CMake: support separate HDEMBREE_USD_ROOT for hdEmbree integration

The previous approach assumed hdEmbree lived inside OpenUSD_ROOT_DIR, which
only works when USD itself was built with PXR_ENABLE_EMBREE_PLUGIN=ON.

This change adds HDEMBREE_USD_ROOT to point at a separate USD build that
includes hdEmbree (e.g. E:/USD_v25.05_embree), while the main USD install
remains at OpenUSD_ROOT_DIR. Fixes three bugs from the prior commit:

- Detection now resolves _hdembree_root from HDEMBREE_USD_ROOT first
- hdEmbree.dll path corrected: it lives at plugin/usd/hdEmbree.dll, not
  inside the plugin/usd/hdEmbree/ metadata subdirectory
- DLL glob changed from tbb12.dll (Embree 4) to embree*.dll only; tbb*.dll
  is deliberately excluded to avoid conflicts with the main USD install
- POST_BUILD now also deploys the hdEmbree/ metadata dir to usd/hdEmbree/
- install() deploys the hdEmbree/ metadata dir alongside hdEmbree.dll

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

CMakeLists.txt

@@ -15,24 +15,35 @@ 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/)")
+# USD build that includes hdEmbree (built with PXR_ENABLE_EMBREE_PLUGIN=ON).
+# Can be a separate install from OpenUSD_ROOT_DIR; leave empty to search there instead.
+set(HDEMBREE_USD_ROOT "" CACHE PATH "USD build containing hdEmbree plugin (separate from OpenUSD_ROOT_DIR)")
+# Only needed if embree*.dll are not inside HDEMBREE_USD_ROOT/bin.
+set(EMBREE_LOCATION "" CACHE PATH "Embree SDK bin/ directory (leave empty if bundled in HDEMBREE_USD_ROOT/bin)")
 
 # ── hdEmbree detection ───────────────────────────────────────────────────────
-set(HDEMBREE_PLUGIN_DIR "${OpenUSD_ROOT_DIR}/plugin/usd/hdEmbree")
+if(HDEMBREE_USD_ROOT AND EXISTS "${HDEMBREE_USD_ROOT}")
+    set(_hdembree_root "${HDEMBREE_USD_ROOT}")
+else()
+    set(_hdembree_root "${OpenUSD_ROOT_DIR}")
+endif()
+
+# hdEmbree.dll lives at plugin/usd/hdEmbree.dll; the subdir holds only plugin metadata.
+set(HDEMBREE_PLUGIN_DIR "${_hdembree_root}/plugin/usd/hdEmbree")
+set(HDEMBREE_DLL        "${_hdembree_root}/plugin/usd/hdEmbree.dll")
+
 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")
+        set(_embree_dll_dir "${_hdembree_root}/bin")
     endif()
-    file(GLOB EMBREE_DLLS
-        "${_embree_dll_dir}/embree*.dll"
-        "${_embree_dll_dir}/tbb12.dll")
+    # Skip tbb*.dll — already supplied by the main USD install to avoid conflicts.
+    file(GLOB EMBREE_DLLS "${_embree_dll_dir}/embree*.dll")
 else()
     set(OPENUSD_HAS_EMBREE FALSE)
-    message(STATUS "hdEmbree: NOT found — rebuild USD with PXR_ENABLE_EMBREE_PLUGIN=ON to enable")
+    message(STATUS "hdEmbree: NOT found — set HDEMBREE_USD_ROOT to a USD build with PXR_ENABLE_EMBREE_PLUGIN=ON")
 endif()
 
 # Collect source files
@@ -99,13 +110,24 @@ if(WIN32)
         COMMENT "Copying runtime DLLs and USD plugins..."
     )
 
-    if(OPENUSD_HAS_EMBREE AND EMBREE_DLLS)
+    if(OPENUSD_HAS_EMBREE)
         add_custom_command(TARGET UsdLayerManager POST_BUILD
             COMMAND ${CMAKE_COMMAND} -E copy_if_different
-                ${EMBREE_DLLS}
+                "${HDEMBREE_DLL}"
                 "$<TARGET_FILE_DIR:UsdLayerManager>"
-            COMMENT "Copying Embree runtime DLLs..."
+            COMMAND ${CMAKE_COMMAND} -E copy_directory
+                "${HDEMBREE_PLUGIN_DIR}"
+                "$<TARGET_FILE_DIR:UsdLayerManager>/usd/hdEmbree"
+            COMMENT "Copying hdEmbree plugin..."
         )
+        if(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()
 endif()
 
@@ -148,10 +170,14 @@ install(FILES ${OpenUSD_ROOT_DIR}/plugin/usd/hdStorm.dll
 )
 
 if(OPENUSD_HAS_EMBREE)
-    install(FILES "${HDEMBREE_PLUGIN_DIR}/hdEmbree.dll"
+    install(FILES "${HDEMBREE_DLL}"
         DESTINATION bin
         OPTIONAL
     )
+    install(DIRECTORY "${HDEMBREE_PLUGIN_DIR}"
+        DESTINATION bin/usd
+        OPTIONAL
+    )
     if(EMBREE_DLLS)
         install(FILES ${EMBREE_DLLS}
             DESTINATION bin
@@ -214,7 +240,7 @@ 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")
+    message(WARNING "hdEmbree found but no Embree DLLs detected — set EMBREE_LOCATION to the Embree SDK bin/ dir or check HDEMBREE_USD_ROOT/bin")
 endif()
 message(STATUS "=======================================")
 message(STATUS "")