Challenges of Visually Realistic Augmented Reality Topics: Augmented, Mixed and Virtual Environments; Image-Based Modeling; Lighting and Appearance; Real-Time Graphics; Real-Time Rendering; Shadows, Translucency and Visibility In Proceedings of the 15th International Joint Conference on Computer Vision, Imaging and Computer Graphics Theory and Applications - Volume 0VISIGRAPP, 376-383, 2020 , Valletta, Malta