Merge remote-tracking branch 'origin/feature/SO3_refactor' into feature/ImuFactorPush2

gtsam/geometry/SO3.cpp

@@ -25,15 +25,9 @@
 
 namespace gtsam {
 
-/* ************************************************************************* */
-// Functor implementing Exponential map
-struct ExpmapImpl {
-  const double theta2;
-  Matrix3 W, K, KK;
-  bool nearZero;
-  double theta, sin_theta, one_minus_cos;  // only defined if !nearZero
+namespace so3 {
 
-  void init() {
+void ExpmapFunctor::init() {
   nearZero = (theta2 <= std::numeric_limits<double>::epsilon());
   if (nearZero) return;
   theta = std::sqrt(theta2);  // rotation angle
@@ -42,8 +36,7 @@ struct ExpmapImpl {
   one_minus_cos = 2.0 * s2 * s2;  // numerically better than [1 - cos(theta)]
 }
 
-  // Constructor with element of Lie algebra so(3)
-  ExpmapImpl(const Vector3& omega) : theta2(omega.dot(omega)) {
+ExpmapFunctor::ExpmapFunctor(const Vector3& omega) : theta2(omega.dot(omega)) {
   const double wx = omega.x(), wy = omega.y(), wz = omega.z();
   W << 0.0, -wz, +wy, +wz, 0.0, -wx, -wy, +wx, 0.0;
   init();
@@ -54,8 +47,8 @@ struct ExpmapImpl {
   }
 }
 
-  // Constructor with axis-angle
-  ExpmapImpl(const Vector3& axis, double angle) : theta2(angle * angle) {
+ExpmapFunctor::ExpmapFunctor(const Vector3& axis, double angle)
+    : theta2(angle * angle) {
   const double ax = axis.x(), ay = axis.y(), az = axis.z();
   K << 0.0, -az, +ay, +az, 0.0, -ax, -ay, +ax, 0.0;
   W = K * angle;
@@ -66,48 +59,28 @@ struct ExpmapImpl {
   }
 }
 
-  // Rodrgues formula
-  SO3 expmap() const {
+SO3 ExpmapFunctor::expmap() const {
   if (nearZero)
     return I_3x3 + W;
   else
     return I_3x3 + sin_theta * K + one_minus_cos * K * K;
 }
-};
 
-/* ************************************************************************* */
-SO3 SO3::AxisAngle(const Vector3& axis, double theta) {
-  return ExpmapImpl(axis, theta).expmap();
-}
-
-/* ************************************************************************* */
-// Functor that implements Exponential map *and* its derivatives
-struct DexpImpl : ExpmapImpl {
-  const Vector3 omega;
-  double a, b;  // constants used in dexp and applyDexp
-
-  // Constructor with element of Lie algebra so(3)
-  DexpImpl(const Vector3& omega) : ExpmapImpl(omega), omega(omega) {
+DexpFunctor::DexpFunctor(const Vector3& omega)
+    : ExpmapFunctor(omega), omega(omega) {
   if (nearZero) return;
   a = one_minus_cos / theta;
   b = 1.0 - sin_theta / theta;
 }
 
-  // NOTE(luca): Right Jacobian for Exponential map in SO(3) - equation
-  // (10.86) and following equations in G.S. Chirikjian, "Stochastic Models,
-  // Information Theory, and Lie Groups", Volume 2, 2008.
-  //   expmap(omega + v) \approx expmap(omega) * expmap(dexp * v)
-  // This maps a perturbation v in the tangent space to
-  // a perturbation on the manifold Expmap(dexp * v) */
-  SO3 dexp() const {
+SO3 DexpFunctor::dexp() const {
   if (nearZero)
     return I_3x3 - 0.5 * W;
   else
     return I_3x3 - a * K + b * KK;
 }
 
-  // Just multiplies with dexp()
-  Vector3 applyDexp(const Vector3& v, OptionalJacobian<3, 3> H1,
+Vector3 DexpFunctor::applyDexp(const Vector3& v, OptionalJacobian<3, 3> H1,
                                OptionalJacobian<3, 3> H2) const {
   if (nearZero) {
     if (H1) *H1 = 0.5 * skewSymmetric(v);
@@ -127,26 +100,31 @@ struct DexpImpl : ExpmapImpl {
   if (H2) *H2 = dexp();
   return v - a * Kv + b * KKv;
 }
-};
+
+}  // namespace so3
 
 /* ************************************************************************* */
+SO3 SO3::AxisAngle(const Vector3& axis, double theta) {
+  return so3::ExpmapFunctor(axis, theta).expmap();
+}
+
 SO3 SO3::Expmap(const Vector3& omega, ChartJacobian H) {
   if (H) {
-    DexpImpl impl(omega);
+    so3::DexpFunctor impl(omega);
     *H = impl.dexp();
     return impl.expmap();
   } else
-    return ExpmapImpl(omega).expmap();
+    return so3::ExpmapFunctor(omega).expmap();
 }
 
 Matrix3 SO3::ExpmapDerivative(const Vector3& omega) {
-  return DexpImpl(omega).dexp();
+  return so3::DexpFunctor(omega).dexp();
 }
 
 Vector3 SO3::ApplyExpmapDerivative(const Vector3& omega, const Vector3& v,
                                    OptionalJacobian<3, 3> H1,
                                    OptionalJacobian<3, 3> H2) {
-  return DexpImpl(omega).applyDexp(v, H1, H2);
+  return so3::DexpFunctor(omega).applyDexp(v, H1, H2);
 }
 
 /* ************************************************************************* */

gtsam/geometry/SO3.h

@@ -135,6 +135,54 @@ public:
   /// @}
 };
 
+// This namespace exposes two functors that allow for saving computation when
+// exponential map and its derivatives are needed at the same location in so<3>
+namespace so3 {
+
+/// Functor implementing Exponential map
+class ExpmapFunctor {
+ protected:
+  const double theta2;
+  Matrix3 W, K, KK;
+  bool nearZero;
+  double theta, sin_theta, one_minus_cos;  // only defined if !nearZero
+
+  void init();
+
+ public:
+  /// Constructor with element of Lie algebra so(3)
+  ExpmapFunctor(const Vector3& omega);
+
+  /// Constructor with axis-angle
+  ExpmapFunctor(const Vector3& axis, double angle);
+
+  /// Rodrgues formula
+  SO3 expmap() const;
+};
+
+/// Functor that implements Exponential map *and* its derivatives
+class DexpFunctor : public ExpmapFunctor {
+  const Vector3 omega;
+  double a, b;
+
+ public:
+  /// Constructor with element of Lie algebra so(3)
+  DexpFunctor(const Vector3& omega);
+
+  // NOTE(luca): Right Jacobian for Exponential map in SO(3) - equation
+  // (10.86) and following equations in G.S. Chirikjian, "Stochastic Models,
+  // Information Theory, and Lie Groups", Volume 2, 2008.
+  //   expmap(omega + v) \approx expmap(omega) * expmap(dexp * v)
+  // This maps a perturbation v in the tangent space to
+  // a perturbation on the manifold Expmap(dexp * v) */
+  SO3 dexp() const;
+
+  /// Multiplies with dexp(), with optional derivatives
+  Vector3 applyDexp(const Vector3& v, OptionalJacobian<3, 3> H1,
+                    OptionalJacobian<3, 3> H2) const;
+};
+}  //  namespace so3
+
 template<>
 struct traits<SO3> : public internal::LieGroup<SO3> {
 };