Fix various MuJoCo Studio build issues on Windows, MacOS and Linux

PiperOrigin-RevId: 833313973
Change-Id: I7ec181374e0bb49c32420d025044c31f6fc3c657

src/experimental/studio/CMakeLists.txt

@@ -47,6 +47,13 @@ target_compile_definitions(${MUJOCO_STUDIO_TARGET_NAME}
         -D${MUJOCO_STUDIO_RENDER_CONFIG}
 )
 
+if (WIN32)
+    target_compile_definitions(${MUJOCO_STUDIO_TARGET_NAME}
+        PRIVATE
+        -D_USE_MATH_DEFINES
+    )
+endif()
+
 include(third_party_deps/dear_imgui)
 include(third_party_deps/implot)
 target_link_libraries(${MUJOCO_STUDIO_TARGET_NAME}
@@ -63,13 +70,18 @@ target_link_libraries(${MUJOCO_STUDIO_TARGET_NAME}
 
 # Filament backend requires additional files to be copied into an "assets" folder.
 if(MUJOCO_USE_FILAMENT)
+    if(WIN32)
+        # Copy to work around lack of symlink permissions on Windows.
+        set(COPY_COMMAND copy_directory)
+    else()
+        set(COPY_COMMAND create_symlink)
+    endif()
     add_custom_command(
         TARGET ${MUJOCO_STUDIO_TARGET_NAME}
         POST_BUILD
-        COMMAND ${CMAKE_COMMAND}
-            -E create_symlink
-                ${CMAKE_RUNTIME_OUTPUT_DIRECTORY}/../src/experimental/filament/assets
-                ${CMAKE_RUNTIME_OUTPUT_DIRECTORY}/assets
+        COMMAND ${CMAKE_COMMAND} -E ${COPY_COMMAND}
+            ${CMAKE_RUNTIME_OUTPUT_DIRECTORY}/../src/experimental/filament/assets
+            ${CMAKE_RUNTIME_OUTPUT_DIRECTORY}/assets
         COMMENT "Copying Filament assets to build directory"
     )
 endif()

src/experimental/studio/app.cc

@@ -176,8 +176,8 @@ void App::OnModelLoaded(std::string_view model_file) {
     window_->SetTitle("MuJoCo Studio : " + std::string(model_file));
     tmp_.last_load_file = std::string(model_file_);
     std::filesystem::path path(model_file_);
-    base_path = std::string(path.parent_path()) + "/";
-    model_name = std::string(path.stem());
+    base_path = path.parent_path().string() + "/";
+    model_name = path.stem().string();
   } else {
     window_->SetTitle("MuJoCo Studio");
     tmp_.last_load_file = base_path;