Adds bounds retrieval for TimeVarying grid class. (#508)

* Adds bounds retrieval for TimeVarying grid class.

This is required for visualization purposes.

Signed-off-by: Arjo Chakravarty <[email protected]>

include/gz/math/TimeVaryingVolumetricGrid.hh

@@ -53,6 +53,10 @@ class TimeVaryingVolumetricGrid
   /// \param[in] _pos - The position of the point we want to query
   public: std::optional<V> LookUp(const S &_session, const Vector3<P> &_pos)
     const;
+
+  /// \brief Get the bounds of this grid field at given time.
+  /// \return A pair of vectors. All zeros if session is invalid.
+  public: std::pair<Vector3<V>, Vector3<V>> Bounds(const S &_session) const;
 };
 
 /// \brief Specialization of TimeVaryingVolumetricGrid which loads the whole of
@@ -93,6 +97,14 @@ class TimeVaryingVolumetricGrid<T, V, InMemorySession<T, P>, P>
     return result;
   }
 
+  /// \brief Get the bounds of this grid field at given time.
+  /// \return A pair of vectors. All zeros if session is invalid.
+  public: std::pair<Vector3<V>, Vector3<V>> Bounds(
+    const InMemorySession<T, P> &_session) const
+  {
+    return indices.Bounds(_session);
+  }
+
   /// Buffer for values being stored
   private: std::vector<V> values;
 

include/gz/math/TimeVaryingVolumetricGridLookupField.hh

@@ -87,6 +87,10 @@ namespace gz
         const std::vector<X> &_values2,
         const X _default = X(0)
       ) const;
+
+      /// \brief Get the bounds of this grid field.
+      /// \return A pair of vectors.
+      public: std::pair<Vector3<V>, Vector3<V>> Bounds(const S &_session);
     };
 
     /// \brief An in-memory session. Loads the whole dataset in memory and
@@ -285,6 +289,22 @@ namespace gz
         // Return nullopt if we are out of range
         return std::nullopt;
       }
+
+      /// \brief Get the bounds of this grid field.
+      /// \return A pair of vectors. All zeros if session is invalid.
+      public: std::pair<Vector3<V>, Vector3<V>> Bounds(
+        const InMemorySession<T, V> &_session) const
+      {
+        if (_session.iter == this->gridFields.end())
+        {
+          // Out of bounds
+          return std::pair<Vector3<T>, Vector3<T>>(
+            Vector3<T>{0, 0, 0}, Vector3<T>{0, 0, 0}
+          );
+        }
+        return _session.iter->second.Bounds();
+      }
+
       private: std::map<T, VolumetricGridLookupField<V>> gridFields;
     };
   }

include/gz/math/VolumetricGridLookupField.hh

@@ -18,8 +18,9 @@
 #ifndef GZ_MATH_VOLUMETRIC_GRID_LOOKUP_FIELD_HH_
 #define GZ_MATH_VOLUMETRIC_GRID_LOOKUP_FIELD_HH_
 
-#include <vector>
 #include <optional>
+#include <utility>
+#include <vector>
 
 #include <gz/math/Vector3.hh>
 #include <gz/math/detail/InterpolationPoint.hh>
@@ -262,6 +263,23 @@ namespace gz
           }
         }
 
+        /// \brief Get the bounds of this grid field.
+        /// \return A pair of vectors.
+        public: std::pair<Vector3<T>, Vector3<T>> Bounds() const
+        {
+          return std::pair<Vector3<T>, Vector3<T>>(
+            Vector3<T>{
+              x_indices_by_lat.MinKey(),
+              y_indices_by_lon.MinKey(),
+              z_indices_by_depth.MinKey()
+            },
+            Vector3<T>{
+              x_indices_by_lat.MaxKey(),
+              y_indices_by_lon.MaxKey(),
+              z_indices_by_depth.MaxKey()
+            });
+        }
+
       };
     }
   }

include/gz/math/detail/AxisIndex.hh

@@ -45,6 +45,30 @@ namespace gz
         /// \brief Number of indices
         private: int numIndices{0};
 
+        /// \brief Minimum key
+        /// \return the minimum key or zero if the axis is empty.
+        public: T MinKey() const
+        {
+          auto key = axisIndex.begin();
+          if (key == axisIndex.end())
+          {
+            return T(0);
+          }
+          return key->first;
+        }
+
+        /// \brief Maximum key
+        /// \return the maximum key or zero if the axis is empty.
+        public: T MaxKey() const
+        {
+          auto key = axisIndex.rbegin();
+          if (key == axisIndex.rend())
+          {
+            return T(0);
+          }
+          return key->first;
+        }
+
         /// \brief Register the existance of a measurement at _value.
         /// \param[in] _value The position of the measurement.
         public: void AddIndexIfNotFound(T _value)

src/TimeVaryingVolumetricGrid_TEST.cc

@@ -63,3 +63,55 @@ TEST(TimeVaryingVolumetricGridTest, TestConstruction)
   val = grid.LookUp(new_sess.value(), Vector3d{2.5, 2.5, 2.5});
   ASSERT_FALSE(val.has_value());
 }
+
+/////////////////////////////////////////////////
+TEST(TimeVaryingVolumetricGridTest, TestBounds)
+{
+  InMemoryTimeVaryingVolumetricGridFactory<double, double> gridFactory;
+
+  for (double t = 0; t <= 1; t+=0.2)
+  {
+    for (double x = -1; x <= 1; x+=0.5)
+    {
+      for (double y = -1; y <= 1; y+=0.5)
+      {
+        for (double z = -1; z <= 1; z+=0.5)
+        {
+          gridFactory.AddPoint(t, Vector3d{x, y, z}, t);
+        }
+      }
+    }
+  }
+
+  auto grid = gridFactory.Build();
+  auto session = grid.CreateSession();
+
+  auto [min, max] = grid.Bounds(session);
+
+  ASSERT_NEAR(min.X(), -1.0, 1e-6);
+  ASSERT_NEAR(min.Y(), -1.0, 1e-6);
+  ASSERT_NEAR(min.Z(), -1.0, 1e-6);
+
+  ASSERT_NEAR(max.X(), 1.0, 1e-6);
+  ASSERT_NEAR(max.Y(), 1.0, 1e-6);
+  ASSERT_NEAR(max.Z(), 1.0, 1e-6);
+}
+
+/////////////////////////////////////////////////
+TEST(TimeVaryingVolumetricGridTest, TestEmptyGrid)
+{
+  InMemoryTimeVaryingVolumetricGridFactory<double, double> gridFactory;
+
+  auto grid = gridFactory.Build();
+  auto session = grid.CreateSession();
+
+  auto [min, max] = grid.Bounds(session);
+
+  ASSERT_NEAR(min.X(), 0, 1e-6);
+  ASSERT_NEAR(min.Y(), 0, 1e-6);
+  ASSERT_NEAR(min.Z(), 0, 1e-6);
+
+  ASSERT_NEAR(max.X(), 0, 1e-6);
+  ASSERT_NEAR(max.Y(), 0, 1e-6);
+  ASSERT_NEAR(max.Z(), 0, 1e-6);
+}

src/VolumetricGridLookupField_TEST.cc

@@ -182,12 +182,15 @@ TEST(VolumetricGridLookupField, CheckTrilinearInterpolationBoxEightPoints)
   }
 }
 
-
 TEST(VolumetricGridLookupField, AxisIndexTest)
 {
   AxisIndex<double> axis;
+  EXPECT_EQ(axis.MinKey(), 0.0);
+  EXPECT_EQ(axis.MaxKey(), 0.0);
   axis.AddIndexIfNotFound(300);
   axis.AddIndexIfNotFound(300);
+  EXPECT_EQ(axis.MinKey(), 300.0);
+  EXPECT_EQ(axis.MaxKey(), 300.0);
   EXPECT_EQ(axis.GetNumUniqueIndices(), 1UL);
   EXPECT_EQ(axis.GetIndex(300).value(), 0UL);
   EXPECT_EQ(axis.GetIndex(200).has_value(), false);