From c8082104db804f9a6320ff0d79f8976d7dadd08e Mon Sep 17 00:00:00 2001
From: fleroviux <fleroviux@gmail.com>
Date: Wed, 1 May 2024 13:33:16 +0200
Subject: [PATCH] Zephyr: Renderer: introduce intermediate game thread render
 objects

---
 .../include/zephyr/renderer/render_engine.hpp |  8 +++++
 zephyr/renderer/src/render_engine.cpp         | 33 +++++++++++++------
 2 files changed, 31 insertions(+), 10 deletions(-)

diff --git a/zephyr/renderer/include/zephyr/renderer/render_engine.hpp b/zephyr/renderer/include/zephyr/renderer/render_engine.hpp
index 6497545..8c4d263 100644
--- a/zephyr/renderer/include/zephyr/renderer/render_engine.hpp
+++ b/zephyr/renderer/include/zephyr/renderer/render_engine.hpp
@@ -3,6 +3,7 @@
 
 #include <zephyr/math/matrix4.hpp>
 #include <zephyr/renderer/backend/render_backend.hpp>
+#include <zephyr/renderer/resource/geometry.hpp>
 #include <zephyr/scene/node.hpp>
 #include <atomic>
 #include <semaphore>
@@ -22,6 +23,7 @@ namespace zephyr {
       void CreateRenderThread();
       void JoinRenderThread();
       void RenderThreadMain();
+      void ReadyRenderThreadData();
 
       std::shared_ptr<RenderBackend> m_render_backend;
 
@@ -31,6 +33,12 @@ namespace zephyr {
       std::binary_semaphore m_caller_thread_semaphore{0}; //> Semaphore signalled by the calling thread
       std::binary_semaphore m_render_thread_semaphore{1}; //> Semaphore signalled by the rendering thread
 
+      struct GameThreadRenderObject {
+        Matrix4 local_to_world;
+        Geometry* geometry;
+      };
+      std::vector<GameThreadRenderObject> m_game_thread_render_objects;
+
       std::vector<RenderObject> m_render_objects;
   };
 
diff --git a/zephyr/renderer/src/render_engine.cpp b/zephyr/renderer/src/render_engine.cpp
index b896343..e2b794f 100644
--- a/zephyr/renderer/src/render_engine.cpp
+++ b/zephyr/renderer/src/render_engine.cpp
@@ -18,7 +18,7 @@ namespace zephyr {
     // Wait for the render thread to complete reading the internal render structures.
     m_render_thread_semaphore.acquire();
 
-    m_render_objects.clear();
+    m_game_thread_render_objects.clear();
 
     scene_root->Traverse([&](SceneNode* node) -> bool {
       if(!node->IsVisible()) return false;
@@ -28,8 +28,9 @@ namespace zephyr {
         const auto& geometry = mesh_component.geometry;
 
         if(geometry) {
-          m_render_objects.push_back({
-            .local_to_world = node->GetTransform().GetWorld()
+          m_game_thread_render_objects.push_back({
+            .local_to_world = node->GetTransform().GetWorld(),
+            .geometry = geometry.get()
           });
         }
       }
@@ -59,21 +60,33 @@ namespace zephyr {
     m_render_backend->InitializeContext();
 
     while(m_render_thread_running) {
-      // Wait for the caller thread to prepare the internal render structures for the next frame.
-      m_render_thread_is_waiting = true;
-      m_caller_thread_semaphore.acquire();
-      m_render_thread_is_waiting = false;
+      ReadyRenderThreadData();
 
       // TODO(fleroviux): do not hardcode the aspect ratio.
       const Matrix4 projection = Matrix4::PerspectiveVK(45.0f, 16.0f/9.0, 0.01f, 100.0f);
       m_render_backend->Render(projection, m_render_objects);
       m_render_backend->SwapBuffers();
-
-      // Signal to the caller thread that we are done reading the internal render structures.
-      m_render_thread_semaphore.release();
     }
 
     m_render_backend->DestroyContext();
   }
 
+  void RenderEngine::ReadyRenderThreadData() {
+    // Wait for the caller thread to prepare the internal render structures for the next frame.
+    m_render_thread_is_waiting = true;
+    m_caller_thread_semaphore.acquire();
+    m_render_thread_is_waiting = false;
+
+    m_render_objects.clear();
+
+    for(const auto& game_thread_render_object : m_game_thread_render_objects) {
+      m_render_objects.push_back({
+        .local_to_world = game_thread_render_object.local_to_world
+      });
+    }
+
+    // Signal to the caller thread that we are done reading the internal render structures.
+    m_render_thread_semaphore.release();
+  }
+
 } // namespace zephyr
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