Comparison of the 1D and 3D method for computing chromospheric heating due to absorption of coronal radiation. All panels show a vertical slice through a snapshot of a three-dimensional radiation-MHD simulation performed with Bifrost. The red curve is located at a gas temperature of 30 000 K and indicates the location of the transition zone. All brightness ranges have been clipped to bring out variation at low values of the displayed quantities. Panels, from top to bottom: coronal emissivity η; angle-averaged radiation field computed in 3D; angle-averaged radiation field computed in 1D: heating rate per mass with 3D radiation: heating rate per mass with 1D radiation. Note that the 3D radiation field is computed using the full 3D volume, not only this 2D slice.