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MoFlow: One-Step Flow Matching for Human Trajectory Forecasting via Implicit Maximum Likelihood Estimation based Distillation
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Proposes MoFlow, a conditional flow matching model that jointly predicts K correlated trajectory sets for all agents, and distills it into a one-step student via IMLE using only teacher samples.
Problem
Human trajectory forecasting must capture multi-modal future motion, but diffusion/flow samplers are slow and independently drawn samples lack diversity across agents' futures.
Approach
A flow model with a closest-prediction regression plus classification loss that yields K correlated trajectory hypotheses, distilled into a one-step generator by conditional IMLE with Chamfer distance, requiring only teacher samples rather than consistency-style training.
Key results
- On NBA, MoFlow-IMLE reaches 0.71 minADE20 / 0.87 minFDE20 over 4.0s, versus 0.81/1.16 for LED, per the paper's table.
- On SDD, MoFlow achieves 7.50 minADE20 vs. 7.76 for TUTR (prior best ADE), with FDE 11.96 close to the best of 11.09.
- The one-step IMLE student is reported as 100 times faster than the 100-step teacher ODE sampler while keeping performance largely unchanged.
- GAN-based distillation baselines (WGAN, DCGAN) reach 1.78/2.90 and 1.71/2.98 on NBA, far worse than IMLE distillation.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| Use MoFlow instead of LED* | NBA trajectory forecasting · NBA, Total (4.0s) | min20ADE: 0.81 -> 0.71 | Helped |
| Use MoFlow instead of LED* | NBA trajectory forecasting · NBA, Total (4.0s) | min20FDE: 1.16 -> 0.87 | Helped |
| Distill MoFlow with IMLE for one-step sampling | MoFlow · NBA, Total (4.0s) | min20ADE: 0.71 -> 0.71 | No clear effect |
| Distill MoFlow with IMLE for one-step sampling | MoFlow · NBA, Total (4.0s) | min20FDE: 0.87 -> 0.86 | No clear effect |
| Distill MoFlow with IMLE for one-step sampling | MoFlow · ETH-UCY | min20ADE: 0.20 -> 0.21 | No clear effect |
| Distill MoFlow with IMLE for one-step sampling | MoFlow · ETH-UCY | min20FDE: 0.32 -> 0.33 | No clear effect |
| Distill MoFlow with IMLE for one-step sampling | MoFlow · SDD | min20ADE: 7.50 -> 7.85 | Hurt |
| Distill MoFlow with IMLE for one-step sampling | MoFlow · SDD | min20FDE: 11.96 -> 12.86 | Hurt |
| Replace IMLE distillation with WGAN (ablation) | MoFlow · NBA | min20ADE: 0.71 -> 1.78 | Hurt |
| Replace IMLE distillation with WGAN (ablation) | MoFlow · NBA | min20FDE: 0.87 -> 2.90 | Hurt |
| Replace IMLE distillation with DCGAN (ablation) | MoFlow · NBA | min20ADE: 0.71 -> 1.71 | Hurt |
| Replace IMLE distillation with DCGAN (ablation) | MoFlow · NBA | min20FDE: 0.87 -> 2.98 | Hurt |
Surprising findings
- On SDD, the IMLE student (7.85/12.86) is somewhat worse than the teacher MoFlow (7.50/11.96), so distillation is not entirely lossless there.
- On ETH-UCY, the proposed method is only comparable to the best existing models rather than clearly superior, since the benchmark has plateaued.
Limitations
- ETH-UCY results are only on par with the best baselines, and SDD FDE trails the best model by about 0.5 pixels.
- Evaluation is limited to trajectory datasets with no scene map or semantic context in the current model.
Experimental setup
Datasets: SportVU NBA ETH-UCY Stanford Drone Dataset
Benchmarks: SportVU NBA ETH-UCY SDD
Metrics: minADE minFDE
Baselines: MemoNet NPSN GroupNet MID LED TUTR EqMotion EigenTraj SingularTraj WGAN DCGAN
Builds on: flow matching implicit maximum likelihood estimation LED Motion Indeterminacy Diffusion
Closest papers by meaning
- FlowMoP: Stochastic Multi-Person Motion Prediction (NeurIPS 2026 · similarity 0.89)
- Multi-modal Knowledge Distillation-based Human Trajectory Forecasting (CVPR 2025 · similarity 0.86)
- Physical Plausibility-aware Trajectory Prediction via Locomotion Embodiment (CVPR 2025 · similarity 0.85)
- SingularTrajectory: Universal Trajectory Predictor Using Diffusion Model (CVPR 2024 · similarity 0.85)
- MolmoMotion: Forecasting Point Trajectories in 3D with Language Instruction (NeurIPS 2026 · similarity 0.85)
- GoalFlow: Goal-Driven Flow Matching for Multimodal Trajectories Generation in End-to-End Autonomous Driving (CVPR 2025 · similarity 0.85)
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