mola_metric_maps

Advanced metric map classes, using the generic mrpt::maps::CMetricMap interface, for use in other MOLA odometry and SLAM modules.

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README

mola_metric_maps

Advanced metric map classes for LiDAR odometry and SLAM, built on the generic mrpt::maps::CMetricMap interface. All maps are serializable, visualizable, and integrate with the mp2p_icp registration library.

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Map classes

Production-quality maps

Class	Header	Description
mola::HashedVoxelPointCloud	HashedVoxelPointCloud.h	Flat sparse hash map of cubic voxels. Up to 32 points per voxel stored without heap allocation (fixed array SSO). Backend: tsl::robin_map. Implements NearestNeighborsCapable.
mola::SparseVoxelPointCloud	SparseVoxelPointCloud.h	Two-level voxel map: sparse outer blocks + 32³ inner FixedDenseGrid3D. Tracks per-voxel point means; supports voxel-mean ICP matching. Implements NearestNeighborsCapable. The primary workhorse map in MOLA LO/SLAM.
mola::NDT	NDT.h	Normal Distributions Transform map (Magnusson 2007). Fits a Gaussian per voxel; planar voxels expose NearestPlaneCapable, non-planar ones expose NearestNeighborsCapable. Enables automatic point-to-point vs. point-to-plane pairing selection.
mola::KeyframePointCloudMap	KeyframePointCloudMap.h	Keyframe-based map: each keyframe holds a local point cloud plus a SE(3) pose. Supports map corrections without re-inserting points (just update poses). Implements IcpPrepareCapable, NearestPointWithCovCapable, MetricMapMergeCapable, and KeyframeMapCapable.

Experimental / work-in-progress maps

Class	Header	Status
mola::SparseTreesPointCloud	SparseTreesPointCloud.h	Coarse 3D grid of independent CSimplePointsMap sub-maps, each with its own KD-tree. Functionally complete but not benchmarked against the hash-based alternatives for typical SLAM workloads.
mola::OccGrid	OccGrid.h	Wraps mrpt::maps::COccupancyGridMap2D with a super-resolution likelihood cache. The cache infrastructure is in place but likelihood population is not yet implemented (// TODO). Not used in any production pipeline.

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Utility / internal classes

Class	Header	Description
mola::index3d_t<T>	index3d_t.h	Discrete 3D integer index. Works as key in std::map and std::unordered_map / tsl::robin_map via the index3d_hash functor, which implements the Teschner et al. (2003) spatial hash.
mola::FixedDenseGrid3D<T,N,C>	FixedDenseGrid3D.h	Dense NxNxN grid (N=2^SIDE_NUM_BITS) allocated with calloc for fast zero-init. Used as the inner block in SparseVoxelPointCloud. Requires trivially-copyable cell types.

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Build and install

Refer to the root MOLA repository.

License

Copyright (C) 2018-2026 Jose Luis Blanco jlblanco@ual.es, University of Almeria

This package is released under the GNU GPL v3 license as open source for research and evaluation purposes only. Commercial licenses available upon request, for this package alone or in combination with the complete SLAM system.