Multimodal generation drops joint training: SnB splits one diffusion trajectory and reuses pretrained models
Multimodal generation has largely relied on jointly training a shared latent variable from scratch, which scales poorly to high-resolution images. SnB instead couples separately pretrained unimodal diffusion models at sampling time: the modalities share one reverse trajectory up to a split point, then a bridge module routes each into its own branch. On CelebAMask-HQ, SnB reaches the lowest FID across all reported shared-fraction settings while keeping strong coherence; on PolyMNIST it trades wins with top-down methods.