Effect of the four depth-based bias profiles on the metal-group fraction in a common central y-slice. All panels use identical geometry, material targets, correlation settings, stochastic seed, slice index, and color scale. The metal-group settings are: (a) unbiased; (b) inner bias, β_inner = 2.5; (c) outer bias, β_outer = 2.5; (d) depth bonus, β_depth = 2.5 and f_D = 0.25; (e) surface bonus, β_surf = 2.5 and f_D = 0.25; and (f) combined inner and surface biases, β_inner = β_surf = 2.5 and f_D = 0.25. All unlisted bias coefficients are zero. The common color scale gives the local metal-group fraction from 0 to 1.