  Forward modeling of wave scattering and radar imaging mechanisms is the key
to information extraction from synthetic aperture radar (SAR) images. Like
inverse graphics in optical domain, an inherently-integrated forward-inverse
approach would be promising for SAR advanced information retrieval and target
reconstruction. This paper presents such an attempt to the inverse graphics for
SAR imagery. A differentiable SAR renderer (DSR) is developed which
reformulates the mapping and projection algorithm of SAR imaging mechanism in
the differentiable form of probability maps. First-order gradients of the
proposed DSR are then analytically derived which can be back-propagated from
rendered image/silhouette to the target geometry and scattering attributes. A
3D inverse target reconstruction algorithm from SAR images is devised. Several
simulation and reconstruction experiments are conducted, including targets with
and without background, using both synthesized data or real measured inverse
SAR (ISAR) data by ground radar. Results demonstrate the efficacy of the
proposed DSR and its inverse approach.
