Abstract We present a Geant4-based simulation study of the three-dimensional (3D) electromagnetic sampling calorimeter (ECAL). The 3D ECAL model consists of alternating layers of plastic scintillator and lead sheets where the scintillators are divided into strips and alternatively oriented in vertical and horizontal directions. With the energy deposits in the individual strips as a result of Geant4 simulation, the incidence angle of photons is reconstructed using the XGBoost with boosted decision trees. We report on the performance of the directional measurement which depends on both detector configuration and the maturity of the training.