Add geometry classes (#1766)

These classes introduce ways to represent poses and provide easy ways to transform, rotate, and translate poses across 2d space. This classes will be especially useful for a planned odometry and kinematics suite.

Furthermore, these classes can also be used to simply represent waypoints on a field, do superstructure motion planning, etc.

wpilibc/src/main/native/include/frc/geometry/Transform2d.h

@@ -0,0 +1,60 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2019 FIRST. All Rights Reserved.                             */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#pragma once
+
+#include "Translation2d.h"
+
+namespace frc {
+
+class Pose2d;
+
+/**
+ * Represents a transformation for a Pose2d.
+ */
+class Transform2d {
+ public:
+  /**
+   * Constructs the transform that maps the initial pose to the final pose.
+   *
+   * @param initial The initial pose for the transformation.
+   * @param final The final pose for the transformation.
+   */
+  Transform2d(Pose2d initial, Pose2d final);
+
+  /**
+   * Constructs a transform with the given translation and rotation components.
+   *
+   * @param translation Translational component of the transform.
+   * @param rotation Rotational component of the transform.
+   */
+  Transform2d(Translation2d translation, Rotation2d rotation);
+
+  /**
+   * Constructs the identity transform -- maps an initial pose to itself.
+   */
+  constexpr Transform2d() = default;
+
+  /**
+   * Returns the translation component of the transformation.
+   *
+   * @return Reference to the translational component of the transform.
+   */
+  const Translation2d& Translation() const { return m_translation; }
+
+  /**
+   * Returns the rotational component of the transformation.
+   *
+   * @return Reference to the rotational component of the transform.
+   */
+  const Rotation2d& Rotation() const { return m_rotation; }
+
+ private:
+  Translation2d m_translation;
+  Rotation2d m_rotation;
+};
+}  // namespace frc