Merge renderer+offscreen mode into unified graphics mode.

Allow Studio app to switch between graphics modes dynamically.

PiperOrigin-RevId: 878396966
Change-Id: I666fe3d2452de5404b9be2bd1d017eabec789aef

src/experimental/platform/CMakeLists.txt

@@ -41,6 +41,8 @@ target_sources(${MUJOCO_PLATFORM_TARGET_NAME}
         egl_utils.h
         enum_utils.h
         file_dialog.h
+        graphics_mode.cc
+        graphics_mode.h
         gui.cc
         gui.h
         gui_spec.cc
@@ -59,7 +61,6 @@ target_sources(${MUJOCO_PLATFORM_TARGET_NAME}
         plugin.h
         renderer.cc
         renderer.h
-        renderer_backend.h
         sim_history.cc
         sim_history.h
         sim_profiler.cc

src/experimental/platform/graphics_mode.cc

@@ -0,0 +1,51 @@
+// 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/platform/graphics_mode.h"
+
+namespace mujoco::platform {
+
+bool IsClassic(GraphicsMode gfx_mode) {
+  return gfx_mode == GraphicsMode::ClassicOpenGl ||
+         gfx_mode == GraphicsMode::ClassicOpenGlHeadless;
+}
+
+bool IsFilament(GraphicsMode gfx_mode) {
+  return gfx_mode == GraphicsMode::FilamentOpenGl ||
+         gfx_mode == GraphicsMode::FilamentVulkan ||
+         gfx_mode == GraphicsMode::FilamentWebGl ||
+         gfx_mode == GraphicsMode::FilamentOpenGlHeadless;
+}
+
+bool IsOpenGl(GraphicsMode gfx_mode) {
+  return gfx_mode == GraphicsMode::ClassicOpenGl ||
+         gfx_mode == GraphicsMode::ClassicOpenGlHeadless ||
+         gfx_mode == GraphicsMode::FilamentOpenGl ||
+         gfx_mode == GraphicsMode::FilamentOpenGlHeadless;
+}
+
+bool IsVulkan(GraphicsMode gfx_mode) {
+  return gfx_mode == GraphicsMode::FilamentVulkan;
+}
+
+bool IsWebGl(GraphicsMode gfx_mode) {
+  return gfx_mode == GraphicsMode::FilamentWebGl;
+}
+
+bool IsHeadless(GraphicsMode gfx_mode) {
+  return gfx_mode == GraphicsMode::ClassicOpenGlHeadless ||
+         gfx_mode == GraphicsMode::FilamentOpenGlHeadless;
+}
+
+}  // namespace mujoco::platform

src/experimental/platform/graphics_mode.h

@@ -12,23 +12,19 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-#ifndef MUJOCO_SRC_EXPERIMENTAL_PLATFORM_RENDERER_BACKEND_H_
-#define MUJOCO_SRC_EXPERIMENTAL_PLATFORM_RENDERER_BACKEND_H_
+#ifndef MUJOCO_SRC_EXPERIMENTAL_PLATFORM_GRAPHICS_MODE_H_
+#define MUJOCO_SRC_EXPERIMENTAL_PLATFORM_GRAPHICS_MODE_H_
 
 namespace mujoco::platform {
 
-// Describes the configuration of the renderer backend.
-//
-// This is generally a combination of two things. The first describes the
-// high-level rendering engine that sits behind the MuJoCo API (e.g.
-// mjr_render). The second describes the low-level graphics engine that is
-// powering the rendering (e.g. OpenGL, Vulkan, etc.).
-//
-// More details about the backends can be found in renderer.h.
-enum class RendererBackend {
+// Describes the configuration of the graphics and rendering systems.
+enum class GraphicsMode {
   // The classic MuJoCo OpenGL renderer.
   ClassicOpenGl,
 
+  // The classic MuJoCo OpenGL renderer.
+  ClassicOpenGlHeadless,
+
   // The Filament-based renderer running on OpenGL.
   FilamentOpenGl,
 
@@ -42,6 +38,13 @@ enum class RendererBackend {
   FilamentOpenGlHeadless,
 };
 
+bool IsClassic(GraphicsMode gfx_mode);
+bool IsFilament(GraphicsMode gfx_mode);
+bool IsOpenGl(GraphicsMode gfx_mode);
+bool IsVulkan(GraphicsMode gfx_mode);
+bool IsWebGl(GraphicsMode gfx_mode);
+bool IsHeadless(GraphicsMode gfx_mode);
+
 }  // namespace mujoco::platform
 
-#endif  // MUJOCO_SRC_EXPERIMENTAL_PLATFORM_RENDERER_BACKEND_H_
+#endif  // MUJOCO_SRC_EXPERIMENTAL_PLATFORM_GRAPHICS_MODE_H_

src/experimental/platform/renderer.cc

@@ -14,35 +14,41 @@
 
 #include "experimental/platform/renderer.h"
 
+#include <chrono>
 #include <cstddef>
 #include <span>
 
 #include <mujoco/mujoco.h>
-#include "experimental/platform/renderer_backend.h"
 
-#if defined(MUJOCO_RENDERER_CLASSIC_OPENGL)
 #include <imgui.h>
 #include <backends/imgui_impl_opengl3.h>
+#ifndef __EMSCRIPTEN__
 #include "experimental/platform/egl_utils.h"
-#else
+#endif  // __EMSCRIPTEN__
 #include "experimental/filament/render_context_filament.h"
+#include "experimental/platform/graphics_mode.h"
 #include "experimental/platform/plugin.h"
-#endif
 
 namespace mujoco::platform {
 
-Renderer::Renderer(void* native_window) : native_window_(native_window) {
-#ifdef MUJOCO_RENDERER_CLASSIC_OPENGL
-  if (native_window == nullptr) {
-    graphics_api_context_ = CreateEglContext();
+Renderer::Renderer(void* native_window, GraphicsMode gfx)
+    : native_window_(native_window), gfx_(gfx) {
+  if (IsClassic(gfx_)) {
+    if (native_window == nullptr) {
+      // graphics_api_context_ = CreateEglContext();
+    }
+    if (ImGui::GetCurrentContext()) {
+      ImGui_ImplOpenGL3_Init();
+    }
   }
-  if (ImGui::GetCurrentContext()) {
-    ImGui_ImplOpenGL3_Init();
-  }
-#endif
 }
 
 Renderer::~Renderer() {
+  if (IsClassic(gfx_)) {
+    if (ImGui::GetCurrentContext()) {
+      ImGui_ImplOpenGL3_Shutdown();
+    }
+  }
   Deinit();
   graphics_api_context_.reset();
 }
@@ -50,24 +56,39 @@ Renderer::~Renderer() {
 void Renderer::Init(const mjModel* model) {
   Deinit();
   if (model) {
-    mjr_defaultContext(&render_context_);
-
-#if defined(MUJOCO_RENDERER_CLASSIC_OPENGL)
-    mjr_makeContext(model, &render_context_, mjFONTSCALE_150);
-#else
-    mjrFilamentConfig render_config;
-    mjrf_defaultFilamentConfig(&render_config);
-    render_config.native_window = native_window_;
-    render_config.enable_gui = true;
-#if defined(MUJOCO_RENDERER_FILAMENT_OPENGL)
-    render_config.graphics_api = mjGFX_OPENGL;
-#elif defined(MUJOCO_RENDERER_FILAMENT_OPENGL_HEADLESS)
-    render_config.graphics_api = mjGFX_OPENGL;
-#elif defined(MUJOCO_RENDERER_FILAMENT_VULKAN)
-    render_config.graphics_api = mjGFX_VULKAN;
-#endif
-    mjrf_makeFilamentContext(model, &render_context_, &render_config);
-#endif
+    if (IsClassic(gfx_)) {
+      mjr_defaultContext(&render_context_);
+      mjr_makeContext(model, &render_context_, mjFONTSCALE_150);
+      render_ = [&](mjrRect rect, mjvScene* scene) {
+        mjr_render(rect, scene, &render_context_);
+      };
+      set_buffer_ = [&](int framebuffer) {
+        mjr_setBuffer(framebuffer, &render_context_);
+      };
+      read_pixels_ = [&](unsigned char* pixels, mjrRect rect) {
+        mjr_readPixels(pixels, nullptr, rect, &render_context_);
+        mjr_setBuffer(mjFB_WINDOW, &render_context_);
+      };
+    } else {
+      mjrf_defaultContext(&render_context_);
+      mjrFilamentConfig render_config;
+      mjrf_defaultFilamentConfig(&render_config);
+      render_config.native_window = native_window_;
+      render_config.enable_gui = true;
+      render_config.graphics_api =
+          IsOpenGl(gfx_) || IsWebGl(gfx_) ? mjGFX_OPENGL : mjGFX_VULKAN;
+      mjrf_makeFilamentContext(model, &render_context_, &render_config);
+      render_ = [&](mjrRect rect, mjvScene* scene) {
+        mjrf_render(rect, scene, &render_context_);
+      };
+      set_buffer_ = [&](int framebuffer) {
+        mjrf_setBuffer(framebuffer, &render_context_);
+      };
+      read_pixels_ = [&](unsigned char* pixels, mjrRect rect) {
+        mjrf_readPixels(pixels, nullptr, rect, &render_context_);
+        mjrf_setBuffer(mjFB_WINDOW, &render_context_);
+      };
+    }
 
     mjv_defaultScene(&scene_);
     mjv_makeScene(model, &scene_, 2000);
@@ -78,7 +99,11 @@ void Renderer::Init(const mjModel* model) {
 void Renderer::Deinit() {
   if (initialized_) {
     mjv_freeScene(&scene_);
-    mjr_freeContext(&render_context_);
+    if (IsClassic(gfx_)) {
+      mjr_freeContext(&render_context_);
+    } else {
+      mjrf_freeContext(&render_context_);
+    }
     initialized_ = false;
   }
 }
@@ -116,35 +141,30 @@ void Renderer::Render(const mjModel* model, mjData* data,
       mju_error("Offscreen mode requires a pixel buffer of size %d.",
                 width * height * 3);
     }
-
-    #ifdef MUJOCO_RENDERER_CLASSIC_OPENGL
+    if (IsClassic(gfx_)) {
       mjr_resizeOffscreen(width, height, &render_context_);
-      mjr_setBuffer(mjFB_OFFSCREEN, &render_context_);
-    #else
-      // The filament backend supports two offscreen framebuffers.
-      // mjFB_OFFSCREEN renders just the mjvScene data. +1 also includes the
-      // ImGui draw data.
-      mjr_setBuffer(mjFB_OFFSCREEN + 1, &render_context_);
-    #endif
+    }
+
+    // The filament backend supports two offscreen framebuffers.
+    // mjFB_OFFSCREEN renders just the mjvScene data. +1 also includes the
+    // ImGui draw data.
+    set_buffer_(IsClassic(gfx_) ? mjFB_OFFSCREEN : mjFB_OFFSCREEN + 1);
   }
 
   const mjrRect viewport = {0, 0, width, height};
-  mjr_render(viewport, &scene_, &render_context_);
+  render_(viewport, &scene_);
 
   // The filament backend knows how to renders the ImGui draw data. For the
   // classic backend, we need to render the ImGui draw data ourselves.
-  #ifdef MUJOCO_RENDERER_CLASSIC_OPENGL
-    if (ImGui::GetCurrentContext()) {
-      ImGui_ImplOpenGL3_NewFrame();
-      ImGui::Render();
-      ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
-    }
-  #endif
+  if (IsClassic(gfx_) && ImGui::GetCurrentContext()) {
+    ImGui_ImplOpenGL3_NewFrame();
+    ImGui::Render();
+    ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
+  }
 
   if (render_to_texture) {
     unsigned char* ptr = reinterpret_cast<unsigned char*>(pixels.data());
-    mjr_readPixels(ptr, nullptr, viewport, &render_context_);
-    mjr_setBuffer(mjFB_WINDOW, &render_context_);
+    read_pixels_(ptr, viewport);
   }
 
   UpdateFps();
@@ -158,61 +178,44 @@ void Renderer::RenderToTexture(const mjModel* model, mjData* data,
   }
 
   const mjrRect viewport = {0, 0, width, height};
-
-  mjr_setBuffer(mjFB_OFFSCREEN, &render_context_);
   mjv_updateCamera(model, data, camera, &scene_);
-  mjr_render(viewport, &scene_, &render_context_);
-  mjr_readPixels((unsigned char*)output, nullptr, viewport, &render_context_);
-  mjr_setBuffer(mjFB_WINDOW, &render_context_);
+
+  set_buffer_(mjFB_OFFSCREEN);
+  render_(viewport, &scene_);
+  read_pixels_((unsigned char*)output, viewport);
 }
 
 int Renderer::UploadImage(int texture_id, const std::byte* pixels, int width,
                           int height, int bpp) {
-#if defined(MUJOCO_RENDERER_CLASSIC_OPENGL)
-  return 0;
-#else
-  return mjrf_uploadGuiImage(texture_id,
-                             reinterpret_cast<const unsigned char*>(pixels),
-                             width, height, bpp, &render_context_);
-#endif
+  if (IsClassic(gfx_)) {
+    return 0;
+  } else {
+    return mjrf_uploadGuiImage(texture_id,
+                              reinterpret_cast<const unsigned char*>(pixels),
+                              width, height, bpp, &render_context_);
+  }
 }
 
 double Renderer::GetFps() { return fps_; }
 
 void Renderer::UpdateFps() {
-#ifdef MUJOCO_RENDERER_CLASSIC_OPENGL
-  TimePoint now = std::chrono::steady_clock::now();
-  TimePoint::duration delta_time = now - last_fps_update_;
-  const double interval = std::chrono::duration<double>(delta_time).count();
-  ++frames_;
-  if (interval > 0.2) {  // only update FPS stat at most 5 times per second
-    last_fps_update_ = now;
-    fps_ = frames_ / interval;
-    frames_ = 0;
+  if (IsClassic(gfx_)) {
+    TimePoint now = std::chrono::steady_clock::now();
+    TimePoint::duration delta_time = now - last_fps_update_;
+    const double interval = std::chrono::duration<double>(delta_time).count();
+    ++frames_;
+    if (interval > 0.2) {  // only update FPS stat at most 5 times per second
+      last_fps_update_ = now;
+      fps_ = frames_ / interval;
+      frames_ = 0;
+    }
+  } else {
+    fps_ = mjrf_getFrameRate(&render_context_);
   }
-#else
-  fps_ = mjrf_getFrameRate(&render_context_);
-#endif
 }
 
-RendererBackend Renderer::GetBackend() {
-#if defined(MUJOCO_RENDERER_FILAMENT_OPENGL_HEADLESS)
-  return RendererBackend::FilamentOpenGlHeadless;
-#elif defined(MUJOCO_RENDERER_FILAMENT_OPENGL)
-  return RendererBackend::FilamentOpenGl;
-#elif defined(MUJOCO_RENDERER_FILAMENT_VULKAN)
-  return RendererBackend::FilamentVulkan;
-#elif defined(MUJOCO_RENDERER_FILAMENT_WEBGL)
-  return RendererBackend::FilamentWebGl;
-#elif defined(MUJOCO_RENDERER_CLASSIC_OPENGL)
-  return RendererBackend::ClassicOpenGl;
-#else
-  #error "Unsupported renderer backend."
-#endif
-}
 }  // namespace mujoco::platform
 
-#if !defined(MUJOCO_RENDERER_CLASSIC_OPENGL)
 mjPLUGIN_LIB_INIT {
   mujoco::platform::GuiPlugin plugin;
   plugin.name = "Filament";
@@ -221,4 +224,3 @@ mjPLUGIN_LIB_INIT {
   };
   mujoco::platform::RegisterPlugin(plugin);
 }
-#endif

src/experimental/platform/renderer.h

@@ -17,13 +17,13 @@
 
 #include <chrono>
 #include <cstddef>
+#include <functional>
 #include <memory>
 #include <ratio>
 #include <span>
 
 #include <mujoco/mujoco.h>
-#include "experimental/platform/renderer_backend.h"
-
+#include "experimental/platform/graphics_mode.h"
 
 namespace mujoco::platform {
 
@@ -57,7 +57,8 @@ class Renderer {
   using Seconds = std::chrono::duration<double>;
   using Milliseconds = std::chrono::duration<double, std::milli>;
 
-  explicit Renderer(void* native_window = nullptr);
+  explicit Renderer(void* native_window = nullptr,
+                    GraphicsMode gfx_mode = GraphicsMode::FilamentVulkan);
   ~Renderer();
 
   Renderer(const Renderer&) = delete;
@@ -90,10 +91,6 @@ class Renderer {
   // Returns the current frame rate.
   double GetFps();
 
-  // Returns the statically-defined backend for which this renderer is
-  // configured.
-  static RendererBackend GetBackend();
-
  private:
   // Resets the renderer; no rendering will occur until Init() is called again.
   void Deinit();
@@ -101,7 +98,11 @@ class Renderer {
   void UpdateFps();
 
   void* native_window_ = nullptr;
+  GraphicsMode gfx_ = GraphicsMode::FilamentVulkan;
   std::shared_ptr<void> graphics_api_context_ = nullptr;
+  std::function<void(mjrRect, mjvScene*)> render_;
+  std::function<void(int)> set_buffer_;
+  std::function<void(unsigned char*, mjrRect)> read_pixels_;
   mjrContext render_context_;
   mjvScene scene_;
   bool initialized_ = false;

src/experimental/platform/window.cc

@@ -32,9 +32,10 @@
 #include <backends/imgui_impl_sdl2.h>
 #include <imgui.h>
 #include <mujoco/mujoco.h>
-#include "experimental/platform/renderer_backend.h"
+#include "experimental/platform/graphics_mode.h"
 #include "user/user_resource.h"
 
+
 // Because X11/Xlib.h defines Status.
 #ifdef Status
 #undef Status
@@ -95,12 +96,7 @@ static void InitImGui(SDL_Window* window, float content_scale, bool load_fonts,
 
 Window::Window(std::string_view title, int width, int height, Config config)
     : width_(width), height_(height), config_(config) {
-  const RendererBackend renderer_backend = config_.renderer_backend;
-  if (renderer_backend == RendererBackend::FilamentOpenGlHeadless) {
-    config_.offscreen_mode = true;
-  }
-
-  if (config_.offscreen_mode) {
+  if (IsHeadless(config_.gfx_mode)) {
     SDL_SetHint(SDL_HINT_RENDER_DRIVER, "software");
     SDL_SetHint(SDL_HINT_FRAMEBUFFER_ACCELERATION, "0");
   } else {
@@ -114,21 +110,19 @@ Window::Window(std::string_view title, int width, int height, Config config)
   }
 
   int window_flags = SDL_WINDOW_RESIZABLE | SDL_WINDOW_ALLOW_HIGHDPI;
-  if (renderer_backend == RendererBackend::FilamentVulkan) {
+  if (IsVulkan(config_.gfx_mode)) {
     window_flags |= SDL_WINDOW_VULKAN;
-  } else if (renderer_backend == RendererBackend::FilamentWebGl) {
+  } else if (IsWebGl(config_.gfx_mode)) {
     window_flags |= SDL_WINDOW_OPENGL;
     SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
     SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 0);
     SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_ES);
-  } else if (renderer_backend == RendererBackend::ClassicOpenGl ||
-             renderer_backend == RendererBackend::FilamentOpenGl ||
-             renderer_backend == RendererBackend::FilamentOpenGlHeadless) {
+  } else if (IsOpenGl(config_.gfx_mode)) {
     window_flags |= SDL_WINDOW_OPENGL;
     SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
     SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 0);
   } else {
-    mju_error("Unsupported window config: %d", renderer_backend);
+    mju_error("Unsupported window config: %d", config_.gfx_mode);
   }
 
   const float content_scale = ImGui_ImplSDL2_GetContentScaleForDisplay(0);
@@ -140,24 +134,29 @@ Window::Window(std::string_view title, int width, int height, Config config)
   }
 
   InitImGui(sdl_window_, content_scale, config.load_fonts,
-            (renderer_backend != RendererBackend::ClassicOpenGl));
+            (config_.gfx_mode != GraphicsMode::ClassicOpenGl &&
+             config_.gfx_mode != GraphicsMode::ClassicOpenGlHeadless));
 
-  if (renderer_backend == RendererBackend::FilamentWebGl ||
-      (renderer_backend == RendererBackend::ClassicOpenGl &&
-       !config.offscreen_mode)) {
+  // Filament (except WebGL) manages its own swap chain including when to swap.
+  // In all other cases, we'll use SDL to manage the swap chain.
+  if (config_.gfx_mode == GraphicsMode::FilamentWebGl ||
+      config_.gfx_mode == GraphicsMode::ClassicOpenGl ||
+      config_.gfx_mode == GraphicsMode::ClassicOpenGlHeadless) {
     SDL_GLContext gl_context = SDL_GL_CreateContext(sdl_window_);
     SDL_GL_MakeCurrent(sdl_window_, gl_context);
   }
 
-  if (config_.offscreen_mode) {
+  // In headless mode, we'll render to a texture and then blit the texture onto
+  // the window surface. In this case, we'll use SDL's software renderer to
+  // perform the blitting. Since we're in charge of the window, we don't need
+  // to get the native window handle for the renderer.
+  if (IsHeadless(config_.gfx_mode)) {
     sdl_renderer_ = SDL_CreateRenderer(sdl_window_, -1, SDL_RENDERER_SOFTWARE);
-  }
+  } else {
+    SDL_SysWMinfo wmi;
+    SDL_VERSION(&wmi.version);
+    SDL_GetWindowWMInfo(sdl_window_, &wmi);
 
-  SDL_SysWMinfo wmi;
-  SDL_VERSION(&wmi.version);
-  SDL_GetWindowWMInfo(sdl_window_, &wmi);
-
-  if (!config_.offscreen_mode) {
     #if defined(__linux__)
       native_window_ = reinterpret_cast<void*>(wmi.info.x11.window);
     #elif defined(__WIN32__)
@@ -175,6 +174,7 @@ Window::Window(std::string_view title, int width, int height, Config config)
 }
 
 Window::~Window() {
+  ImGui_ImplSDL2_Shutdown();
   SDL_DestroyWindow(sdl_window_);
   SDL_Quit();
 }
@@ -234,7 +234,9 @@ void Window::EndFrame() {
 }
 
 void Window::Present(std::span<const std::byte> pixels) {
-  if (config_.offscreen_mode) {
+  // In headless mode, we assume the caller has renderered the scene to an RGB
+  // buffer of size width_ * height_ * 3.
+  if (IsHeadless(config_.gfx_mode)) {
     if (pixels.size() != width_ * height_ * 3) {
       mju_error("Offscreen mode expects RGB buffer of size %d",
                 width_ * height_ * 3);
@@ -258,7 +260,9 @@ void Window::Present(std::span<const std::byte> pixels) {
       }
     }
 
-    if (config_.renderer_backend == RendererBackend::ClassicOpenGl) {
+    // Flip the image vertically because the classic renderer uses a bottom-left
+    // coordinate system while SDL assumes a top-left coordinate system.
+    if (config_.gfx_mode == GraphicsMode::ClassicOpenGlHeadless) {
       dst = static_cast<unsigned char*>(surface->pixels);
       for (int r = 0; r < height_ / 2; ++r) {
         unsigned char* top_row = &dst[4 * width_ * r];
@@ -268,13 +272,14 @@ void Window::Present(std::span<const std::byte> pixels) {
     }
 
     SDL_RenderPresent(sdl_renderer_);
-  } else if (config_.renderer_backend != RendererBackend::FilamentVulkan
-     && config_.renderer_backend != RendererBackend::FilamentOpenGl) {
+  } else if (config_.gfx_mode != GraphicsMode::FilamentVulkan
+     && config_.gfx_mode != GraphicsMode::FilamentOpenGl) {
     SDL_GL_SwapWindow(sdl_window_);
   }
 }
 
-bool Window::IsOffscreenMode() const {
-  return config_.offscreen_mode;
+GraphicsMode Window::GetGraphicsMode() const {
+  return config_.gfx_mode;
 }
+
 }  // namespace mujoco::platform

src/experimental/platform/window.h

@@ -20,10 +20,9 @@
 #include <string>
 #include <string_view>
 
-#include "experimental/platform/renderer_backend.h"
-
 #include <SDL_video.h>
 #include <SDL_render.h>
+#include "experimental/platform/graphics_mode.h"
 
 namespace mujoco::platform {
 
@@ -34,9 +33,8 @@ namespace mujoco::platform {
 class Window {
  public:
   struct Config {
-    RendererBackend renderer_backend = RendererBackend::ClassicOpenGl;
+    GraphicsMode gfx_mode = GraphicsMode::FilamentVulkan;
     bool load_fonts = true;
-    bool offscreen_mode = false;
   };
 
   Window(std::string_view title, int width, int height, Config config);
@@ -78,8 +76,8 @@ class Window {
   // the value will be cleared until the next time a file is dropped.
   std::string GetDropFile();
 
-  // Returns true if the window is in offscreen mode.
-  bool IsOffscreenMode() const;
+  // Returns the graphics configuration of the window.
+  GraphicsMode GetGraphicsMode() const;
 
   // Enables window resizing.
   void EnableWindowResizing();

src/experimental/studio/app.cc

@@ -25,6 +25,7 @@
 #include <filesystem>
 #include <functional>
 #include <memory>
+#include <optional>
 #include <span>
 #include <string>
 #include <string_view>
@@ -35,6 +36,7 @@
 #include <implot.h>
 #include <mujoco/mujoco.h>
 #include "experimental/platform/file_dialog.h"
+#include "experimental/platform/graphics_mode.h"
 #include "experimental/platform/gui.h"
 #include "experimental/platform/gui_spec.h"
 #include "experimental/platform/helpers.h"
@@ -111,14 +113,9 @@ static constexpr std::array<const char*, 31> kPercentRealTime = {
 };
 // clang-format on
 
-App::App(Config config) : ini_path_(std::move(config.ini_path)) {
-  platform::Window::Config window_config;
-  window_config.renderer_backend = platform::Renderer::GetBackend();
-  window_config.offscreen_mode = config.offscreen_mode;
-  window_ = std::make_unique<platform::Window>("MuJoCo Studio", config.width,
-                                               config.height, window_config);
-  renderer_ =
-      std::make_unique<platform::Renderer>(window_->GetNativeWindowHandle());
+App::App(Config config)
+    : ini_path_(std::move(config.ini_path)), gfx_mode_(config.gfx_mode) {
+  SwitchGraphicsMode(config.width, config.height, config.gfx_mode);
 
   ImPlot::CreateContext();
   mjv_defaultPerturb(&perturb_);
@@ -128,6 +125,20 @@ App::App(Config config) : ini_path_(std::move(config.ini_path)) {
   profiler_.Clear();
 }
 
+void App::SwitchGraphicsMode(int width, int height,
+                             platform::GraphicsMode mode) {
+  renderer_.reset();
+  window_.reset();
+  gfx_mode_ = mode;
+
+  platform::Window::Config window_config;
+  window_config.gfx_mode = gfx_mode_;
+  window_ = std::make_unique<platform::Window>("MuJoCo Studio", width, height,
+                                               window_config);
+  renderer_ = std::make_unique<platform::Renderer>(
+      window_->GetNativeWindowHandle(), gfx_mode_);
+}
+
 void App::ClearModel() {
   model_holder_.reset();
   window_->SetTitle("MuJoCo Studio");
@@ -361,8 +372,7 @@ void App::Render() {
   const float width = window_->GetWidth();
   const float height = window_->GetHeight();
   const float scale = window_->GetScale();
-
-  if (window_->IsOffscreenMode()) {
+  if (IsHeadless(window_->GetGraphicsMode())) {
     pixels_.resize(width * height * 3);
   } else {
     pixels_.clear();
@@ -615,14 +625,14 @@ void App::HandleKeyboardEvents() {
     return;
   }
 
-  constexpr auto ImGuiMode_CtrlShift = ImGuiMod_Ctrl | ImGuiMod_Shift;
+  constexpr auto ImGuiMod_CtrlShift = ImGuiMod_Ctrl | ImGuiMod_Shift;
 
   bool is_freecam_wasd = ui_.camera_idx == platform::kFreeCameraIdx;
 
   // Menu shortcuts.
   if (ImGui_IsChordJustPressed(ImGuiKey_O | ImGuiMod_Ctrl)) {
     tmp_.file_dialog = UiTempState::FileDialog_Load;
-  } else if (ImGui_IsChordJustPressed(ImGuiKey_S | ImGuiMode_CtrlShift)) {
+  } else if (ImGui_IsChordJustPressed(ImGuiKey_S | ImGuiMod_CtrlShift)) {
     tmp_.file_dialog = UiTempState::FileDialog_SaveMjb;
   } else if (ImGui_IsChordJustPressed(ImGuiKey_S | ImGuiMod_Ctrl)) {
     tmp_.file_dialog = UiTempState::FileDialog_SaveXml;
@@ -1898,6 +1908,51 @@ void App::MainMenuGui() {
       if (ImGui::MenuItem("Picture-in-Picture")) {
         tmp_.picture_in_picture = !tmp_.picture_in_picture;
       }
+      ImGui::Separator();
+
+
+      if (ImGui::BeginMenu("Graphics Mode (Experimental)")) {
+        std::optional<platform::GraphicsMode> mode;
+        if (ImGui::MenuItem(
+                "Classic OpenGL", nullptr,
+                gfx_mode_ == platform::GraphicsMode::ClassicOpenGl)) {
+          mode = platform::GraphicsMode::ClassicOpenGl;
+        }
+        if (ImGui::MenuItem(
+                "Classic OpenGL Headless", nullptr,
+                gfx_mode_ == platform::GraphicsMode::ClassicOpenGlHeadless)) {
+          mode = platform::GraphicsMode::ClassicOpenGlHeadless;
+        }
+        if (ImGui::MenuItem(
+                "Filament OpenGL", nullptr,
+                gfx_mode_ == platform::GraphicsMode::FilamentOpenGl)) {
+          mode = platform::GraphicsMode::FilamentOpenGl;
+        }
+        if (ImGui::MenuItem(
+                "Filament OpenGL Headless", nullptr,
+                gfx_mode_ == platform::GraphicsMode::FilamentOpenGlHeadless)) {
+          mode = platform::GraphicsMode::FilamentOpenGlHeadless;
+        }
+        if (ImGui::MenuItem(
+                "Filament Vulkan", nullptr,
+                gfx_mode_ == platform::GraphicsMode::FilamentVulkan)) {
+          mode = platform::GraphicsMode::FilamentVulkan;
+        }
+        if (mode.has_value()) {
+          spec_op_ = [=, this]() {
+            const int width = window_->GetWidth();
+            const int height = window_->GetHeight();
+            SwitchGraphicsMode(width, height, *mode);
+            // TODO: figure out why ImGui doesn't work unless we do this twice.
+            if (IsClassic(*mode)) {
+              SwitchGraphicsMode(width, height, *mode);
+            }
+            renderer_->Init(model());
+          };
+        }
+        ImGui::EndMenu();
+      }
+
       ImGui::EndMenu();
     }
 

src/experimental/studio/app.h

@@ -26,6 +26,7 @@
 #include <vector>
 
 #include <mujoco/mujoco.h>
+#include "experimental/platform/graphics_mode.h"
 #include "experimental/platform/gui.h"
 #include "experimental/platform/gui_spec.h"
 #include "experimental/platform/interaction.h"
@@ -51,10 +52,8 @@ class App {
     // The path to the ini file containing the user settings.
     std::string ini_path;
 
-    // By default, we render directly to the window surface. However, in some
-    // cases, we may want to render to an (offscreen) texture and blit the
-    // texture to the window surface.
-    bool offscreen_mode = false;
+    // The graphics configuration used for initializing the window.
+    platform::GraphicsMode gfx_mode = platform::GraphicsMode::FilamentVulkan;
   };
 
   explicit App(Config config);
@@ -190,6 +189,8 @@ class App {
   // then compile the spec to a model.
   void OnModelLoaded(std::string filename, ModelKind model_kind);
 
+  void SwitchGraphicsMode(int width, int height, platform::GraphicsMode mode);
+
   void SetLoadError(std::string error);
   void UpdateFilePaths(const std::string& resolved_path);
 
@@ -243,6 +244,7 @@ class App {
   std::optional<std::string> pending_load_;
   bool preserve_camera_on_load_ = false;
   ModelKind model_kind_ = kEmptyModel;
+  platform::GraphicsMode gfx_mode_ = platform::GraphicsMode::FilamentVulkan;
 
   std::unique_ptr<platform::Window> window_;
   std::unique_ptr<platform::Renderer> renderer_;

src/experimental/studio/main.cc

@@ -26,12 +26,13 @@
 
 #include <absl/flags/flag.h>
 #include <mujoco/mujoco.h>
+#include "experimental/platform/graphics_mode.h"
 #include "experimental/studio/app.h"
 
 ABSL_FLAG(int, window_width, 1400, "Window width");
 ABSL_FLAG(int, window_height, 720, "Window height");
 ABSL_FLAG(std::string, model_file, "", "MuJoCo model file.");
-ABSL_FLAG(bool, offscreen_mode, false, "Offscreen mode");
+ABSL_FLAG(std::string, gfx, "", "Graphics API");
 
 std::string Resolve(std::string_view path) {
   std::string_view subpath = path.substr(path.find(':') + 1);
@@ -99,14 +100,31 @@ int main(int argc, char** argv, char** envp) {
   resource_provider.prefix = "filament";
   mjp_registerResourceProvider(&resource_provider);
 
+  std::string gfx = absl::GetFlag(FLAGS_gfx);
+
+  mujoco::platform::GraphicsMode gfx_mode =
+      mujoco::platform::GraphicsMode::FilamentVulkan;
+  if (gfx == "classic") {
+    gfx_mode = mujoco::platform::GraphicsMode::ClassicOpenGl;
+  } else if (gfx == "classic_headless") {
+    gfx_mode = mujoco::platform::GraphicsMode::ClassicOpenGlHeadless;
+  } else if (gfx == "opengl") {
+    gfx_mode = mujoco::platform::GraphicsMode::FilamentOpenGl;
+  } else if (gfx == "opengl_headless") {
+    gfx_mode = mujoco::platform::GraphicsMode::FilamentOpenGlHeadless;
+  } else if (gfx == "vulkan" || gfx.empty()) {
+    gfx_mode = mujoco::platform::GraphicsMode::FilamentVulkan;
+  } else {
+    mju_error("Unsupported graphics API: %s", gfx.c_str());
+  }
+
   const int width = absl::GetFlag(FLAGS_window_width);
   const int height = absl::GetFlag(FLAGS_window_height);
-  const bool offscreen_mode = absl::GetFlag(FLAGS_offscreen_mode);
   mujoco::studio::App app({
     .width = width,
     .height = height,
     .ini_path = ini_path,
-    .offscreen_mode = offscreen_mode,
+    .gfx_mode = gfx_mode,
   });
 
   // If the model file is not specified, try to load it from the first argument

src/experimental/studio/wasm.cc

@@ -25,6 +25,7 @@
 #include <utility>
 
 #include <mujoco/mujoco.h>
+#include "experimental/platform/graphics_mode.h"
 #include "experimental/studio/app.h"
 
 // Global app instance. Lifetime is controlled by Init/Deinit calls which are
@@ -95,6 +96,7 @@ void Init() {
     .width = width,
     .height = height,
     .ini_path = ini_path,
+    .gfx_mode = mujoco::platform::GraphicsMode::FilamentWebGl,
   });
   g_app->InitEmptyModel();
 }