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Foundation Lab

Flow Matching & Rectified Flows

Simpler than diffusion: no noise schedule to tune

Concept 83 of 100Generative ModelsPhase 4
#83Flow MatchGenerative Models
key equation\frac{dx_t}{dt} = v_\theta(x_t, t)

Selected Foundation Object

Keep the equation fixed; move through the evidence.

Concept 83 of 100Flow MatchGenerative Models / Phase 4: Generative modeling families
Current question

Diffusion = learn to denoise; flow = learn velocity directly

\frac{dx_t}{dt} = v_\theta(x_t, t)
PredictionCommit before the demo.

Ask what should change when the equation is manipulated, then let the visualization test that expectation.

EvidenceCompare local witness and source.

Use the runnable panel, the key equation, and canonical papers as separate forms of evidence for the same object.

InvariantName what survives notation changes.

The useful learning product is the reusable mechanism you can carry into another model, paper, or engineering tradeoff.

Next moveContinue in the newer notebook.

This atlas page keeps the working demo; the domain notebook carries the fuller Intuition -> Math -> Code -> Demo sequence.

Why It Matters for Modern Models

  • Simpler than diffusion: no noise schedule to tune
  • Rectified flows enable 1-4 step generation
  • State-of-the-art: Stable Diffusion 3 uses flow matching

What Tutorials Skip

What is still poorly explained in textbooks and papers:

  • Diffusion = learn to denoise; flow = learn velocity directly
  • Straight paths are easiest to approximate with few steps
  • Simulation-free: no sampling during training

Interactive Visualization

Core Math (Optional Deep Dive)

If you want intuition first, start with the key equation and the visualization. Come back here for the full walkthrough.

Key Equation
dxtdt=vθ(xt,t)\frac{dx_t}{dt} = v_\theta(x_t, t)

Learn vector field transporting noise to data:

dxtdt=vθ(xt,t)\frac{dx_t}{dt} = v_\theta(x_t, t)

Conditional flow matching:

L=Et,x0,x1[vθ(xt,t)ut2]\mathcal{L} = \mathbb{E}_{t, x_0, x_1}[\|v_\theta(x_t, t) - u_t\|^2]

Rectified flow: Straight paths xt=(1t)x0+tx1x_t = (1-t)x_0 + tx_1

ut=x1x0 (constant velocity)u_t = x_1 - x_0 \text{ (constant velocity)}

Canonical Papers

Flow Matching for Generative Modeling

Lipman et al.2023ICLR
Read paper →

Connections

Next Moves

Choose the next question to carry this object forward.