CMake: add hdCycles Hydra delegate build and deployment

- Build Cycles from third_party/cycles via ExternalProject (WITH_CYCLES=ON)
- Deploy hdCycles.dll + plugin metadata to usd/ alongside hdEmbree/hdArnold
- Copy Cycles runtime deps (embree4, openvdb, OIDN, sycl, imath, etc.) via
  a cmake -P script that globs at build time, excluding CRT DLLs to avoid
  MSVCP140 version conflicts
- Deploy tbb12.dll explicitly from the precompiled lib tree (required by
  openvdb/embree4 but absent from the install output)
- Bake all renderer paths into CMakePresets.json default preset
  (WITH_CYCLES, HDARNOLD_ROOT -> E:/library/hdArnold, ARNOLD_LOCATION,
  HDEMBREE_USD_ROOT) so a fresh configure needs no manual -D flags

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

CMakeLists.txt

@@ -60,14 +60,96 @@ if(HDARNOLD_ROOT AND EXISTS "${HDARNOLD_ROOT}/plugin/hdArnold.dll")
     set(NDRARNOLD_PLUGIN_DIR  "${HDARNOLD_ROOT}/plugin/ndrArnold")
     if(ARNOLD_LOCATION AND EXISTS "${ARNOLD_LOCATION}/bin/ai.dll")
         set(ARNOLD_AI_DLL "${ARNOLD_LOCATION}/bin/ai.dll")
+        # ai.dll also requires companion runtime DLLs (OIDN denoiser, Adsk licensing, cer)
+        file(GLOB ARNOLD_RUNTIME_DLLS
+            "${ARNOLD_LOCATION}/bin/ai*.dll"
+            "${ARNOLD_LOCATION}/bin/AdClm*.dll"
+            "${ARNOLD_LOCATION}/bin/AdskLicensing*.dll"
+            "${ARNOLD_LOCATION}/bin/cer.dll"
+        )
     else()
         set(ARNOLD_AI_DLL "")
+        set(ARNOLD_RUNTIME_DLLS "")
     endif()
 else()
     set(OPENUSD_HAS_ARNOLD FALSE)
     message(STATUS "hdArnold: NOT found — set HDARNOLD_ROOT to the arnold-usd install dir and ARNOLD_LOCATION to the MtoA root")
 endif()
 
+# ── Cycles hdCycles Hydra render delegate ────────────────────────────────────
+# Build Blender Cycles from third_party/cycles using ExternalProject.
+# Set WITH_CYCLES=ON to enable; requires MSVC, and uses the precompiled libs
+# bundled in third_party/cycles/lib/windows_x64/.
+# hdCycles.dll is deployed to usd/ alongside hdEmbree and hdArnold.
+option(WITH_CYCLES "Build Cycles Hydra render delegate from third_party/cycles" OFF)
+
+set(CYCLES_BINARY_DIR  "${CMAKE_BINARY_DIR}/cycles_build")
+set(CYCLES_INSTALL_DIR "${CMAKE_BINARY_DIR}/cycles_install")
+set(HDCYCLES_DLL        "${CYCLES_INSTALL_DIR}/hydra/hdCycles.dll")
+set(HDCYCLES_PLUGIN_DIR "${CYCLES_INSTALL_DIR}/hydra/hdCycles")
+# tbb12.dll is required by openvdb/embree4 but lives in the precompiled lib tree,
+# not in the install output — deploy it explicitly.
+set(CYCLES_TBB12_DLL "${CMAKE_SOURCE_DIR}/third_party/cycles/lib/windows_x64/tbb/bin/tbb12.dll")
+
+if(WITH_CYCLES)
+    include(ExternalProject)
+
+    # Resolve absolute USD root so we can forward it to the sub-build.
+    # FindOpenUSD.cmake stores the path in OpenUSD_ROOT_DIR.
+    if(NOT OpenUSD_ROOT_DIR)
+        message(FATAL_ERROR "WITH_CYCLES requires OpenUSD_ROOT_DIR to be set (run find_package(OpenUSD) first).")
+    endif()
+
+    ExternalProject_Add(CyclesBuild
+        SOURCE_DIR "${CMAKE_SOURCE_DIR}/third_party/cycles"
+        BINARY_DIR "${CYCLES_BINARY_DIR}"
+        INSTALL_DIR "${CYCLES_INSTALL_DIR}"
+        CMAKE_ARGS
+            # Always Release — Cycles' Debug build is slow and rarely needed here.
+            -DCMAKE_BUILD_TYPE=Release
+            -DCMAKE_INSTALL_PREFIX=<INSTALL_DIR>
+            # Point Cycles at our app's USD so hdCycles is ABI-compatible.
+            -DPXR_ROOT=${OpenUSD_ROOT_DIR}
+            # Hydra delegate is the only deliverable we need.
+            -DWITH_CYCLES_HYDRA_RENDER_DELEGATE=ON
+            -DWITH_CYCLES_USD=ON
+            # Use bundled precompiled libs from lib/windows_x64/.
+            -DWITH_LIBS_PRECOMPILED=ON
+            # Turn off heavy optional features that aren't needed for the delegate.
+            -DWITH_CYCLES_STANDALONE_GUI=OFF
+            -DWITH_CYCLES_DEVICE_CUDA=OFF
+            -DWITH_CYCLES_DEVICE_OPTIX=OFF
+            -DWITH_CYCLES_DEVICE_HIP=OFF
+            -DWITH_CYCLES_DEVICE_ONEAPI=OFF
+            -DWITH_CYCLES_LOGGING=OFF
+            # ---- pxrConfig.cmake dependency overrides ----
+            # pxrConfig.cmake runs find_dependency() for these before Cycles'
+            # precompiled lib paths are on CMAKE_PREFIX_PATH, so we must supply
+            # them explicitly.  The Python3 vars also override the hardcoded
+            # CI build-machine path embedded in pxrConfig.cmake.
+            -DPython3_EXECUTABLE=$ENV{LOCALAPPDATA}/Programs/Python/Python312/python.exe
+            -DPython3_LIBRARY=$ENV{LOCALAPPDATA}/Programs/Python/Python312/libs/python312.lib
+            -DPython3_INCLUDE_DIR=$ENV{LOCALAPPDATA}/Programs/Python/Python312/include
+            -DTBB_DIR=${OpenUSD_ROOT_DIR}/lib/cmake/TBB
+            -DMaterialX_DIR=${OpenUSD_ROOT_DIR}/lib/cmake/MaterialX
+            # Our USD install has no standalone OpenSubdiv/Imath cmake packages
+            # (they're linked into the USD DLLs); skip those find_dependency calls.
+            -DPXR_FIND_OPENSUBDIV_IN_CONFIG=OFF
+            -DPXR_FIND_IMATH_IN_CONFIG=OFF
+        BUILD_COMMAND
+            ${CMAKE_COMMAND} --build <BINARY_DIR> --config Release
+        INSTALL_COMMAND
+            ${CMAKE_COMMAND} --install <BINARY_DIR> --config Release
+        BUILD_BYPRODUCTS
+            "${HDCYCLES_DLL}"
+    )
+
+    set(OPENUSD_HAS_CYCLES TRUE)
+else()
+    set(OPENUSD_HAS_CYCLES FALSE)
+    message(STATUS "hdCycles: disabled — set WITH_CYCLES=ON to build from third_party/cycles")
+endif()
+
 # Collect source files
 file(GLOB_RECURSE CORE_SOURCES "src/core/*.cpp")
 file(GLOB_RECURSE UI_SOURCES "src/ui/*.cpp")
@@ -97,6 +179,12 @@ target_link_libraries(UsdLayerManager PRIVATE
     Glad::Glad
 )
 
+# Cycles is an ExternalProject; UsdLayerManager must wait for it to finish
+# before POST_BUILD copies hdCycles.dll to the output directory.
+if(WITH_CYCLES)
+    add_dependencies(UsdLayerManager CyclesBuild)
+endif()
+
 # Platform-specific settings
 if(WIN32)
     # Windows-specific settings
@@ -171,15 +259,61 @@ if(WIN32)
                 "$<TARGET_FILE_DIR:UsdLayerManager>/usd/ndrArnold"
             COMMENT "Copying hdArnold plugin..."
         )
-        if(ARNOLD_AI_DLL)
+        if(ARNOLD_RUNTIME_DLLS)
             add_custom_command(TARGET UsdLayerManager POST_BUILD
                 COMMAND ${CMAKE_COMMAND} -E copy_if_different
-                    "${ARNOLD_AI_DLL}"
+                    ${ARNOLD_RUNTIME_DLLS}
                     "$<TARGET_FILE_DIR:UsdLayerManager>"
-                COMMENT "Copying Arnold runtime ai.dll..."
+                COMMENT "Copying Arnold runtime DLLs (ai, OIDN, licensing)..."
             )
         endif()
     endif()
+
+    if(OPENUSD_HAS_CYCLES)
+        # hdCycles uses the same usd/ layout as hdEmbree:
+        #   usd/hdCycles.dll  +  usd/hdCycles/resources/plugInfo.json
+        # The bundled plugInfo.json has Root=".." and LibraryPath="../hdCycles.dll"
+        # which resolves correctly once the plugin dir lives in usd/.
+        #
+        # Runtime deps (embree4, epoxy, imath, openvdb, OIDN, sycl, vulkan, etc.)
+        # live in CYCLES_INSTALL_DIR root and must be next to the exe.  We can't
+        # file(GLOB) them at configure time (ExternalProject hasn't run yet), so we
+        # write a small cmake -P script that globs them at build time instead.
+        # The script runs at build time (after ExternalProject finishes) so it can glob
+        # the actual install output.  CRT/Windows DLLs are excluded — they must come
+        # from the system or the main exe's toolchain, not from Cycles' bundled copy.
+        file(WRITE "${CMAKE_BINARY_DIR}/copy_cycles_runtime_dlls.cmake"
+            "file(GLOB _all_dlls \"${CYCLES_INSTALL_DIR}/*.dll\")\n"
+            "set(_dlls)\n"
+            "foreach(_dll \${_all_dlls})\n"
+            "    get_filename_component(_name \"\${_dll}\" NAME)\n"
+            "    string(TOLOWER \"\${_name}\" _lname)\n"
+            "    if(_lname MATCHES \"^(msvcp|vcruntime|ucrtbase|concrt|api-ms-win-)\")\n"
+            "        continue()\n"
+            "    endif()\n"
+            "    list(APPEND _dlls \"\${_dll}\")\n"
+            "endforeach()\n"
+            "if(_dlls)\n"
+            "    file(COPY \${_dlls} DESTINATION \"\${DEST_DIR}\")\n"
+            "endif()\n"
+        )
+        add_custom_command(TARGET UsdLayerManager POST_BUILD
+            COMMAND ${CMAKE_COMMAND} -E copy_if_different
+                "${HDCYCLES_DLL}"
+                "$<TARGET_FILE_DIR:UsdLayerManager>/usd/hdCycles.dll"
+            COMMAND ${CMAKE_COMMAND} -E copy_directory
+                "${HDCYCLES_PLUGIN_DIR}"
+                "$<TARGET_FILE_DIR:UsdLayerManager>/usd/hdCycles"
+            COMMAND ${CMAKE_COMMAND}
+                "-DDEST_DIR=$<TARGET_FILE_DIR:UsdLayerManager>"
+                -P "${CMAKE_BINARY_DIR}/copy_cycles_runtime_dlls.cmake"
+            # tbb12.dll is required by openvdb/embree4 but is not in the install output
+            COMMAND ${CMAKE_COMMAND} -E copy_if_different
+                "${CYCLES_TBB12_DLL}"
+                "$<TARGET_FILE_DIR:UsdLayerManager>/tbb12.dll"
+            COMMENT "Copying hdCycles plugin and runtime DLLs..."
+        )
+    endif()
 endif()
 
 # Compiler warnings
@@ -251,14 +385,36 @@ if(OPENUSD_HAS_ARNOLD)
         DESTINATION bin/usd
         OPTIONAL
     )
-    if(ARNOLD_AI_DLL)
+    if(ARNOLD_RUNTIME_DLLS)
-        install(FILES "${ARNOLD_AI_DLL}"
+        install(FILES ${ARNOLD_RUNTIME_DLLS}
             DESTINATION bin
             OPTIONAL
         )
     endif()
 endif()
 
+if(OPENUSD_HAS_CYCLES)
+    install(FILES "${HDCYCLES_DLL}"
+        DESTINATION bin/usd
+        OPTIONAL
+    )
+    install(DIRECTORY "${HDCYCLES_PLUGIN_DIR}"
+        DESTINATION bin/usd
+        OPTIONAL
+    )
+    # Cycles runtime deps (embree4, epoxy, imath, openvdb, OIDN, sycl, etc.)
+    install(DIRECTORY "${CYCLES_INSTALL_DIR}/"
+        DESTINATION bin
+        FILES_MATCHING PATTERN "*.dll"
+        OPTIONAL
+    )
+    # tbb12.dll (used by openvdb/embree4) lives in the precompiled lib tree, not install output
+    install(FILES "${CYCLES_TBB12_DLL}"
+        DESTINATION bin
+        OPTIONAL
+    )
+endif()
+
 # Install Python runtime DLLs required by OpenUSD.
 install(FILES
     "$ENV{LOCALAPPDATA}/Programs/Python/Python312/python312.dll"
@@ -318,11 +474,17 @@ endif()
 message(STATUS "hdArnold support: ${OPENUSD_HAS_ARNOLD}")
 if(OPENUSD_HAS_ARNOLD)
     message(STATUS "hdArnold DLL: ${HDARNOLD_DLL}")
-    message(STATUS "Arnold ai.dll: ${ARNOLD_AI_DLL}")
+    message(STATUS "Arnold runtime DLLs: ${ARNOLD_RUNTIME_DLLS}")
     if(NOT ARNOLD_AI_DLL)
         message(WARNING "hdArnold found but ai.dll not located — set ARNOLD_LOCATION to the MtoA root (e.g. C:/Autodesk/mtoa/5.5.0/2026)")
     endif()
 endif()
+message(STATUS "hdCycles support: ${OPENUSD_HAS_CYCLES}")
+if(OPENUSD_HAS_CYCLES)
+    message(STATUS "Cycles source: ${CMAKE_SOURCE_DIR}/third_party/cycles")
+    message(STATUS "Cycles build: ${CYCLES_BINARY_DIR}")
+    message(STATUS "Cycles install: ${CYCLES_INSTALL_DIR}")
+endif()
 message(STATUS "=======================================")
 message(STATUS "")
 

CMakePresets.json

@@ -13,7 +13,11 @@
         "IMGUI_DIR": "${sourceDir}/third_party/imgui-1.92.7",
         "CMAKE_CXX_STANDARD": "17",
         "CMAKE_CXX_STANDARD_REQUIRED": "ON",
-        "BUILD_TESTS": "ON"
+        "BUILD_TESTS": "ON",
+        "WITH_CYCLES": "ON",
+        "HDARNOLD_ROOT": "E:/library/hdArnold",
+        "ARNOLD_LOCATION": "C:/Autodesk/mtoa/5.5.0/2026",
+        "HDEMBREE_USD_ROOT": "E:/USD_v25.05_embree"
       }
     },
     {