From 31b5685251186f1b71ea1c089f1852e34380fa5f Mon Sep 17 00:00:00 2001
From: Wojtek Figat <wojtek@figat.pl>
Date: Fri, 20 Feb 2026 23:45:56 +0100
Subject: [PATCH] Add `GPU_ENABLE_PRELOADING_RESOURCES` and use it on
 Web/Android/iOS to reduce engine resources preloading

---
 Source/Engine/Graphics/Config.h               |  5 +++++
 .../Engine/Platform/Android/AndroidDefines.h  |  1 +
 Source/Engine/Platform/Web/WebDefines.h       |  1 +
 Source/Engine/Platform/iOS/iOSDefines.h       |  1 +
 Source/Engine/Renderer/Renderer.cpp           |  2 ++
 Source/Engine/Renderer/RendererPass.h         | 12 ++++++++++--
 Source/Engine/Terrain/TerrainManager.cpp      | 19 ++++++++++++-------
 7 files changed, 32 insertions(+), 9 deletions(-)

diff --git a/Source/Engine/Graphics/Config.h b/Source/Engine/Graphics/Config.h
index 2059fb0a9..cd734ab98 100644
--- a/Source/Engine/Graphics/Config.h
+++ b/Source/Engine/Graphics/Config.h
@@ -64,6 +64,11 @@
 #define GPU_ENABLE_ASYNC_RESOURCES_CREATION 1
 #endif
 
+// Enable/disable preloading GPU resources (eg. shaders, default assets)
+#ifndef GPU_ENABLE_PRELOADING_RESOURCES
+#define GPU_ENABLE_PRELOADING_RESOURCES 1
+#endif
+
 // Enable/disable force shaders recompilation
 #define GPU_FORCE_RECOMPILE_SHADERS 0
 
diff --git a/Source/Engine/Platform/Android/AndroidDefines.h b/Source/Engine/Platform/Android/AndroidDefines.h
index 15f3b030b..490bdb964 100644
--- a/Source/Engine/Platform/Android/AndroidDefines.h
+++ b/Source/Engine/Platform/Android/AndroidDefines.h
@@ -38,5 +38,6 @@
 
 #define GPU_ALLOW_TESSELLATION_SHADERS 0 // Tess on mobile is not well supported
 #define GPU_ALLOW_GEOMETRY_SHADERS 0 // Don't even try GS on mobile
+#define GPU_ENABLE_PRELOADING_RESOURCES 0 // Don't preload things unless needed
 
 #endif
diff --git a/Source/Engine/Platform/Web/WebDefines.h b/Source/Engine/Platform/Web/WebDefines.h
index edfff3c04..3f8900b2b 100644
--- a/Source/Engine/Platform/Web/WebDefines.h
+++ b/Source/Engine/Platform/Web/WebDefines.h
@@ -18,6 +18,7 @@
 #define GPU_ALLOW_TESSELLATION_SHADERS 0
 #define GPU_ALLOW_GEOMETRY_SHADERS 0
 #define GPU_ALLOW_PROFILE_EVENTS 0
+#define GPU_ENABLE_PRELOADING_RESOURCES 0 // Don't preload things unless needed
 
 // Threading is optional
 #ifdef __EMSCRIPTEN_PTHREADS__
diff --git a/Source/Engine/Platform/iOS/iOSDefines.h b/Source/Engine/Platform/iOS/iOSDefines.h
index 8e0530634..0106620da 100644
--- a/Source/Engine/Platform/iOS/iOSDefines.h
+++ b/Source/Engine/Platform/iOS/iOSDefines.h
@@ -21,5 +21,6 @@
 
 #define GPU_ALLOW_TESSELLATION_SHADERS 0 // MoltenVK has artifacts when using tess so disable it
 #define GPU_ALLOW_GEOMETRY_SHADERS 0 // Don't even try GS on mobile
+#define GPU_ENABLE_PRELOADING_RESOURCES 0 // Don't preload things unless needed
 
 #endif
diff --git a/Source/Engine/Renderer/Renderer.cpp b/Source/Engine/Renderer/Renderer.cpp
index 7ba267745..ddbb8573e 100644
--- a/Source/Engine/Renderer/Renderer.cpp
+++ b/Source/Engine/Renderer/Renderer.cpp
@@ -105,6 +105,7 @@ bool RendererService::Init()
         return false;
     }
 
+#if GPU_ENABLE_PRELOADING_RESOURCES
     // Init child services
     for (int32 i = 0; i < PassList.Count(); i++)
     {
@@ -114,6 +115,7 @@ bool RendererService::Init()
             return true;
         }
     }
+#endif
 
     return false;
 }
diff --git a/Source/Engine/Renderer/RendererPass.h b/Source/Engine/Renderer/RendererPass.h
index fee05e302..49f79328d 100644
--- a/Source/Engine/Renderer/RendererPass.h
+++ b/Source/Engine/Renderer/RendererPass.h
@@ -21,7 +21,9 @@
 class FLAXENGINE_API RendererPassBase : public Object
 {
 protected:
-
+#if !GPU_ENABLE_PRELOADING_RESOURCES
+    bool _lazyInit = true;
+#endif
     bool _hasValidResources;
 
     /// <summary>
@@ -66,7 +68,13 @@ protected:
     {
         if (_hasValidResources)
             return false;
-
+#if !GPU_ENABLE_PRELOADING_RESOURCES
+        if (_lazyInit)
+        {
+            _lazyInit = false;
+            Init();
+        }
+#endif
         const bool setupFailed = setupResources();
         _hasValidResources = !setupFailed;
         return setupFailed;
diff --git a/Source/Engine/Terrain/TerrainManager.cpp b/Source/Engine/Terrain/TerrainManager.cpp
index 6da020079..1c8da1748 100644
--- a/Source/Engine/Terrain/TerrainManager.cpp
+++ b/Source/Engine/Terrain/TerrainManager.cpp
@@ -68,6 +68,15 @@ TerrainManagerService TerrainManagerServiceInstance;
 
 MaterialBase* TerrainManager::GetDefaultTerrainMaterial()
 {
+    if (!DefaultTerrainMaterial)
+    {
+        // Load default terrain material as fallback
+        DefaultTerrainMaterial = Content::LoadAsyncInternal<MaterialBase>(TEXT("Engine/DefaultTerrainMaterial"));
+        if (DefaultTerrainMaterial == nullptr)
+        {
+            LOG(Warning, "Default terrain material is missing.");
+        }
+    }
     return DefaultTerrainMaterial.Get();
 }
 
@@ -221,13 +230,9 @@ bool TerrainManager::GetChunkGeometry(DrawCall& drawCall, int32 chunkSize, int32
 
 bool TerrainManagerService::Init()
 {
-    // Load default terrain material as fallback
-    DefaultTerrainMaterial = Content::LoadAsyncInternal<MaterialBase>(TEXT("Engine/DefaultTerrainMaterial"));
-    if (DefaultTerrainMaterial == nullptr)
-    {
-        LOG(Warning, "Default terrain material is missing.");
-    }
-
+#if GPU_ENABLE_PRELOADING_RESOURCES
+    TerrainManager::GetDefaultTerrainMaterial();
+#endif
     return false;
 }