We present SLAIM - Simultaneous Localization and Implicit Mapping. We propose
a novel coarse-to-fine tracking model tailored for Neural Radiance Field SLAM
(NeRF-SLAM) to achieve state-of-the-art tracking performance. Notably, existing
NeRF-SLAM systems consistently exhibit inferior tracking performance compared
to traditional SLAM algorithms. NeRF-SLAM methods solve camera tracking via
image alignment and photometric bundle-adjustment. Such optimization processes
are difficult to optimize due to the narrow basin of attraction of the
optimization loss in image space (local minima) and the lack of initial
correspondences. We mitigate these limitations by implementing a Gaussian
pyramid filter on top of NeRF, facilitating a coarse-to-fine tracking
optimization strategy. Furthermore, NeRF systems encounter challenges in
converging to the right geometry with limited input views. While prior
approaches use a Signed-Distance Function (SDF)-based NeRF and directly
supervise SDF values by approximating ground truth SDF through depth
measurements, this often results in suboptimal geometry. In contrast, our
method employs a volume density representation and introduces a novel KL
regularizer on the ray termination distribution, constraining scene geometry to
consist of empty space and opaque surfaces. Our solution implements both local
and global bundle-adjustment to produce a robust (coarse-to-fine) and accurate
(KL regularizer) SLAM solution. We conduct experiments on multiple datasets
(ScanNet, TUM, Replica) showing state-of-the-art results in tracking and in
reconstruction accuracy.

我们提出了 SLAIM - 同时定位和隐式建图。我们在神经光度场 SLAM（NeRF-SLAM）中提出了一种新颖的粗到细的跟踪模型，以实现最先进的跟踪性能。通过在 NeRF 之上实施高斯金字塔滤波器来解决 NeRF 系统在有限的输入视图情况下收敛到正确几何形状的挑战。我们的方法实现了局部和全局束调整，以产生强大（粗到细）和准确（KL 正则化器）的 SLAM 解决方案。在多个数据集（ScanNet，TUM，Replica）上进行实验证明在跟踪和重建准确性方面达到了最先进的结果。

SLAIM：鲁棒稠密神经 SLAM 用于在线跟踪和建图

SLAIM: Robust Dense Neural SLAM for Online Tracking and Mapping

The opacity of rigid 3D scenes with opaque surfaces is considered to be of a
binary type. However, we observed that this property is not followed by the
existing RGB-only NeRF-SLAM. Therefore, we are motivated to introduce this
prior into the RGB-only NeRF-SLAM pipeline. Unfortunately, the optimization
through the volumetric rendering function does not facilitate easy integration
of the desired prior. Instead, we observed that the opacity of ternary-type
(TT) is well supported. In this work, we study why ternary-type opacity is
well-suited and desired for the task at hand. In particular, we provide
theoretical insights into the process of jointly optimizing radiance and
opacity through the volumetric rendering process. Through exhaustive
experiments on benchmark datasets, we validate our claim and provide insights
into the optimization process, which we believe will unleash the potential of
RGB-only NeRF-SLAM. To foster this line of research, we also propose a simple
yet novel visual odometry scheme that uses a hybrid combination of volumetric
and warping-based image renderings. More specifically, the proposed hybrid
odometry (HO) additionally uses image warping-based coarse odometry, leading up
to an order of magnitude final speed-up. Furthermore, we show that the proposed
TT and HO well complement each other, offering state-of-the-art results on
benchmark datasets in terms of both speed and accuracy.

通过优化体积渲染过程中的光辐射度和不透明度，研究了刚性三维场景的不透明度类型以及如何将三态不透明度与混合参考位姿图优化相结合，以提高传统 RGB-only NeRF-SLAM 的速度和准确性。