As video world models become increasingly powerful, do we still need explicit 3D? A commonly misunderstood point is this: video world models are not “just 2D.” Their ability to maintain multi-view consistency, temporal stability, and realistic interaction necessarily implies that their latent knowledge encodes 3D world structure. Without some notion of 3D, consistency itself would not be possible. The real distinction, therefore, is not whether a model has 3D but whether that 3D exists implicitly or explicitly. Implicit 3D lives inside latent spaces and network weights. It supports generation, but it is difficult to localize, edit, constrain, or reason about. It allows the world to exist, but not to be used. Explicit 3D, in contrast, exists as structure and state: it is addressable, editable, composable, and transferable. Its purpose is not better visual fidelity, but operability to allow the world to be manipulated, controlled, and executed. From this perspective, video and 3D are not competing paradigms but a layered system: 2D/video is the interface to human perception; 3D is the interface to the physical world. They can reinforce each other, but neither forms a closed loop on its own. In practice, data not model architecture sets the upper bound of world models. Explicit 3D may not be the final user-facing representation, but it is likely the most effective pathway toward scalable, high-quality, and controllable data. Through explicit 3D/4D representations, worlds can be constructed systematically: interactions can be programmatically sampled, states and actions can be composed, rendered into images and videos, and fed back to train video world models. Seen this way, 3D is not the destination it is the starting point for scaling. What truly drives progress forward is never the model itself. Whether we capture the world or imagine new ones, whether data comes from observation or intent, whether we model what is or what should be the direction of the world is ultimately determined by human choice and purpose. Models may extend the world, but humans decide where it goes. #Genie3 #worldmodel