GMP 2021 will be held from May 10 to May 13, 2021 at Pilsen/Plzen, Czech Republic. It is a part of an annual international conference series on geometric modeling, simulation, and computing. It is an international forum for presenting and discussing new trends and results in theory, techniques, and applications of both mathematical and computational aspects of modeling and processing of geometric data. This is especially important for many applied disciplines such as computer graphics, computer vision, CAD/CAM, robotics, scientific computing, medical imaging, engineering analysis, etc.