Dense Flow from Adaptive Correspondence

원문 초록

Optical flow requires reliable matching from sufficient visual context and precise motion at every pixel. Existing methods such as WAFT match and estimate flow on the same coarse grids, then recover dense flow through learned upsampling, without explicitly linking visual support for matching to dense flow reconstruction. Our key insight is that dense pixel-level flow does not require equally dense matching. We decouple correspondence scale from flow resolution by adapting the size and shape of spatial supports to image structure for reliable matching, while reusing these supports for precise dense flow reconstruction. We realize this in Flow from Adaptive Token Estimation (FATE), whose token supports expand within coherent regions and contract near motion boundaries. Shared pixel-to-token associations pool features for matching and reconstruct pixel flow from token motions. Flow supervision jointly trains pixel grouping, token matching, and flow estimation without grouping labels, allowing FATE to anticipate which pixels are likely to move together from appearance alone. Trained on FlyingChairs/FlyingThings3D, FATE achieves the highest zero-shot accuracy on Sintel Final and KITTI, a critical setting given scarce real-world flow labels. For visible pixels, FATE improves accuracy within coherent regions, and more near motion boundaries. Its largest gains occur where direct matches are unavailable: Occluded or out-of-frame pixels account for roughly 10% of valid pixels but 50% of WAFT's total error. Experiments show that adaptive correspondence through pixel-to-token grouping enables reliable matching and precise pixel-level flow, improving generalization to unseen real scenes.