Zoomed-in line emitting regions from the TTauri models with R_in = 0.1 au for the P(10)v₁₋₀ (top left) and the P(4) v₂₋₁ line (top right). Middle and bottom rows: same for the models with R_in = 1.0  and 10 au.In each figure, the top panel shows the continuum optical depth (black line) and the line optical depth (blue line). Middle panel: cumulative line flux from vertical escape probability as a function of the radial distance from the star. Bottom panel: CO density in color scale with the region from which the vertical × radial integrated flux, amounting then to 49% of the total line flux, is emitted, and it is reported as numbers in the middle slice of each plot (black contours, 15-85% of the vertical and radial integrated line flux, dashed lines).