In Vision-and-Language Navigation (VLN), an agent is required to plan a path to the target specified by the language instruction, using its visual observations. Consequently, prevailing VLN methods primarily focus on building powerful planners through visual-textual alignment. However, these approaches often bypass the imperative of comprehensive scene understanding prior to planning, leaving the agent with insufficient perception or prediction capabilities. Thus, we propose P3Nav, a novel end-to-end framework integrating perception, prediction, and planning in a unified pipeline to strengthen the VLN agent's scene understanding and boost navigation success. Specifically, P3Nav augments perception by extracting complementary cues from object-level and map-level perspectives. Subsequently, our P3Nav predicts waypoints to model the agent's potential future states, endowing the agent with intrinsic awareness of candidate positions during navigation. Conditioned on these future waypoints, P3Nav further forecasts semantic map cues, enabling proactive planning and reducing the strict reliance on purely historical context. Integrating these perceptual and predictive cues, a holistic planning module finally carries out the VLN tasks. Extensive experiments demonstrate that our P3Nav achieves new state-of-the-art performance on the REVERIE, R2R-CE, and RxR-CE benchmarks.
Figures & tables
Figure 1: Motivation of our method. (a) Scene information, such as objects, maps, and waypoints are crucial for grounding instructions to visual observations. (b.1) Early models are of a “planning-only” structure, with limited scene understanding due to implicit feature extraction and aggregation. (b.2) Recent methods build external perception/prediction modules, but suffer from information loss and error accumulation. (b.3) Our method unifies perception, prediction, and planning in a single network, through a unified environment representation with end-to-end feature propagation between each stage.
Figure 2: Pipeline of our P 3 Nav model. The agent first encodes its discrete observations into a BEV representation, upon which two perception decoders output object and map features, in parallel. Subsequently, two predictors sequentially decode waypoint cues and future scene semantics. Ultimately, a planning decoder incorporates the features from all the preceding modules to produce a comprehensive navigation decision.
Figure 3: Ground truth map semantics generation. First, we crop nearby regions from the point clouds with semantic annotations in the Matterport3D [ 8 ] dataset, and project them onto a plane. Second, we generate a template-based description of the map. Then we prompt the VLM to refine the description. The last token from the last VLM decoder layer is defined as the ground truth map semantics.
Figure 4: Pipeline of waypoint-level prediction. (a) Waypoint feature is decoded via the multi-attention deformable transformer decoder; after that, a heatmap is generated through up-sampling. (b) NMS and depth-based post-processing are performed to identify candidate waypoints, addressing the discrete-to-continuous transfer problem.
Validation Unseen
Test Unseen
Methods
SR ↑
SPL ↑
RGS ↑
RGSPL ↑
SR ↑
SPL ↑
RGS ↑
RGSPL ↑
HAMT [ 11 ]
32.95
30.20
18.92
17.28
30.40
26.67
14.88
13.08
DUET [ 12 ]
46.98
33.73
32.15
23.03
52.51
36.06
31.88
22.06
DSRG [ 60 ]
47.83
34.02
32.69
23.37
54.04
37.09
32.49
22.18
GridMM [ 66 ]
51.37
36.47
34.57
24.56
53.13
36.60
34.87
23.45
BEVBert [ 1 ]
51.78
36.37
34.71
24.44
52.81
36.41
32.06
22.09
Table 1: Comparison with SOTA methods on REVERIE dataset [ 45 ] . The best and second-best results are marked as bold and underline , respectively.
R2R-CE
RxR-CE
Methods
NE ↓
OSR ↑
SR ↑
SPL ↑
NE ↓
SR ↑
SPL ↑
nDTW ↑
SDTW ↑
CMA [ 19 ]
6.20
52
41
36
8.76
26.50
22.12
47.03
23.74
VLN ↻ BERT [ 19 ]
5.74
53
44
39
8.98
27.08
22.66
46.71
24.79
Reborn [ 3 ]
5.40
57
50
46
5.98
48.60
42.05
63.35
41.82
ETPNav [ 2 ]
4.71
65
57
49
5.64
54.79
44.89
61.90
45.33
BEVBert [ 1 ]
4.57
67
59
50
5.54
55.47
45.32
62.45
46.01
Table 2: Comparison with SOTA methods on Validation Unseen splits of R2R-CE [ 28 ] and RxR-CE [ 3 ] datasets. The best and second-best results are marked as bold and underline , respectively.
Figure 5: Analysis of (a) object-level perception (mAP and mAR at IoU=0.5) and (b) waypoint-level prediction. BTG denotes [ 19 ] , with BTG-B and BTG-U indicating its baseline version and U-Net [ 49 ] variants, respectively.
Figure 6: Case study in the simulator. (a) Comparison of navigation results: BEVBert [ 1 ] (left) fails to find the target, while our P 3 Nav (right) leverages perception and prediction information for accurate waypoint selection. (b) Visualization of object-level perception.
Figure 7: Case study in the real world. (a) Visualization of the path from the third-person view. (b) The robot’s first-person observations during navigation.
REVERIE
R2R-CE
RxR-CE
Model Configs
SR ↑
SPL ↑
SR ↑
SPL ↑
SR ↑
SPL ↑
nDTW ↑
SDTW ↑
Base Model
50.96
36.02
59.02
50.07
55.46
45.32
62.45
45.99
w/o Object Decoder
54.13
36.58
61.79
51.89
57.45
46.67
63.38
47.53
w/o Map Decoder
53.85
36.53
60.83
50.94
56.89
46.45
63.41
47.46
w/o Waypoint Decoder
55.04
36.67
61.87
52.09
57.47
47.71
63.78
47.85
w/o Scene Decoder
53.68
36.17
61.22
51.45
57.14
47.10
62.98
47.06
Table 3: Ablation study of intermediate modules. When ablating the waypoint decoder, we employ an external waypoint predictor [ 19 ] for R2R-CE [ 28 ] and RxR-CE [ 3 ] .
REVERIE
R2R-CE
RxR-CE
Scale
SR ↑
SPL ↑
SR ↑
SPL ↑
SR ↑
SPL ↑
nDTW ↑
SDTW ↑
11 × 11
54.91
36.52
61.78
51.99
57.61
47.81
63.97
47.85
15 × 15
55.98
36.78
62.17
52.32
58.01
47.92
64.29
48.04
21 × 21
55.73
36.69
62.01
52.18
57.95
47.88
64.22
47.99
Table 4: Comparison of different BEV scales. Odd scales are adopted to guarantee that the agent resides in the center cell, with the cell size fixed at 0.5 m.
REVERIE
R2R-CE
RxR-CE
Design
SR ↑
SPL ↑
SR ↑
SPL ↑
SR ↑
SPL ↑
nDTW ↑
SDTW ↑
Modular
54.15
36.29
61.73
51.81
57.42
47.57
63.59
47.90
End-to-End
55.98
36.78
62.17
52.32
58.01
47.92
64.29
48.04
Table 5: Comparison of modular and end-to-end designs for integrating perception and prediction intermediate modules in the navigation pipeline.
REVERIE
R2R-CE
RxR-CE
Methods
SR ↑
SPL ↑
SR ↑
SPL ↑
SR ↑
SPL ↑
nDTW ↑
SDTW ↑
Vm
53.82
36.51
61.32
51.44
57.02
47.13
63.53
47.66
T
54.46
36.59
61.41
51.56
57.21
47.25
63.60
47.72
Ve
55.43
36.70
61.96
52.02
57.88
47.79
64.11
47.89
Vi
55.98
36.78
62.17
52.32
58.01
47.92
64.29
48.04
Table 6: Comparison of different ground truth generation methods for map semantics.
Appendix figures & tables6 assets
Supplementary material from the paper’s appendix.
Appendix
Figure 8: Pipeline of our planning module. Immediate scene grounding evaluates local perceptual feasibility using BEV features and scene semantics. Prospective future evaluation reasons over candidate waypoint graphs to estimate future consistency with the instruction. Global memory correction incorporates historical information through a global graph representation. The resulting scores are progressively integrated through two fusion layers to produce the final navigation score.
R2R
RxR
Methods
NE ↓
SR ↑
SPL ↑
SR ↑
nDTW ↑
SDTW ↑
HAMT [ 11 ]
3.65
66
61
56.5
63.1
48.3
HOP [ 47 ]
3.80
64
57
42.3
52.0
33.0
HOP+ [ 48 ]
3.49
67
61
45.7
52.0
36.0
EnvEdit [ 30 ]
3.24
69
64
62.8
68.5
54.6
BEVBert [ 1 ]
2.81
75
64
68.5
69.6
58.6
Appendix
Table 7: Comparison with SOTA methods on Validation Unseen splits of R2R [ 4 ] and RxR [ 29 ] datasets. The best and second-best results are marked as bold and underline , respectively.
Figure 9: First case study in the simulation. The image sequence shows the robot’s panoramic observations during navigation.
Figure 10: Second case study in the simulation. The image sequence shows the robot’s panoramic observations during navigation.
Figure 11: First case study in the real world. (a) Visualization of the path from the third-person view. (b) The robot’s first-person observations during navigation.
Figure 12: Second case study in the real world. (a) Visualization of the path from the third-person view. (b) The robot’s first-person observations during navigation.