4Real-Video-V2: Fused View-Time Attention and Feedforward Reconstruction
  for 4D Scene Generation
Authors: name: Chaoyang Wang, name: Ashkan Mirzaei, name: Vidit Goel, name: Willi Menapace, name: Aliaksandr Siarohin, name: Avalon Vinella, name: Michael Vasilkovsky, name: Ivan Skorokhodov, name: Vladislav Shakhrai, name: Sergey Korolev, name: Sergey Tulyakov, name: Peter Wonka

We propose the first framework capable of computing a 4D spatio-temporal grid
of video frames and 3D Gaussian particles for each time step using a
feed-forward architecture. Our architecture has two main components, a 4D video
model and a 4D reconstruction model. In the first part, we analyze current 4D
video diffusion architectures that perform spatial and temporal attention
either sequentially or in parallel within a two-stream design. We highlight the
limitations of existing approaches and introduce a novel fused architecture
that performs spatial and temporal attention within a single layer. The key to
our method is a sparse attention pattern, where tokens attend to others in the
same frame, at the same timestamp, or from the same viewpoint. In the second
part, we extend existing 3D reconstruction algorithms by introducing a Gaussian
head, a camera token replacement algorithm, and additional dynamic layers and
training. Overall, we establish a new state of the art for 4D generation,
improving both visual quality and reconstruction capability.