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Researchers compared two ways to tweak image attributes in pretrained neural backbones. The first uses a noisy image, inverts it to a hidden state, edits that state, then reconstructs an image. The second skips the hidden state entirely. Instead it moves the real image in small steps guided by differences in the model’s velocity field, so the image always stays on the training manifold.

On CelebA, the methods that perform inversion – SD3‑inv and FlowEdit – hit higher F1 scores on three of four attributes. However, the inversion‑free FlowEdit preserves identity better, showing lower LPIPS scores and a smaller visual shift from the original image. The experiment used a frozen 2‑Billion‑parameter SD3 backbone, the same for both pipelines, isolating the transport step.
| Effectiveness F1 ↑ | Realism FID ↓ | Identity LPIPS ↓ | |||||||||||
| Method | Backbone | a | g | br | bl | a | g | br | bl | a | g | br | bl |
| Explicit inversion — encoder; DDIM for Causal-Adapter, flow-ODE for SD3-inv | |||||||||||||
| VAE | deep-SCM | 0.390 | 0.990 | 0.284 | 0.004 | 60.0 | 63.4 | 59.9 | 57.4 | 0.283 | 0.295 | 0.283 | 0.284† |
| HVAE | deep-SCM | 0.246 | 0.742 | 0.476 | 0.122 | 2.2 | 5.9 | 25.6 | 31.7 | 0.026† | 0.076 | 0.138 | 0.229† |
| GAN | deep-SCM | 0.471 | 0.989 | 0.273 | 0.340 | 22.1 | 26.6 | 23.0 | 24.3 | 0.256 | 0.363 | 0.262 | 0.285 |
| Causal-Adapter | SD1.5 + adapter | 0.530 | 0.997 | 0.424 | 0.497 | 8.2 | 9.0 | 8.0 | 17.7 | 0.166 | 0.246 | 0.119 | 0.240 |
| SD3-inv | SD3 (2B, frozen) | 0.856 | 0.937 | 0.522 | 0.405 | 33.1 | 47.0 | 33.1 | 37.4 | 0.369 | 0.464 | 0.351 | 0.397 |
| Inversion Free | |||||||||||||
| FlowEdit | SD3 (2B, frozen) | 0.866 | 0.927 | 0.215 | 0.039 | 10.8 | 9.6 | 3.9 | 3.5 | 0.078 | 0.124 | 0.055 | 0.049† |
While inversion might appear more powerful, it introduces discretisation error. In a finite‑time inversion‑regeneration loop the error never cancels, leading to larger perceptual differences after a counterfactual change. The inversion‑free pipeline avoids this source of drift by accumulating velocity differences directly, a design that experimental results confirmed preserves identity.
Modeling counterfactuals without an explicit latent state is therefore a viable alternative when the goal is identity‑preserving edits. Ongoing work will test such pipelines on medical imaging, where higher‑fidelity edits are critical.