Initial release of the Unity plugin.

PiperOrigin-RevId: 425947505

unity/Runtime/Tools/MjHierarchyTool.cs

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+// Copyright 2019 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.
+
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Linq;
+using UnityEngine;
+
+namespace Mujoco {
+
+// A set of helper methods for working with hierarchies of components.
+public static class MjHierarchyTool {
+
+  public static IEnumerable<MjComponent> LinearizeHierarchyBFS(Transform start) {
+    var open = new Queue<Transform>();
+    open.Enqueue(start);
+    while (open.Count > 0) {
+      var transform = open.Dequeue();
+
+      var components = transform.GetComponents<MjComponent>();
+      foreach (var component in components) {
+        if (component.isActiveAndEnabled) {
+          yield return component;
+        }
+      }
+
+      foreach (Transform child in transform) {
+        open.Enqueue(child);
+      }
+    }
+  }
+
+  // Recurses up the tree (excluding self) and returns the first instance of a MjComponent.
+  public static MjComponent FindParentComponent(MonoBehaviour start) {
+    return FindParentComponent<MjComponent>(start);
+  }
+
+  // This is not equivalent to Unity's GetComponentInParent as it excludes self from the search.
+  public static T FindParentComponent<T>(MonoBehaviour start) where T : MonoBehaviour {
+    if (start.transform.parent == null) {
+      return null;
+    }
+    var loopTransform = start.transform.parent;
+    T result = loopTransform.GetComponent<T>();
+    while (result == null && loopTransform.parent != null) {
+      loopTransform = loopTransform.parent;
+      result = loopTransform.GetComponent<T>();
+    }
+    return result;
+  }
+
+  public static List<T> GetComponentsInImmediateChildren<T>(Transform parent)
+      where T : MonoBehaviour {
+    var components = new List<T>();
+    foreach (Transform child in parent) {
+      components.AddRange(child.gameObject.GetComponents<T>());
+    }
+    return components;
+  }
+
+  // Finds a single component that matches both the type and the name criteria.
+  public static T FindComponentOfTypeAndName<T>(string name) where T : MjComponent {
+    var components = UnityEngine.Object.FindObjectsOfType<T>().Where(
+        component => component.gameObject.name == name);
+    var numComponents = components.Count();
+    if (components == null || numComponents == 0) {
+      throw new ArgumentException($"No components named '{name}' were found.");
+    }
+    if (numComponents > 1) {
+      throw new ArgumentException($"More than one component named '{name}' was found.");
+    }
+    return components.FirstOrDefault() as T;
+  }
+}
+}