutputStreamManager.h>
 
+#include <AzCore/Console/IConsole.h>
+
 #include <Atom/Feature/SkinnedMesh/SkinnedMeshVertexStreams.h>
 #include <Atom/Feature/SkinnedMesh/SkinnedMeshFeatureProcessorBus.h>
 
@@ -72,11 +74,36 @@ namespace AZ
             creator.End(m_bufferAsset);
         }
 
+        AZ_CVAR(
+            int,
+            r_skinnedMeshInstanceMemoryPoolSize,
+            256,
+            nullptr,
+            AZ::ConsoleFunctorFlags::NeedsReload,
+            "The amount of memory in Mb available for all actor skinning data. Note that this must only be set once at application startup"
+        );
+
         void SkinnedMeshOutputStreamManager::Init()
         {
+        }
+
+        void SkinnedMeshOutputStreamManager::EnsureInit() const
+        {
+            const_cast<SkinnedMeshOutputStreamManager*>(this)->EnsureInit();
+        }
+
+        void SkinnedMeshOutputStreamManager::EnsureInit()
+        {
+            if (!m_needsInit)
+            {
+                return;
+            }
+            m_needsInit = false;
+
             // 256mb supports roughly 42 character instances at 100,000 vertices per character x 64 bytes per vertex (12 byte position + 12 byte previous frame position + 12 byte normal + 16 byte tangent + 12 byte bitangent)
             // This includes only the output of the skinning compute shader, not the input buffers or bone transforms
-            m_sizeInBytes = 256u * (1024u * 1024u);
+            const AZ::u64 sizeInMb = r_skinnedMeshInstanceMemoryPoolSize;
+            m_sizeInBytes = AZ::GetMax(sizeInMb, 256ull) * (1024u * 1024u);
 
             CalculateAlignment();
 
@@ -90,6 +117,8 @@ namespace AZ
             RHI::VirtualAddress result;
             {
                 AZStd::lock_guard<AZStd::mutex> lock(m_allocatorMutex);
+
+                EnsureInit();
                 result = m_freeListAllocator.Allocate(byteCount, m_alignment);
             }
 
@@ -129,11 +158,13 @@ namespace AZ
 
         Data::Asset<RPI::BufferAsset> SkinnedMeshOutputStreamManager::GetBufferAsset() const
         {
+            EnsureInit();
             return m_bufferAsset;
         }
 
         Data::Instance<RPI::Buffer> SkinnedMeshOutputStreamManager::GetBuffer()
         {
+            EnsureInit();
             if (!m_buffer)
             {
                 m_buffer = RPI::Buffer::FindOrCreate(m_bufferAsset);
diff --git a/Gems/Atom/Feature/Common/Code/Source/SkinnedMesh/SkinnedMeshOutputStreamManager.h b/Gems/Atom/Feature/Common/Code/Source/SkinnedMesh/SkinnedMeshOutputStreamManager.h
index 3cec34a2e2..6009a62362 100644
--- a/Gems/Atom/Feature/Common/Code/Source/SkinnedMesh/SkinnedMeshOutputStreamManager.h
+++ b/Gems/Atom/Feature/Common/Code/Source/SkinnedMesh/SkinnedMeshOutputStreamManager.h
@@ -46,6 +46,8 @@ namespace AZ
             // SystemTickBus
             void OnSystemTick() override;
 
+            void EnsureInit() const;
+            void EnsureInit();
             void GarbageCollect();
             void CalculateAlignment();
             void CreateBufferAsset();
@@ -58,6 +60,7 @@ namespace AZ
             size_t m_sizeInBytes = 0;
             bool m_memoryWasFreed = false;
             bool m_broadcastMemoryAvailableEvent = false;
+            bool m_needsInit = true;
         };
     } // namespace Render
 } // namespace AZ