Control Diffusion Conditioning with Classifier-Free Guidance
A conditional diffusion model can follow its conditioning signal more strongly at sampling time without a separate classifier. Classifier-free guidance does this by evaluating a model in conditional and unconditional modes, then amplifying the difference between those predictions. That difference is the central mechanism. The guidance scale does not simply make a prompt louder in an abstract sense. It changes the denoising prediction along a direction defined by what the conditioning input contributes relative to an unconditional prediction at the same noisy state.