Illustration of the wrapper geometry, showing RGB composite maps of carbon-bearing species for different radii of curvature. The color encodes the local abundances as follows: red for ionized carbon (C⁺), green for neutral atomic carbon (C), and blue for carbon monoxide (CO). Areas where these species coexist appear as color blends (e.g., cyan for C and CO, yellow for C⁺ and C, white for equal contributions). The left panel shows a curvature radius of R_C = 0.05 pc, the middle to R_C = 0.2 pc, and the right to R_C = 0.5 pc. These maps highlight the local spherical curvature in the plane of the sky, with the observer located at the bottom of each panel and the stellar radiation field entering from the right. Radiative transfer is computed along vertical lines from top to bottom in this configuration. The abundances originate from a single Meudon PDR model (P_th = 4 × 10⁶ K cm⁻³, G₀ = 100). The usual edge-on representation of abundances of this model can be found in Figure 10.