Initial release of the Unity plugin.

PiperOrigin-RevId: 425947505

unity/Runtime/Components/MjGizmos.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 UnityEngine;
+
+namespace Mujoco {
+
+// Additional Debug Gizmos.
+public static class MjGizmos {
+
+  private const float _vectorPerpendicularityMagnitudeThreshold = 1e-6f;
+
+  public static int NumCircleSegments = 32;
+
+  private static Vector3[] _circumferenceVertices = new Vector3[] {
+    Vector3.right, -Vector3.right, Vector3.forward, -Vector3.forward,
+  };
+
+  public static Action<Vector3 /*from*/, Vector3 /*to*/> DrawLine { get; set; } = Gizmos.DrawLine;
+
+  public static Action<Vector3 /*position*/, float /*radius*/, Vector3 /*axis*/, float /*length*/,
+                       float /*startAngle*/> DrawArc { get; set; } = MjGizmos.DrawArcInternal;
+
+  // Draws a wireframe capsule of the specified radius and height.
+  // The capsule's height will be aligned with the global Y axis.
+  // The specified height represents the height of the cylinder between two hemisphere bases.
+  public static void DrawWireCapsule(Vector3 position, float radius, float height) {
+    var offset = DrawHollowWireCylinder(position, radius, height);
+    // Arches marking the bases of the capsule.
+    DrawArc(position - offset, radius, Vector3.right, 0.5f, 0.0f);
+    DrawArc(position + offset, radius, Vector3.right, 0.5f, 180.0f);
+    DrawArc(position + offset, radius, Vector3.forward, 0.5f, -90.0f);
+    DrawArc(position - offset, radius, Vector3.forward, 0.5f, 90.0f);
+  }
+
+  // Draws a wireframe cylinder of the specified radius and height.
+  // The cylinder's height will be aligned with the global Y axis.
+  public static void DrawWireCylinder(Vector3 position, float radius, float height) {
+    var offset = DrawHollowWireCylinder(position, radius, height);
+    // Lines marking the bases of the cylinder.
+    for (var i = 0; i < _circumferenceVertices.Length / 2; ++i) {
+      var vertex = _circumferenceVertices[i * 2] * radius;
+      var nextVertex = _circumferenceVertices[i * 2 + 1] * radius;
+      DrawLine(position + offset + vertex, position + offset + nextVertex);
+      DrawLine(position - offset + vertex, position - offset + nextVertex);
+    }
+  }
+
+  private static Vector3 DrawHollowWireCylinder(Vector3 position, float radius, float height) {
+    var offset = Vector3.up * (height * 0.5f);
+    // Cylinder bases.
+    DrawArc(position + offset, radius, Vector3.up, 1.0f, 0.0f);
+    DrawArc(position - offset, radius, Vector3.up, 1.0f, 0.0f);
+    // Lines marking the sides of the cylinder.
+    for (var i = 0; i < _circumferenceVertices.Length; ++i) {
+      // Lines marking the sides of the cylinder.
+      var vertex = _circumferenceVertices[i] * radius;
+      DrawLine(position + offset + vertex, position - offset + vertex);
+    }
+    return offset;
+  }
+
+  // Draws an arc in the XZ plane.
+  // 'length' parameter, in range (0, 1], allows to define how much of the circumference should be
+  // drawn. In other words, it allows to draw arbitrary arcs.
+  // Two additional parameters, 'axis' and 'startAngle', allow to orient the figure without having
+  // to manipulate the value of Gizmos.matrix.
+  public static void DrawArcInternal(
+      Vector3 position, float radius, Vector3 axis, float length, float startAngle) {
+    var deltaAngle = 360.0f / NumCircleSegments;
+    var numSegments = Math.Ceiling(length * NumCircleSegments);
+
+    var perpendicular = Vector3.Cross(axis, Vector3.right);
+    if (perpendicular.magnitude <= _vectorPerpendicularityMagnitudeThreshold) {
+      perpendicular = Vector3.Cross(axis, Vector3.up);
+    }
+    perpendicular.Normalize();
+
+    var offset = perpendicular * radius;
+    var start = Quaternion.AngleAxis(startAngle, axis) * offset;
+    var angle = startAngle + deltaAngle;
+
+    for (var segment = 0; segment < numSegments; ++segment, angle += deltaAngle) {
+      var end = Quaternion.AngleAxis(angle, axis) * offset;
+      DrawLine(position + start, position + end);
+      start = end;
+    }
+  }
+
+  public static void DrawWirePlane(Vector3 position, float width, float height) {
+    var quadPoints = new Vector3[] {
+      new Vector3(-0.5f * width, 0, -0.5f * height),
+      new Vector3(0.5f * width, 0, -0.5f * height),
+      new Vector3(0.5f * width, 0, 0.5f * height),
+      new Vector3(-0.5f * width, 0, 0.5f * height),
+      new Vector3(-0.5f * width, 0, -0.5f * height),
+      new Vector3(0.5f * width, 0, 0.5f * height),
+    };
+    for (var i = 0; i < quadPoints.Length - 1; ++i) {
+      DrawLine(position + quadPoints[i], position + quadPoints[i + 1]);
+    }
+  }
+}
+}