Move OpenUSD parsing to usd_decoder

Add usd_decoder to mujoco/plugin. - Previously was src/experimental/usd/usd_to_mjspec.cc, now that same spec is returned by the plugin. PiperOrigin-RevId: 854350962 Change-Id: Ia980190a557c50ce8197980922a2594b613859b4
2026-01-09 14:47:37 -08:00
parent 64a2345c07
commit a5dc57c0c3
17 changed files with 270 additions and 317 deletions
@@ -0,0 +1,51 @@
+// Copyright 2025 DeepMind Technologies Limited
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef MUJOCO_PLUGIN_USD_DECODER_KINEMATIC_TREE_H_
+#define MUJOCO_PLUGIN_USD_DECODER_KINEMATIC_TREE_H_
+
+#include <memory>
+#include <vector>
+
+#include <pxr/usd/sdf/path.h>
+#include <pxr/usd/usdPhysics/joint.h>
+
+// A struct to represent a node in the kinematic tree.
+// Using a struct with a vector of children preserves the order of bodies,
+// which is important for things like keyframes and policy compatibility.
+struct Node {
+  pxr::SdfPath body_path;
+  pxr::SdfPath physics_scene;
+  std::vector<pxr::SdfPath> actuators;
+  std::vector<pxr::SdfPath> joints;
+  std::vector<pxr::SdfPath> visual_gprims;
+  std::vector<pxr::SdfPath> colliders;
+  std::vector<pxr::SdfPath> sites;
+  std::vector<pxr::SdfPath> tendons;
+  std::vector<pxr::SdfPath> keyframes;
+  std::vector<std::unique_ptr<Node>> children;
+};
+
+// A kinematic edge represents a joint.
+using JointVec = std::vector<pxr::UsdPhysicsJoint>;
+
+// Builds a single kinematic tree from a list of directed edges.
+// The DFS order of bodies in the tree is determined by the order of bodies in
+// `all_body_paths`.
+// All bodies, including static and floating-base bodies, are organized under a
+// single world root. An empty 'from' path in an edge represents the world body.
+// Returns the root of the kinematic tree, or `nullptr` for invalid structures.
+std::unique_ptr<Node> BuildKinematicTree(const pxr::UsdStageRefPtr stage);
+
+#endif  // MUJOCO_PLUGIN_USD_DECODER_KINEMATIC_TREE_H_