Improves Symmetric ICP estimation

Improves the Symmetric ICP estimation by making minor adjustments to variable declarations for better code clarity.

The change also includes a cleanup in the header file by removing a redundant public access modifier.

Author: eclipse0922

cpp/open3d/pipelines/registration/SymmetricICP.cpp

@@ -54,7 +54,7 @@ Eigen::Matrix4d TransformationEstimationSymmetric::ComputeTransformation(
                 const Eigen::Vector3d &vt = target.points_[corres[i][1]];
                 const Eigen::Vector3d &ns = source.normals_[corres[i][0]];
                 const Eigen::Vector3d &nt = target.normals_[corres[i][1]];
-                Eigen::Vector3d d = vs - vt;
+                const Eigen::Vector3d d = vs - vt;
 
                 J_r.resize(2);
                 r.resize(2);

cpp/open3d/pipelines/registration/SymmetricICP.h

@@ -52,7 +52,6 @@ class TransformationEstimationSymmetric : public TransformationEstimation {
             const geometry::PointCloud &target,
             double max_correspondence_distance) const override;
 
-public:
     /// shared_ptr to an Abstract RobustKernel that could mutate at runtime.
     std::shared_ptr<RobustKernel> kernel_ = std::make_shared<L2Loss>();
 

cpp/tests/pipelines/registration/SymmetricICP.cpp

@@ -30,7 +30,6 @@ TEST(SymmetricICP, TransformationEstimationSymmetricComputeRMSE) {
     geometry::PointCloud source;
     geometry::PointCloud target;
 
-    // Create simple test point clouds with normals
     source.points_ = {{0, 0, 0}, {1, 0, 0}, {0, 1, 0}};
     source.normals_ = {{0, 0, 1}, {0, 0, 1}, {0, 0, 1}};
 
@@ -60,7 +59,6 @@ TEST(SymmetricICP, TransformationEstimationSymmetricComputeRMSENoNormals) {
 
     source.points_ = {{0, 0, 0}, {1, 0, 0}};
     target.points_ = {{0.1, 0.1, 0.1}, {1.1, 0.1, 0.1}};
-    // No normals
 
     registration::CorrespondenceSet corres = {{0, 0}, {1, 1}};
     registration::TransformationEstimationSymmetric estimation;