Adds function for creating the filament Platform based on the renderer

configuration.

PiperOrigin-RevId: 889226229
Change-Id: Ia5bcdc16e9861e39c49422c2d5fccee23e477af6

src/experimental/filament/CMakeLists.txt

@@ -33,6 +33,8 @@ target_sources(${MUJOCO_FILAMENT_TARGET_NAME}
         filament/drawable.h
         filament/filament_context.cc
         filament/filament_context.h
+        filament/filament_platform_factory.cc
+        filament/filament_platform_factory.h
         filament/geom_util.cc
         filament/geom_util.h
         filament/gui_view.cc

src/experimental/filament/filament/filament_context.cc

@@ -38,6 +38,7 @@
 #include <mujoco/mjmodel.h>
 #include <mujoco/mjvisualize.h>
 #include <mujoco/mujoco.h>
+#include "experimental/filament/filament/filament_platform_factory.h"
 #include "experimental/filament/filament/gui_view.h"
 #include "experimental/filament/filament/imgui_editor.h"
 #include "experimental/filament/filament/object_manager.h"
@@ -51,31 +52,20 @@ namespace mujoco {
 FilamentContext::FilamentContext(const mjrFilamentConfig* config,
                                  const mjModel* model, mjrContext* con)
     : config_(*config), context_(con), model_(model) {
-#if defined( __EMSCRIPTEN__)
+  FilamentPlatformSetup setup = CreateFilamentPlatform(config_);
-  filament::Engine::Backend backend = filament::Engine::Backend::OPENGL;
+  platform_ = std::move(setup.platform);
-#else
-  filament::Engine::Backend backend = filament::Engine::Backend::VULKAN;
-#endif
 
-  switch (config_.graphics_api) {
+  filament::Engine::Builder engine_builder;
-    case mjGFX_DEFAULT:
+  engine_builder.backend(setup.backend);
-      // Use the default based on the platform above.
+  engine_builder.platform(platform_.get());
-      break;
+  engine_builder.feature("backend.disable_parallel_shader_compile",
-    case mjGFX_OPENGL:
+                         setup.disable_parallel_shader_compile);
-      backend = filament::Engine::Backend::OPENGL;
+  engine_ = engine_builder.build();
-      break;
+
-    case mjGFX_VULKAN:
+  renderer_ = engine_->createRenderer();
-      backend = filament::Engine::Backend::VULKAN;
-      break;
-    default:
-      mju_error("Unsupported graphics API: %d", config_.graphics_api);
-  }
 
   const int width = model_->vis.global.offwidth;
   const int height = model_->vis.global.offheight;
-
-  engine_ = filament::Engine::create(backend);
-  renderer_ = engine_->createRenderer();
   #ifdef __EMSCRIPTEN__
     window_swap_chain_ = engine_->createSwapChain(nullptr);
   #else

src/experimental/filament/filament/filament_context.h

@@ -18,6 +18,7 @@
 #include <cstdint>
 #include <memory>
 
+#include <backend/Platform.h>
 #include <filament/Engine.h>
 #include <filament/Renderer.h>
 #include <mujoco/mjmodel.h>
@@ -73,10 +74,13 @@ class FilamentContext {
   mjrFilamentConfig config_;
   mjrContext* context_ = nullptr;
   const mjModel* model_ = nullptr;
+
   filament::Engine* engine_ = nullptr;
+  filament::Renderer* renderer_ = nullptr;
   filament::SwapChain* window_swap_chain_ = nullptr;
   filament::SwapChain* offscreen_swap_chain_ = nullptr;
-  filament::Renderer* renderer_ = nullptr;
+  std::unique_ptr<filament::backend::Platform> platform_;
+
   SceneView::DrawMode last_render_mode_ = SceneView::DrawMode::kNormal;
   SwapChainType scene_swap_chain_target_ = kWindowSwapChain;
   SwapChainType gui_swap_chain_target_ = kWindowSwapChain;

src/experimental/filament/filament/filament_platform_factory.cc

@@ -0,0 +1,78 @@
+// Copyright 2026 DeepMind Technologies Limited
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "experimental/filament/filament/filament_platform_factory.h"
+
+#include <memory>
+
+#include <backend/Platform.h>
+
+#ifdef __linux__
+#include <backend/platforms/PlatformEGL.h>
+#include <backend/platforms/PlatformEGLHeadless.h>  // IWYU pragma: keep
+#include <backend/platforms/PlatformGLX.h>
+#include <backend/platforms/VulkanPlatformLinux.h>
+#include "third_party/filament/libs/bluegl/include/bluegl/BlueGL.h"
+#endif
+
+#include <filament/Engine.h>
+#include <mujoco/mujoco.h>
+#include "experimental/filament/render_context_filament.h"
+
+namespace mujoco {
+
+static filament::Engine::Backend ResolveBackend(int graphics_api) {
+#if defined(__EMSCRIPTEN__)
+  filament::Engine::Backend backend = filament::Engine::Backend::OPENGL;
+#else
+  filament::Engine::Backend backend = filament::Engine::Backend::VULKAN;
+#endif
+
+  switch (graphics_api) {
+    case mjGFX_DEFAULT:
+      // Use the default based on the platform above.
+      break;
+    case mjGFX_OPENGL:
+      backend = filament::Engine::Backend::OPENGL;
+      break;
+    case mjGFX_VULKAN:
+      backend = filament::Engine::Backend::VULKAN;
+      break;
+    default:
+      mju_error("Unsupported graphics API: %d", graphics_api);
+  }
+  return backend;
+}
+
+FilamentPlatformSetup CreateFilamentPlatform(const mjrFilamentConfig& config) {
+  FilamentPlatformSetup setup;
+  setup.backend = ResolveBackend(config.graphics_api);
+
+#ifdef __linux__
+  if (setup.backend == filament::Engine::Backend::OPENGL) {
+    if (config.native_window == nullptr) {
+      setup.platform = std::make_unique<filament::backend::PlatformEGLHeadless>();
+      setup.disable_parallel_shader_compile = true;
+    } else {
+      setup.platform = std::make_unique<filament::backend::PlatformGLX>();
+    }
+  } else {
+    setup.platform = std::make_unique<filament::backend::VulkanPlatformLinux>();
+  }
+#endif
+  return setup;
+}
+
+
+}  // namespace mujoco

src/experimental/filament/filament/filament_platform_factory.h

@@ -0,0 +1,45 @@
+// Copyright 2026 DeepMind Technologies Limited
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef MUJOCO_SRC_EXPERIMENTAL_FILAMENT_FILAMENT_FILAMENT_PLATFORM_FACTORY_H_
+#define MUJOCO_SRC_EXPERIMENTAL_FILAMENT_FILAMENT_FILAMENT_PLATFORM_FACTORY_H_
+
+#include <memory>
+
+#include "experimental/filament/render_context_filament.h"
+#include <backend/Platform.h>
+#include <filament/Engine.h>
+
+namespace mujoco {
+
+struct FilamentPlatformSetup {
+  // The filament::Platform to use for the engine. May be null, in which case
+  // the engine will be created with a default platform.
+  std::unique_ptr<filament::backend::Platform> platform = nullptr;
+
+  // The filament::Engine::Backend to use for the engine.
+  filament::Engine::Backend backend;
+
+  // Whether to disable parallel shader compilation.
+  bool disable_parallel_shader_compile = false;
+};
+
+// Creates a filament::Platform based on the given config and defines the
+// filament::Engine::Backend to use. Also returns additional information for
+// setting up the filament::Engine for use with the provided Platform.
+FilamentPlatformSetup CreateFilamentPlatform(const mjrFilamentConfig& config);
+
+}  // namespace mujoco
+
+#endif  // MUJOCO_SRC_EXPERIMENTAL_FILAMENT_FILAMENT_FILAMENT_PLATFORM_FACTORY_H_