Rectified Flow

Straighten the probability flow ODE trajectories through a reflow procedure, enabling high-quality generation in very few (2-10) sampling steps. Rectified flow is a two-step process. First, train a flow matching model on the standard linear interpolation paths. Second, use the learned model to generate new data-noise pairs and train a new model to match the straighter trajectories implied by the first model. This “reflow” procedure straightens the ODE paths, allowing coarse numerical solvers (2-10 steps) to produce high-quality samples. Multiple reflow rounds can be applied.