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iMAP: Implicit Mapping and Positioning in Real-Time (2103.12352v2)

Published 23 Mar 2021 in cs.CV

Abstract: We show for the first time that a multilayer perceptron (MLP) can serve as the only scene representation in a real-time SLAM system for a handheld RGB-D camera. Our network is trained in live operation without prior data, building a dense, scene-specific implicit 3D model of occupancy and colour which is also immediately used for tracking. Achieving real-time SLAM via continual training of a neural network against a live image stream requires significant innovation. Our iMAP algorithm uses a keyframe structure and multi-processing computation flow, with dynamic information-guided pixel sampling for speed, with tracking at 10 Hz and global map updating at 2 Hz. The advantages of an implicit MLP over standard dense SLAM techniques include efficient geometry representation with automatic detail control and smooth, plausible filling-in of unobserved regions such as the back surfaces of objects.

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Authors (4)
  1. Edgar Sucar (11 papers)
  2. Shikun Liu (21 papers)
  3. Joseph Ortiz (15 papers)
  4. Andrew J. Davison (64 papers)
Citations (520)

Summary

  • The paper presents iMAP’s main contribution: a unified neural representation that performs simultaneous tracking and mapping in real time.
  • It employs a continual learning paradigm with active sampling and differentiable rendering to incrementally refine 3D scene reconstructions.
  • The approach achieves notable memory compression by reducing room-scale scenes to approximately 1MB while maintaining robust mapping from a single viewpoint.

Overview of iMAP: Implicit Mapping and Positioning in Real-Time

The paper introduces iMAP, a novel approach in the domain of Simultaneous Localization and Mapping (SLAM), challenging existing methodologies through its use of a single neural network for scene representation. Unlike traditional systems that often rely on pre-captured datasets or extensive pre-training, iMAP incrementally trains an implicit 3D representation from scratch, dynamically constructing a room-scale scene from a single viewpoint. This adaptability avoids the necessity for prior training data, granting significant flexibility and robustness in diverse environments.

Key Contributions

  • Unified Representation: iMAP uses a singular neural representation, integrating both tracking and mapping functionalities. This is contrary to traditional NeRF-like systems requiring prolonged training periods, thereby achieving real-time performance.
  • Continual Learning: The system efficiently implements a continual learning paradigm through a 'Parallel Tracking and Mapping' architecture and active sampling-based optimization, employing differentiable rendering to refine scene reconstruction.
  • Compression Capability: The memory efficiency of iMAP is noteworthy, achieving compression rates much higher than traditional voxel hashing methods, reducing room-scale scenes to approximately 1MB.

Strengths and Limitations

The paper presents both quantitative and qualitative data supporting iMAP's effectiveness in producing smooth and complete reconstructions. However, it acknowledges a limitation in accurately representing fine details compared to traditional methods that utilize TSDF fusion or voxel hashing.

iMAP demonstrates a strong intrinsic ability to fill unobserved regions without relying on explicit priors or datasets, showcasing the utility of the inductive biases present in its MLP-based architecture. This implicit neural representation can represent complex scenes using minimal data input, although further refinement is necessary to improve detail accuracy.

Implications and Future Research

iMAP's introduction marks a significant shift in SLAM systems toward utilizing implicit neural networks for real-time scene understanding and representation. As systems like iMAP evolve, they have the potential to enable new applications, such as joint semantic encoding, within a single representation framework. This could streamline processes in robotics and autonomous systems, where real-time and adaptive scene interpretation are critical.

Future research directions may focus on improving scalability and performance across larger environments. Specifically, exploring different keyframe management strategies, sub-mapping techniques, or alternative continual learning approaches would help enhance the system's adaptability and efficiency. Additionally, as architectural advancements occur, there could be opportunities to leverage self-similarities for more sophisticated implicit completions.

In conclusion, iMAP sets a foundational step towards real-time implicit neural SLAM systems, opening avenues for further inquiries into memory-efficient, adaptable, and self-optimizing scene representations. This represents a promising frontier for both theoretical exploration and practical application within the field of real-time computer vision and robotics.