ZipMap: Linear-Time Stateful 3D Reconstruction via Test-Time Training

Technical Analysis is a stateful feed-forward model that achieves linear-time, bidirectional 3D reconstruction while matching or surpassing the accuracy of quadratic time methods. High-level Analogy: Imagine you're watching a very long documentary about a new city, and you want to create a perfect 3D model of that city. The Old Way (Slow & Detailed): The best existing methods (like VGGT or π3) are like having to re-watch the entire documentary from start to finish every single time you want to add a new building or detail to your 3D model. If the documentary gets longer, this re-watching process becomes incredibly, prohibitively slow – for a movie twice as long, it takes four times as much effort! Another Old Way (Fast & Less Detailed): Other methods (like CUT3R or TTT3R) try to be faster by only focusing on short segments of the documentary at a time, building up the city model piece by piece. But because they don't look at the whole picture efficiently, they might miss crucial connections between distant scenes, leading to a less accurate or complete 3D model. ZipMap's Way: ZipMap is like having a super-smart 'memory assistant' that watches the entire documentary once. As it watches, it continuously and very efficiently compresses all the essential information about the city into a single, compact, dynamic 'city guide' or 'cheat sheet' in its memory. This guide isn't just a simple summary; it's a sophisticated, adaptable knowledge base. Now, when you want to add a new…