# UFO-4D: Unposed Feedforward 4D reconstruction from Two Images

ICLR 2026

### 4D Interpolation

Here we demonstrate 4D interpolation results across different degrees of camera motion or object motion. Given the set of dynamic 3D Gaussians from our method, we rasterize image, depth, and motion at interpolated time and view. Depth and motion are defined at the canonical camera's coordinate. Only moving objects present non-white colors in our motion visualization.

#### Small/medium motion

Our model successfully interpolates images, depth, and motion, rendering high-quality outputs from predicted dynamic 3D Gaussians.
Input pairs
4D Interpolated image
Interpolated depth
Interpolated motion

#### Large motion

Even on scenarios with large object motion and camera motion, our model robustly outputs all estimates from unposed two images.
Input pairs
4D Interpolated image
Interpolated depth
Interpolated motion

#### Extreme motion

In highly challenging cases (such as minial image overlaps or extremely large motion), our model struggles to accurately determine the motion of moving objects. However, camera motion estimation and geometry for static region remains still very robust. The red color in the depth map denotes disocclusion where no image evidence is provided.
Input pairs
4D Interpolated image
Interpolated depth
Interpolated motion

### Qualitative comparison

We compare our method against direct competitors, DynaDUSt3R, ZeroMSF, and St4RTrack, and visualize predicted depth and projected optical flow on Stereo4D, Bonn, and KITTI dataset. Our method outperforms competing approaches by estimating more accurate depth and motion, even under challenging conditions such as significant camera rotation and large object motion. It effectively disentangles dynamic object motion from camera ego-motion, preserving sharp boundaries and geometric consistency.

#### Stereo4D dataset

Input Pair
DynaDUSt3R
ZeroMSF
St4RTrack
UFO-4D (Ours)
Ground truth

#### Bonn dataset

Input Pair
DynaDUSt3R
ZeroMSF
St4RTrack
UFO-4D (Ours)
Ground truth

#### KITTI dataset

Input Pair
DynaDUSt3R
ZeroMSF
St4RTrack
UFO-4D (Ours)
Ground truth