Shadow X-ray Magnetic Circular Dichroism Photo-Emission Electron Microscopy(XMCD-PEEM) is a recent technique, in which the photon intensity in the shadowof an object lying on a surface, may be used to gather information about thethree-dimensional magnetization texture inside the object. Our purpose here isto lay the basis of a quantitative analysis of this technique. We first discussthe principle and implementation of a method to simulate the contrast expectedfrom an arbitrary micromagnetic state. Text book examples and successfulcomparison with experiments are then given. Instrumental settings are finallydiscussed, having an impact on the contrast and spatial resolution : photonenergy, microscope extraction voltage and plane of focus, microscope backgroundlevel, electric-field related distortion of three-dimensional objects, Fresneldiffraction or photon scattering.