Applied CAD Systems and Applications Based on the C3D Geometric Modeling Kernel, Used For the Design of Products with Functional Curves / V.G. Muftejev, А. Maximenko, R.I. Akhmetshin , A.P. Zelev, Rushan Ziatdinov, F.T. Ziganshina, R.I. Nabiyev, I.M. Farkhutdinov , M.M. Fattakhov / Geometric Modelling. Computer Graphics in education GraphiCon 2021