Add mj_loadUSD function. Change simulate to use that instead of manual spec compilation.

PiperOrigin-RevId: 780608874
Change-Id: I333238c756fe76b371518a7cdf9452b93da3540a

src/experimental/usd/CMakeLists.txt

@@ -16,7 +16,6 @@
 # Plugin target names (used for library and plugInfo.json)
 set(MJCF_PLUGIN_TARGET_NAME usdMjcf)
 set(MJC_PHYSICS_PLUGIN_TARGET_NAME mjcPhysics)
-set(MJ_USD_TARGET_NAME mj_usd)
 
 # Installation directory for USD plugins
 set(MJ_USD_INSTALL_DIR_LIB ${CMAKE_INSTALL_LIBDIR}/mujocoUsd)
@@ -187,14 +186,12 @@ set_target_properties(${MJC_PHYSICS_PLUGIN_TARGET_NAME} PROPERTIES
   ${DEFAULT_CXX_VISIBILITY_PROPS}
 )
 target_include_directories(${MJC_PHYSICS_PLUGIN_TARGET_NAME} PUBLIC
-  "${CMAKE_CURRENT_SOURCE_DIR}/mjcPhysics"
+  $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/../../../include>
 )
 
 ## mj_usd
 
-add_library(${MJ_USD_TARGET_NAME} SHARED)
-add_library(mujoco::usd ALIAS ${MJ_USD_TARGET_NAME})
-target_sources(${MJ_USD_TARGET_NAME} PRIVATE
+target_sources(mujoco PRIVATE
   kinematic_tree.cc
   kinematic_tree.h
   layer_sink.cc
@@ -212,8 +209,6 @@ if (USD_DIR)
 
   target_link_libraries(${MJC_PHYSICS_PLUGIN_TARGET_NAME} PRIVATE
     ${OPENUSD_CORE_LIBS}
-    mujoco
-    tinyxml2
   )
 
   target_link_libraries(${MJCF_PLUGIN_TARGET_NAME} PRIVATE
@@ -223,10 +218,8 @@ if (USD_DIR)
     ${MJC_PHYSICS_PLUGIN_TARGET_NAME}
   )
 
-  target_link_libraries(${MJ_USD_TARGET_NAME} PUBLIC
+  target_link_libraries(mujoco PUBLIC
     ${OPENUSD_CORE_LIBS}
-    mujoco
-    tinyxml2
     ${MJC_PHYSICS_PLUGIN_TARGET_NAME}
   )
 elseif (HOUDINI_HFS_DIR)
@@ -237,11 +230,9 @@ elseif (HOUDINI_HFS_DIR)
   # so we need to manually link all the required libraries.
   configure_houdini_target(${MJC_PHYSICS_PLUGIN_TARGET_NAME} PRIVATE PRIVATE)
   configure_houdini_target(${MJCF_PLUGIN_TARGET_NAME} PRIVATE PRIVATE)
-  configure_houdini_target(${MJ_USD_TARGET_NAME} PUBLIC PUBLIC)
 
   # Re-add inter-plugin dependencies after Houdini-specific linking
   target_link_libraries(${MJCF_PLUGIN_TARGET_NAME} PRIVATE ${MJC_PHYSICS_PLUGIN_TARGET_NAME})
-  target_link_libraries(${MJ_USD_TARGET_NAME} PUBLIC ${MJC_PHYSICS_PLUGIN_TARGET_NAME})
 
 endif()
 
@@ -272,6 +263,6 @@ install(FILES
 install(TARGETS
   ${MJCF_PLUGIN_TARGET_NAME}
   ${MJC_PHYSICS_PLUGIN_TARGET_NAME}
-  ${MJ_USD_TARGET_NAME}
+  EXPORT ${PROJECT_NAME}
   LIBRARY DESTINATION ${MJ_USD_INSTALL_DIR_LIB}
 )

src/experimental/usd/layer_sink.cc

@@ -41,8 +41,7 @@
 
 PXR_NAMESPACE_OPEN_SCOPE
 TF_DEFINE_PRIVATE_TOKENS(_layer_sink_tokens,
-                         ((xformOpTransform,
-                           "xformOp:transform:mujoco"))(Xform));
+                         ((xformOpTransform, "xformOp:transform:mujoco")));
 PXR_NAMESPACE_CLOSE_SCOPE
 
 namespace {

src/xml/xml_api.cc

@@ -34,6 +34,10 @@
 #include "xml/xml.h"
 #include "xml/xml_native_reader.h"
 #include "xml/xml_util.h"
+#if defined(mjUSEUSD)
+#include <mujoco/experimental/usd/usd.h>
+#include <pxr/usd/usd/stage.h>
+#endif
 
 //---------------------------------- Globals -------------------------------------------------------
 
@@ -126,7 +130,36 @@ mjModel* mj_loadXML(const char* filename, const mjVFS* vfs,
   return m;
 }
 
+#if defined(mjUSEUSD)
+//  parse USD file, compile it, and return low-level model.
+//  if vfs is not NULL, look up files in vfs before reading from disk
+//  error can be NULL; otherwise assumed to have size error_sz
+mjModel* mj_loadUSD(const char* filename, const mjVFS* vfs, char* error, int error_sz) {
+  auto stage = pxr::UsdStage::Open(filename);
 
+  if (stage == nullptr) {
+    mjCopyError(error, "Failed to load USD stage from file.", error_sz);
+    return nullptr;
+  }
+
+  // Parse USD into mjSpec.
+  std::unique_ptr<mjSpec, std::function<void(mjSpec*)> > spec(
+    mj_parseUSDStage(stage),
+    [](mjSpec* s) {
+      mj_deleteSpec(s);
+    });
+
+  // Compile new model.
+  mjModel* m = mj_compile(spec.get(), vfs);
+  if (!m) {
+    mjCopyError(error, mjs_getError(spec.get()), error_sz);
+    return nullptr;
+  }
+
+  GetGlobalModel().Set(spec.release());
+  return m;
+}
+#endif
 
 // update XML data structures with info from low-level model, save as MJCF
 //  returns 1 if successful, 0 otherwise