Solutions for the standard spherically symmetric models as calculated with the 3D FVM (blue) and 3D SC methods using linear (red) or Bézier (green) interpolations, compared to an accurate 1D solution (black solid line). The dots represent the solutions at specific grid points (with different latitudes and longitudes), where only a subset of all grid points is displayed to compress the image. Corresponding errors are indicated at the bottom of each chart. Top panel: mean intensity for the continuum transfer as a function of radius, with ϵ_C = 10⁻⁶, and k_C = [1, 10, 100] from left to right. Bottom panel: line source function with ϵ_L = 10⁻⁶, and k_L = [10⁰, 10³, 10⁵] from left to right.