Flow Where You Want

This tutorial serves as an intuitive introduction to adding inference-time controls to pretrained flow matching and rectified flow generative models, to make them perform tasks they weren't trained to do. We take an unconditional flow model trained on MNIST digits and apply two types of guidance: classifier guidance to generate specific digits, and inpainting to fill in missing pixels. Both approaches work by adding velocity corrections during the sampling process to steer the model toward desired outcomes. Since modern generative models operate in compressed latent spaces, we examine guidance methods that work directly in latent space as well as those that decode to pixel space. We also explore PnP-Flow, which satisfies constraints by iteratively projecting samples backward and forward in time rather than correcting flow velocities. The approaches demonstrated here work with other flow models and control tasks, so you can guide flows where you want them to go.