ByteDance's PICO-MR team has officially open-sourced **EX-4D**, a groundbreaking 4D video generation framework. This tool can generate high-quality, multi-view 4D video sequences (3D space + time dimension) from a single viewpoint (monocular) video, marking a new milestone in video generation technology. EX-4D not only surpasses existing open-source methods in technical metrics but also provides critical support for immersive 3D content creation and "world model" construction. Below is an in-depth analysis of this cutting-edge technology by AIbase.
**Technical Breakthrough: From Monocular Video to Free Perspective**
Traditional video generation technologies face two major challenges in multi-view generation: first, they require expensive multi-view cameras and datasets for training; second, they struggle with occluded areas, leading to object penetration or detail distortion in extreme views. EX-4D successfully solves these issues through its innovative **Depth-Enclosed Mesh (DW-Mesh)** representation and lightweight adaptation architecture.
DW-Mesh is the core technology of EX-4D. It constructs a fully enclosed mesh structure to record visible and hidden surfaces in the scene, enabling unified processing of complex scene topologies without multi-view supervision. Combined with a pre-trained depth prediction model, EX-4D projects single-frame pixels into 3D space to form mesh vertices and accurately marks occluded regions based on geometric relationships. This method ensures that generated videos maintain physical consistency and detail integrity even at extreme perspectives (such as ±90°).
Additionally, EX-4D introduces two simulated mask generation strategies—**rendering masks** and **tracking masks**—which simulate perspective movement and inter-frame consistency to solve the scarcity of multi-view training data. These strategies allow EX-4D to "imagine" full-view data based solely on monocular video, significantly reducing data collection costs.
**Performance: Comprehensive Leadership in Metrics**
EX-4D demonstrated outstanding performance in performance tests. Based on a dataset containing 150 network videos, EX-4D comprehensively surpassed existing open-source methods in industry-standard metrics such as **FID (Fréchet Inception Distance)**, **FVD (Fréchet Video Distance)**, and **VBench**. Especially in extreme view generation tasks (such as near 90°), EX-4D's performance advantages were particularly evident, with generated videos showing more realistic details and occlusion logic.
In a subjective evaluation involving 50 volunteers, 70.7% of participants believed that EX-4D outperformed other open-source methods in terms of physical consistency at extreme perspectives. This indicates that EX-4D not only leads in technical metrics but also receives high recognition from users in practical applications.
ByteDance has completely open-sourced EX-4D, with code and related documentation published on GitHub, providing free access for global developers. This move not only reflects ByteDance's contribution to the open-source community but also lays the foundation for innovative applications in fields such as immersive 3D movies, virtual reality (VR), and augmented reality (AR).
EX-4D is based on the pre-trained WAN-2.1 model, combined with a **LoRA-based Adapter** architecture, maintaining computational efficiency while incorporating geometric prior information from DW-Mesh to ensure geometric consistency and frame coherence in generated videos. This lightweight design allows EX-4D to run efficiently even in resource-constrained environments, suitable for a wide range of development scenarios.
EX-4D's release is considered an important advancement in building "world models." Compared to traditional one-way video generation models, EX-4D enables users to freely explore video content, similar to switching perspectives in a "parallel universe." This camera-controllable 4D generation technology opens up infinite possibilities for immersive content creation, such as interactive 3D movies, virtual tourism, and game development.
The head of ByteDance's PICO-MR team stated that EX-4D is the culmination of years of research by the team in 3D reconstruction and 4D scene generation. In the future, the team will continue to optimize model performance and explore broader application scenarios. AIbase believes that EX-4D's open source will accelerate the popularization of AI video generation technology and promote the implementation of multimodal AI in the creative industry.
Website: https://github.com/tau-yihouxiang/EX-4D