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arXiv · 2608.00094

Video Models as Native 4D Renderers: World-Grounded Conditioning from Animated Mesh

Junhao Chen·Mingjin Chen·Henghaofan Zhang·Minglin Chen·Liaoyuan Fan·Boran Zhang·Saining Zhang·Mingze Sun·Hao Zhao·Ruqi Huang·Zhihao Li·Yufei Wang
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Abstract

Pretrained video diffusion models can act as renderers when the desired scene state is already specified by an animated mesh, a camera trajectory, and a reference image. This 4D generative rendering setting raises a representation question: what image-format condition lets a video backbone obey both camera motion and scene-internal animation? We propose DAR, a reference-guided renderer that extends Wan2.2 camera control from Pl\"ucker rays alone to a joint camera-plus-geometry interface. DAR projects a neural 4D G-buffer (tracking, world position, and normal) from the animated mesh and injects it through a widened control adapter while preserving the pretrained image-to-video prior. The central design choice is the pair of tracking and world position. Tracking identifies the persistent surface element that should carry appearance; world position gives its current scene-coordinate state; normal supplies local shape. Depth plus calibrated rays can recover 3D in principle, but depth is a camera-dependent chart in which camera and object motion are mixed. On the 68-case DAR-4D benchmark, LoRA DAR reaches PSNR 23.22, SSIM 0.895, and LPIPS 0.134, improving over off-the-shelf Wan2.2-Depth by 1.54 dB PSNR; a full fine-tune reaches PSNR 25.36 and SSIM 0.917. Matched ablations show that replacing world position by depth reduces PSNR by 1.26--1.55 dB at every checkpoint, supporting tracking+world-position correspondence as a practical 4D rendering condition.

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Junhao Chen, Mingjin Chen, Henghaofan Zhang, Minglin Chen, Liaoyuan Fan, Boran Zhang, Saining Zhang, Mingze Sun, Hao Zhao, Ruqi Huang, Zhihao Li, Yufei Wang. 2026-07-30. Video Models as Native 4D Renderers: World-Grounded Conditioning from Animated Mesh. https://arxiv.org/abs/2608.00094

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