Add API function for querying frame stats.

Replaces the current GetFrameRate function.

PiperOrigin-RevId: 911897360
Change-Id: I4199ba9ce40d1d8bc37b551fa7058d964186641d

src/experimental/filament/compat/mjr_filament_renderer.cc

@@ -181,6 +181,13 @@ uintptr_t MjrFilamentRenderer::UploadGuiImage(uintptr_t tex_id,
   return imgui_bridge_->UploadImage(tex_id, pixels, width, height, bpp);
 }
 
+double MjrFilamentRenderer::GetFrameRate() const {
+  mjrFrameStats stats;
+  mjr_defaultFrameStats(&stats);
+  filament_context_->GetFrameStats(0, &stats);
+  return stats.frame_rate;
+}
+
 void MjrFilamentRenderer::UpdateGui() {
   mjrf_DEBUG_drawImguiEditor(scene_bridge_->GetScene());
 }

src/experimental/filament/compat/mjr_filament_renderer.h

@@ -65,9 +65,7 @@ class MjrFilamentRenderer {
   // Renders an ImGui window containing Filament-specific editor UI.
   void UpdateGui();
 
-  double GetFrameRate() const {
-    return filament_context_->GetFrameRate();
-  }
+  double GetFrameRate() const;
 
   MjrFilamentRenderer(const MjrFilamentRenderer&) = delete;
   MjrFilamentRenderer& operator=(const MjrFilamentRenderer&) = delete;

src/experimental/filament/filament/filament_context.cc

@@ -183,14 +183,16 @@ void FilamentContext::SetClearColor(const filament::math::float4& color) {
   renderer_->setClearOptions(opts);
 }
 
-double FilamentContext::GetFrameRate() const {
+void FilamentContext::GetFrameStats(mjrFrameHandle frame,
+                                    mjrFrameStats* stats_out) const {
   utils::FixedCapacityVector<filament::Renderer::FrameInfo> frame_info =
       renderer_->getFrameInfoHistory(1);
-  if (frame_info.empty()) {
-    return 0;
+  if (!frame_info.empty()) {
+    const int64_t ns = frame_info[0].denoisedGpuFrameDuration;
+    stats_out->frame_rate = 1.0e9 / static_cast<double>(ns);
+  } else {
+    stats_out->frame_rate = 0.0;
   }
-  const int64_t ns = frame_info[0].denoisedGpuFrameDuration;
-  return 1.0e9 / static_cast<double>(ns);
 }
 
 }  // namespace mujoco

src/experimental/filament/filament/filament_context.h

@@ -52,8 +52,8 @@ class FilamentContext : public mjrfContext {
   // Sets the clear color for the renderer.
   void SetClearColor(const filament::math::float4& color);
 
-  // Returns the current frame rate of the renderer.
-  double GetFrameRate() const;
+  // Returns information about the frame.
+  void GetFrameStats(mjrFrameHandle frame, mjrFrameStats* stats_out) const;
 
   filament::Engine* GetEngine() const { return engine_; }
 

src/experimental/filament/render_context_filament.cc

@@ -145,6 +145,10 @@ void mjr_defaultReadPixelsRequest(mjrReadPixelsRequest* request) {
   memset(request, 0, sizeof(mjrReadPixelsRequest));
 }
 
+void mjr_defaultFrameStats(mjrFrameStats* stats) {
+  memset(stats, 0, sizeof(mjrFrameStats));
+}
+
 mjrfContext* mjrf_createContext(const mjrFilamentConfig* config) {
   return new mujoco::FilamentContext(config);
 }
@@ -355,6 +359,11 @@ void mjrf_waitForFrame(mjrfContext* ctx, mjrFrameHandle frame) {
   mujoco::FilamentContext::downcast(ctx)->WaitForFrame(frame);
 }
 
+void mjrf_getFrameStats(mjrfContext* ctx, mjrFrameHandle frame,
+                        mjrFrameStats* stats_out) {
+  mujoco::FilamentContext::downcast(ctx)->GetFrameStats(frame, stats_out);
+}
+
 // Legacy API, to be deprecated.
 
 void mjrf_makeFilamentContext(const mjModel* m, mjrContext* con,

src/experimental/filament/render_context_filament.h

@@ -406,6 +406,15 @@ struct mjrReadPixelsRequest {
 // Initializes the mjrReadPixelsRequest to default values.
 void mjr_defaultReadPixelsRequest(mjrReadPixelsRequest* request);
 
+// Information about a single frame of rendering.
+struct mjrFrameStats {
+  // The frame rate of the renderer, in frames per second.
+  double frame_rate;
+};
+
+// Initializes the mjrFrameStats to default values.
+void mjr_defaultFrameStats(mjrFrameStats* stats);
+
 // Configuration parameters for the filament rendering context.
 struct mjrFilamentConfig {
   // The native window handle into which we can render directly.
@@ -562,6 +571,10 @@ mjrFrameHandle mjrf_render(mjrfContext* ctx, const mjrRenderRequest* req,
 // Waits for the rendering to complete for the given frame handle.
 void mjrf_waitForFrame(mjrfContext* ctx, mjrFrameHandle frame);
 
+// Returns the stats for the given frame but updating the given `stats_out`.
+void mjrf_getFrameStats(mjrfContext* ctx, mjrFrameHandle frame,
+                        mjrFrameStats* stats_out);
+
 // Draws an ImGui editor for the given scene, exposing filament-specific
 // settings.
 void mjrf_DEBUG_drawImguiEditor(mjrScene* scene);