nx_epose.nx

nx_epose.nx -- ESSENTIAL MATRIX -> RELATIVE POSE (R, t) decomposition (cadtwin P1, completes photo->pose->3D). The last link of two-view SfM: given E (from nx_essential3d), recover the camera rotation R + translation direction t. Classical SVD decomposition E = U diag(s,s,0) V^T -> R = U W V^T (or U W^T V^T), t = u3; the 4 (R,t) candidates are disambiguated by CHEIRALITY (points in front of both cameras). SVD done SVD-FREE: V = eigenvectors of E^T E (power-iteration dominant + null; v2 = v3 x v1), and U DERIVED from E V (consistent, avoids the repeated-singular-value ambiguity). All Q14 fixed-point. Composes nx_recon3d (vec math + triangulate for cheirality). license_tier: ORIGINAL