Mirror Metric v6
5-dimension sigmoid-mapped score — auto-computed from training — 100 = indistinguishable from a real 4K mirror
LPIPS perceptual distance — lower = more photorealistic. Sigmoid k=-20, midpoint=0.15. Inverted: 0.0 = perfect score.

ArcFace CSIM cosine similarity — does it look like the person? Sigmoid k=10, midpoint=0.65. 0.85+ = strong identity.
Mouth-region PSNR — dental quality is the product. Sigmoid k=0.30, midpoint=20 dB. The hardest region (teeth, tongue, mucosa).
Multi-scale structural similarity — captures structural fidelity at multiple resolutions. Sigmoid k=20, midpoint=0.88.

Full-face masked PSNR — overall reconstruction quality baseline. Sigmoid k=0.25, midpoint=28 dB.

Mirror Metric v6 is a research-backed quality score with five dimensions, each mapped through a sigmoid function for smooth, non-linear scoring. Mouth quality and perceptual fidelity are weighted highest because the dental region and photorealism are what patients examine most closely in the mirror.
[AUTO] All five dimensions are computed automatically from validation_log.csv (validation runs every 2.5K steps) with fallback to training_log.csv estimates. Sigmoid mapping provides smooth scoring without floor/ceiling clamp artifacts.
LPIPS (30%) — Learned perceptual image patch similarity. Lower values mean more photorealistic renders. The sigmoid is inverted (k=-20) so that lower LPIPS scores map to higher MM contributions. Midpoint at 0.15.
CSIM (25%) — ArcFace cosine similarity. A patient looking in a mirror must see themselves. 0.85+ = strong identity preservation. Sigmoid k=10, midpoint 0.65.
Mouth PSNR (20%) — The dental region is the product. Mouth-region PSNR is computed on a masked crop centered on the oral cavity. This is the hardest region to reconstruct (teeth, tongue, mucosa) and the most important for patient acceptance. Sigmoid k=0.30, midpoint 20 dB.
MS-SSIM (15%) — Multi-scale structural similarity captures structural fidelity across multiple resolutions, complementing the pixel-level PSNR and perceptual LPIPS metrics. Sigmoid k=20, midpoint 0.88.
Face PSNR (10%) — Full-face masked PSNR provides a stable baseline for overall reconstruction quality. Not a primary quality gate (Blau & Michaeli 2018), but useful for tracking convergence and regression. Sigmoid k=0.25, midpoint 28 dB.
Sources: NeRSemble benchmark (CSIM), Arc2Avatar, Cafca SIGGRAPH Asia 2024, Apple 3DGS Optimization 2025.