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

PiperOrigin-RevId: 780608874
Change-Id: I333238c756fe76b371518a7cdf9452b93da3540a

CMakeLists.txt

@@ -202,6 +202,7 @@ if(MUJOCO_BUILD_EXAMPLES)
 endif()
 
 if(MUJOCO_WITH_USD)
+  target_compile_definitions(mujoco PUBLIC mjUSEUSD)
   add_subdirectory(src/experimental/usd)
 endif()
 

include/mujoco/experimental/usd/usd.h

@@ -18,6 +18,12 @@
 #include <mujoco/mujoco.h>
 #include <pxr/usd/usd/common.h>
 
+// Given a USD file parse to a spec, then compile and return the low-level model.
+//
+// Particular care is taken for physics data to be lossless but visual
+// data such as materials may be lossy.
+MJAPI mjModel* mj_loadUSD(const char* filename, const mjVFS* vfs, char* error, int error_sz);
+
 // Given a USD stage, this function will do a best effort conversion to
 // mjSpec.
 //

simulate/CMakeLists.txt

@@ -177,7 +177,6 @@ if(SIMULATE_BUILD_EXECUTABLE)
   if (MUJOCO_WITH_USD)
     target_link_libraries(
       simulate
-      mujoco::usd
       mujoco::usd::mjcf
     )
   endif()
@@ -249,7 +248,7 @@ if(SIMULATE_BUILD_EXECUTABLE)
     )
 
     if (MUJOCO_WITH_USD)
-      target_compile_definitions(simulate PUBLIC SIMULATE_WITH_USD)
+      target_compile_definitions(simulate PUBLIC mjUSEUSD)
 
       # Add support to RPATH for the samples.
       target_add_rpath(

simulate/main.cc

@@ -25,11 +25,8 @@
 #include <string>
 #include <thread>
 
-#if defined(SIMULATE_WITH_USD)
+#if defined(mjUSEUSD)
 #include <mujoco/experimental/usd/usd.h>
-#include <pxr/pxr.h>
-#include <pxr/usd/usd/common.h>
-#include <pxr/usd/usd/stage.h>
 #endif
 #include <mujoco/mujoco.h>
 #include "glfw_adapter.h"
@@ -244,34 +241,10 @@ mjModel* LoadModel(const char* file, mj::Simulate& sim) {
     if (!mnew) {
       mju::strcpy_arr(loadError, "could not load binary model");
     }
-#if defined(SIMULATE_WITH_USD)
+#if defined(mjUSEUSD)
   } else if (extension == ".usda" || extension == ".usd" ||
              extension == ".usdc" || extension == ".usdz" ) {
-    auto stage = pxr::UsdStage::Open(filename);
+    mnew = mj_loadUSD(filename, nullptr, loadError, kErrorLength);
-    if (!stage) {
-      mju::strcpy_arr(loadError, "could not open USD stage");
-    } else {
-      mjSpec* spec = mj_parseUSDStage(stage);
-      if (!spec) {
-        mju::strcpy_arr(loadError, "could not parse USD stage to mjSpec");
-      } else {
-        mjModel* model = mj_compile(spec, nullptr);
-        if (!model) {
-          mju::strcpy_arr(loadError,
-                          "could not compile USD parsed mjSpec to mjModel:\n");
-          mju::strcat_arr(loadError, mjs_getError(spec));
-        } else {
-          // handle compile warning
-          if (mjs_isWarning(spec)) {
-            mju::strcpy_arr(
-                loadError,
-                "warning while compiling USD parsed mjSpec to mjModel:\n");
-            mju::strcat_arr(loadError, mjs_getError(spec));
-          }
-        }
-        mnew = model;
-      }
-    }
 #endif
   } else {
     mnew = mj_loadXML(filename, nullptr, loadError, kErrorLength);
@@ -537,7 +510,7 @@ int main(int argc, char** argv) {
   // scan for libraries in the plugin directory to load additional plugins
   scanPluginLibraries();
 
-#if defined(SIMULATE_WITH_USD)
+#if defined(mjUSEUSD)
   // If USD is used, print the version.
   std::printf("OpenUSD version v%d.%02d\n", PXR_MINOR_VERSION, PXR_PATCH_VERSION);
 #endif

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)
+target_sources(mujoco PRIVATE
-add_library(mujoco::usd ALIAS ${MJ_USD_TARGET_NAME})
-target_sources(${MJ_USD_TARGET_NAME} 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,
+                         ((xformOpTransform, "xformOp:transform:mujoco")));
-                           "xformOp:transform:mujoco"))(Xform));
 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

test/xml/testdata/simple_hinge.usda

@@ -0,0 +1,71 @@
+#usda 1.0
+(
+    endTimeCode = 1
+    framesPerSecond = 24
+    metersPerUnit = 1
+    startTimeCode = 1
+    timeCodesPerSecond = 24
+    upAxis = "Y"
+)
+
+def Xform "World"
+{
+    def Xform "Axle" (
+        prepend apiSchemas = ["PhysicsRigidBodyAPI", "PhysicsArticulationRootAPI"]
+    )
+    {
+        matrix4d xformOp:transform:set_initial_pos = ( (1, 0, 0, 0), (0, 0.9999197811020019, -0.012666150201413267, 0), (0, 0.012666150201413267, 0.9999197811020019, 0), (0, 0.012296309694647789, 0.970723032951355, 1) )
+        uniform token[] xformOpOrder = ["xformOp:transform:set_initial_pos"]
+
+        def Xform "Rod" (
+            prepend apiSchemas = ["PhysicsRigidBodyAPI"]
+        )
+        {
+            matrix4d xformOp:transform:set_initial_rod_pos = ( (1, 0, 0, 0), (0, 0.3255001489278845, 0.9455419890453967, 0), (0, -0.9455419890453967, 0.3255001489278845, 0), (0, 0.47277099452269833, -0.1627500744639423, 1) )
+            uniform token[] xformOpOrder = ["xformOp:transform:set_initial_rod_pos"]
+
+            def Cylinder "Geometry" (
+                prepend apiSchemas = ["PhysicsCollisionAPI"]
+            )
+            {
+                token axis = "Z"
+                float3[] extent = [(-0.01, -0.01, -0.5), (0.01, 0.01, 0.5)]
+                double height = 1
+                double radius = 0.01
+                matrix4d xformOp:transform = ( (1, 0, 0, 0), (0, 1, 0, 0), (0, 0, 1, 0), (0, 0, -0.03546595561524429, 1) )
+                uniform token[] xformOpOrder = ["xformOp:transform"]
+            }
+
+            def PhysicsRevoluteJoint "HingeJoint" (
+                prepend apiSchemas = ["PhysicsActuatorAPI"]
+            )
+            {
+                rel physics:body0 = </World/Axle>
+                rel physics:body1 = </World/Axle/Rod>
+                point3f physics:localPos0 = (0, 0, 0)
+                point3f physics:localPos1 = (0, 0, 0.5)
+                quatf physics:localRot0 = (0, 1, 0, 0)
+                quatf physics:localRot1 = (0, 1, 0, 0)
+            }
+        }
+
+        def Cylinder "Geometry" (
+            prepend apiSchemas = ["PhysicsCollisionAPI"]
+        )
+        {
+            token axis = "Z"
+            float3[] extent = [(-0.01, -0.01, -0.1), (0.01, 0.01, 0.1)]
+            double height = 0.2
+            double radius = 0.01
+            matrix4d xformOp:transform = ( (0, 0, -1, 0), (0, 1, -0, 0), (1, 0, -0, 0), (0, 0, -0, 1) )
+            uniform token[] xformOpOrder = ["xformOp:transform"]
+        }
+
+        def PhysicsFixedJoint "FixedJoint"
+        {
+            rel physics:body0 = None
+            rel physics:body1 = </World/Axle>
+        }
+    }
+}
+