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LT-Mem: Volatility-Aware Spatio-Temporal Memory for Lifelong Scene Understanding

LT-Mem: Volatility-Aware Spatio-Temporal Memory for Lifelong Scene Understanding

DGIST team, accepted to IROS 2026. Robots operating long-term revisit evolving environments; existing systems either overwrite history to keep an up-to-date map or store semantic snapshots without cross-session object identity — the authors call this temporal amnesia: unable to answer "Where has the green chair been across all sessions?" LT-Mem is a three-layer solution: (1) Perception: MASt3R-SLAM multi-session alignment (Sim(3) anchors + inter-session loop closures + joint g2o optimization) plus SAM3 instance segmentation extracting per-object centroid/volume/visual embedding; (2) Reasoning: five evidence scores (E1 spatial proximity, E2 temporal continuity, E3 feature similarity as the primary signal w=0.45, E4 motion consistency, E5 occlusion handling) drive deterministic cross-session re-identification, with a constrained LLM judge only for ambiguous cases (MATCH/NEW-TRACK/HOLD); a structural integrity check triggers a session-wide HOLD on alignment failure; a volatility score V accumulates evidence in a Bayesian manner (Eq.2, one-time LLM prior), selecting among OVERWRITE/HOLD/MULTI-HYPOTHESIS updates; (3) Tri-Memory: Live stores current states, Delta logs timestamped events (APPEAR/DISAPPEAR/MOVE/RE-APPEAR/NONE), Meta accumulates volatility statistics feeding back into the update policy. The paper releases LT-VQA (two indoor envs, 10 objects × 10 sessions each, plus an outdoor parking lot over 10 sessions; 61 state-change events and 80 QA pairs). Results: Event F1 0.910 / QA-Event 0.820 / QA-Freq 0.600, beating Geometric/Text-Batch/VLM-Batch/STAR baselines across the board, with 438K tokens — 1/16 of VLM-Batch (7,114K) and 1/100 of STAR (45,859K); swapping in Qwen2.5-3B still reaches 0.885, showing the gains come from the structured memory architecture rather than LLM capacity. Ablations: removing re-identification collapses F1 to 0.140; removing volatility-awareness drops it to 0.615. Scene-level statistics on the parking lot even answer "when should I go to find a parking spot" (8:00 AM, 0 cars vs 1:03 PM, 34 cars).

Yumin Lee, Hyoseok Ju, Giseop Kim · 415 views · Aug 19, 2026
SLAMLong-Term-AutonomyScene UnderstandingAug 19, 2026
DL-SLAM: Enabling High-Fidelity Gaussian Splatting SLAM in Dynamic Environments based on Dual-Level Probability

DL-SLAM: Enabling High-Fidelity Gaussian Splatting SLAM in Dynamic Environments based on Dual-Level Probability

Recent advances in 3D Gaussian Splatting (3DGS) have enabled significant progress in dense dynamic Simultaneous Localization And Mapping (SLAM). Prevailing methods typically discard predefined dynamic objects, ignoring that transiently static objects offer valuable geometric constraints for pose estimation. A recent work attempts to leverage this potential by employing per-pixel uncertainty maps to quantify the magnitude of motion. While this approach enables transiently static objects to enhance pose estimation, it erroneously integrates these objects into the static map, resulting in persistent artifacts. Moreover, its reliance on purely geometric information leads to ambiguous object boundaries in the uncertainty maps. To overcome these limitations, we present DL-SLAM, a monocular Gaussian Splatting SLAM system built upon a novel dual-level probabilistic framework. Our method computes dynamic probability maps by combining semantic and geometric information. These pixel-level probabilities are lifted to 3D and aggregated to derive an object-level dynamic probability for each instance. Object-level probability enables the categorical pruning of dynamic Gaussians, resulting in an artifact-free static map. The static map, in turn, provides a geometrically consistent guidance to refine the pixel-wise probabilities, enhancing their reliability. Experimental results demonstrate that DL-SLAM outperforms existing approaches, improving tracking accuracy by up to 13% while generating high-fidelity semantic maps.

Ziheng Xu, Qingfeng Li, Xuefeng Liu · 622 views · Jul 2, 2026
Dynamic EnvironmentSLAM3D Gaussian SplattingJul 2, 2026

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