From 18d8da09450bed533166076e36bc3e3f83e5e7a3 Mon Sep 17 00:00:00 2001
From: Steffen Ohrendorf <steffen.ohrendorf@gmx.de>
Date: Sat, 9 Oct 2021 12:17:43 +0200
Subject: [PATCH] use less blocking sync

---
 src/engine/presenter.cpp | 16 +++++++++++-----
 src/render/scene/csm.h   | 17 +++++++++++++++++
 2 files changed, 28 insertions(+), 5 deletions(-)

diff --git a/src/engine/presenter.cpp b/src/engine/presenter.cpp
index e86983a56..69781f5c9 100644
--- a/src/engine/presenter.cpp
+++ b/src/engine/presenter.cpp
@@ -123,8 +123,6 @@ void Presenter::renderWorld(const ObjectManager& objectManager,
 
     for(const auto& texture : m_csm->getDepthTextures())
       texture->clear(gl::ScalarDepth{1.0f});
-    gl::FenceSync::block();
-
     for(size_t i = 0; i < render::scene::CSMBuffer::NSplits; ++i)
     {
       SOGLB_DEBUGGROUP("csm-pass/" + std::to_string(i));
@@ -147,24 +145,32 @@ void Presenter::renderWorld(const ObjectManager& objectManager,
           visitor.visit(*child);
         }
       }
+      m_csm->beginActiveSync();
     }
-    gl::FenceSync::block();
 
     for(size_t i = 0; i < render::scene::CSMBuffer::NSplits; ++i)
     {
       SOGLB_DEBUGGROUP("csm-pass-square/" + std::to_string(i));
       m_csm->setActiveSplit(i);
+      m_csm->waitActiveSync();
       m_csm->renderSquare();
+      m_csm->beginActiveSync();
     }
-    gl::FenceSync::block();
 
     for(size_t i = 0; i < render::scene::CSMBuffer::NSplits; ++i)
     {
       SOGLB_DEBUGGROUP("csm-pass-blur/" + std::to_string(i));
       m_csm->setActiveSplit(i);
+      m_csm->waitActiveSync();
       m_csm->renderBlur();
+      m_csm->beginActiveSync();
+    }
+
+    for(size_t i = 0; i < render::scene::CSMBuffer::NSplits; ++i)
+    {
+      m_csm->setActiveSplit(i);
+      m_csm->waitActiveSync();
     }
-    gl::FenceSync::block();
   }
 
   {
diff --git a/src/render/scene/csm.h b/src/render/scene/csm.h
index f96f5e555..df39b2a67 100644
--- a/src/render/scene/csm.h
+++ b/src/render/scene/csm.h
@@ -8,6 +8,7 @@
 #include <cstddef>
 #include <cstdint>
 #include <gl/buffer.h>
+#include <gl/fencesync.h>
 #include <gl/pixel.h>
 #include <gl/renderstate.h>
 #include <gl/soglb_fwd.h>
@@ -49,6 +50,7 @@ class CSM final
     std::shared_ptr<Material> squareMaterial{};
     std::shared_ptr<Mesh> squareMesh{};
     std::shared_ptr<SeparableBlur<gl::RG16F>> squareBlur;
+    mutable std::unique_ptr<gl::FenceSync> sync;
 
     void init(int32_t resolution, size_t idx, MaterialManager& materialManager);
     void renderSquare();
@@ -74,6 +76,21 @@ class CSM final
     return m_splits.at(m_activeSplit).depthFramebuffer;
   }
 
+  void beginActiveSync() const
+  {
+    m_splits.at(m_activeSplit).sync = std::make_unique<gl::FenceSync>();
+  }
+
+  void waitActiveSync() const
+  {
+    auto& sync = m_splits.at(m_activeSplit).sync;
+    if(sync == nullptr)
+      return;
+    
+    sync->wait();
+    sync.reset();
+  }
+
   void setActiveSplit(size_t idx)
   {
     Expects(idx < m_splits.size());