CMake: add hdEmbree plugin detection and deployment

When the USD installation contains plugin/usd/hdEmbree/ (i.e. USD was built
with PXR_ENABLE_EMBREE_PLUGIN=ON), the build system now:
- Detects OPENUSD_HAS_EMBREE and logs status in the CMake configure output
- POST_BUILD: copies Embree runtime DLLs to the exe directory (looks in USD lib/
  first, or EMBREE_LOCATION cache variable if DLLs live in a separate SDK dir)
- install(): deploys hdEmbree.dll and Embree DLLs alongside other runtime DLLs
- Adds EMBREE_LOCATION CACHE PATH for pointing at an external Embree SDK bin/

No app code changes needed: UsdImagingGLEngine::GetRendererPlugins() already
enumerates all registered Hydra plugins, and the per-viewport renderer dropdown
already lists them. HdEmbree will appear automatically once the plugin is present.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

CMakeLists.txt

@@ -15,6 +15,26 @@ find_package(OpenUSD REQUIRED)
 find_package(Imgui REQUIRED)
 find_package(Glad REQUIRED)
 
+# User-supplied Embree SDK bin/ dir if Embree DLLs are not bundled inside USD lib/.
+set(EMBREE_LOCATION "" CACHE PATH "Embree SDK bin/ directory (leave empty if bundled in USD lib/)")
+
+# ── hdEmbree detection ───────────────────────────────────────────────────────
+set(HDEMBREE_PLUGIN_DIR "${OpenUSD_ROOT_DIR}/plugin/usd/hdEmbree")
+if(EXISTS "${HDEMBREE_PLUGIN_DIR}")
+    set(OPENUSD_HAS_EMBREE TRUE)
+    if(EMBREE_LOCATION AND EXISTS "${EMBREE_LOCATION}")
+        set(_embree_dll_dir "${EMBREE_LOCATION}")
+    else()
+        set(_embree_dll_dir "${OpenUSD_ROOT_DIR}/lib")
+    endif()
+    file(GLOB EMBREE_DLLS
+        "${_embree_dll_dir}/embree*.dll"
+        "${_embree_dll_dir}/tbb12.dll")
+else()
+    set(OPENUSD_HAS_EMBREE FALSE)
+    message(STATUS "hdEmbree: NOT found — rebuild USD with PXR_ENABLE_EMBREE_PLUGIN=ON to enable")
+endif()
+
 # Collect source files
 file(GLOB_RECURSE CORE_SOURCES "src/core/*.cpp")
 file(GLOB_RECURSE UI_SOURCES "src/ui/*.cpp")
@@ -78,6 +98,15 @@ if(WIN32)
             "$<TARGET_FILE_DIR:UsdLayerManager>"
         COMMENT "Copying runtime DLLs and USD plugins..."
     )
+
+    if(OPENUSD_HAS_EMBREE AND EMBREE_DLLS)
+        add_custom_command(TARGET UsdLayerManager POST_BUILD
+            COMMAND ${CMAKE_COMMAND} -E copy_if_different
+                ${EMBREE_DLLS}
+                "$<TARGET_FILE_DIR:UsdLayerManager>"
+            COMMENT "Copying Embree runtime DLLs..."
+        )
+    endif()
 endif()
 
 # Compiler warnings
@@ -118,6 +147,19 @@ install(FILES ${OpenUSD_ROOT_DIR}/plugin/usd/hdStorm.dll
     DESTINATION bin
 )
 
+if(OPENUSD_HAS_EMBREE)
+    install(FILES "${HDEMBREE_PLUGIN_DIR}/hdEmbree.dll"
+        DESTINATION bin
+        OPTIONAL
+    )
+    if(EMBREE_DLLS)
+        install(FILES ${EMBREE_DLLS}
+            DESTINATION bin
+            OPTIONAL
+        )
+    endif()
+endif()
+
 # Install Python runtime DLLs required by OpenUSD.
 install(FILES
     "$ENV{LOCALAPPDATA}/Programs/Python/Python312/python312.dll"
@@ -168,6 +210,12 @@ message(STATUS "ImGui found: ${Imgui_FOUND}")
 message(STATUS "OpenGL found: ${OPENGL_FOUND}")
 message(STATUS "Glad found: ${Glad_FOUND}")
 message(STATUS "Build tests: ${BUILD_TESTS}")
+message(STATUS "hdEmbree support: ${OPENUSD_HAS_EMBREE}")
+if(OPENUSD_HAS_EMBREE AND EMBREE_DLLS)
+    message(STATUS "Embree DLLs: ${EMBREE_DLLS}")
+elseif(OPENUSD_HAS_EMBREE)
+    message(WARNING "hdEmbree found but no Embree DLLs detected — set EMBREE_LOCATION to the Embree SDK bin/ dir")
+endif()
 message(STATUS "=======================================")
 message(STATUS "")