buffer update opt: Add engine config for default shared Ubo size (#9340)

android/filament-android/src/main/cpp/Engine.cpp

@@ -557,7 +557,8 @@ extern "C" JNIEXPORT void JNICALL Java_com_google_android_filament_Engine_nSetBu
         jboolean disableHandleUseAfterFreeCheck,
         jint preferredShaderLanguage,
         jboolean forceGLES2Context, jboolean assertNativeWindowIsValid,
-        jint gpuContextPriority) {
+        jint gpuContextPriority,
+        jlong sharedUboInitialSizeInBytes) {
     Engine::Builder* builder = (Engine::Builder*) nativeBuilder;
     Engine::Config config = {
             .commandBufferSizeMB = (uint32_t) commandBufferSizeMB,
@@ -576,6 +577,7 @@ extern "C" JNIEXPORT void JNICALL Java_com_google_android_filament_Engine_nSetBu
             .forceGLES2Context = (bool) forceGLES2Context,
             .assertNativeWindowIsValid = (bool) assertNativeWindowIsValid,
             .gpuContextPriority = (Engine::GpuContextPriority) gpuContextPriority,
+            .sharedUboInitialSizeInBytes = (uint32_t) sharedUboInitialSizeInBytes,
     };
     builder->config(&config);
 }

android/filament-android/src/main/java/com/google/android/filament/Engine.java

@@ -264,7 +264,8 @@ public class Engine {
                     config.disableHandleUseAfterFreeCheck,
                     config.preferredShaderLanguage.ordinal(),
                     config.forceGLES2Context, config.assertNativeWindowIsValid,
-                    config.gpuContextPriority.ordinal());
+                    config.gpuContextPriority.ordinal(),
+                    config.sharedUboInitialSizeInBytes);
             return this;
         }
 
@@ -525,6 +526,16 @@ public class Engine {
          * GPU context priority level. Controls GPU work scheduling and preemption.
          */
         public GpuContextPriority gpuContextPriority = GpuContextPriority.DEFAULT;
+
+        /**
+         * The initial size in bytes of the shared uniform buffer used for material instance batching.
+         *
+         * If the buffer runs out of space during a frame, it will be automatically reallocated
+         * with a larger capacity. Setting an appropriate initial size can help avoid runtime
+         * reallocations, which can cause a minor performance stutter, at the cost of higher
+         * initial memory usage.
+         */
+        public long sharedUboInitialSizeInBytes = 256 * 64;
     }
 
     private Engine(long nativeEngine, Config config) {
@@ -1529,7 +1540,8 @@ public class Engine {
             boolean disableHandleUseAfterFreeCheck,
             int preferredShaderLanguage,
             boolean forceGLES2Context, boolean assertNativeWindowIsValid,
-            int gpuContextPriority);
+            int gpuContextPriority,
+            long sharedUboInitialSizeInBytes);
     private static native void nSetBuilderFeatureLevel(long nativeBuilder, int ordinal);
     private static native void nSetBuilderSharedContext(long nativeBuilder, long sharedContext);
     private static native void nSetBuilderPaused(long nativeBuilder, boolean paused);

filament/include/filament/Engine.h

@@ -417,6 +417,17 @@ public:
          * GPU context priority level. Controls GPU work scheduling and preemption.
          */
         GpuContextPriority gpuContextPriority = GpuContextPriority::DEFAULT;
+
+        /**
+         * The initial size in bytes of the shared uniform buffer used for material instance
+         * batching.
+         *
+         * If the buffer runs out of space during a frame, it will be automatically reallocated
+         * with a larger capacity. Setting an appropriate initial size can help avoid runtime
+         * reallocations, which can cause a minor performance stutter, at the cost of higher
+         * initial memory usage.
+         */
+        uint32_t sharedUboInitialSizeInBytes = 256 * 64;
     };