The open source software SCoPI written in C++ is designed for the Simulation of Interacting Particle Collections. It enables 2D and 3D simulation of particles (with convex shape), interacting with a surrounding medium (obstacles of various types, moving or not, gravity force, possible coupling with a fluid solver) as well as with other particles (inter-particle forces, contacts). The contact model used is of the Contact Dynamics type [1, 2]. It can be dry (inelastic, with or without friction) or viscous (modeling the force of lubrication in a viscous fluid [3]). The algorithms used are implicit and reduce, at each time step, to the solution of a constrained convex problem. The latter can be solved either using the Mosek library, or via projected gradient or accelerated projected gradient algorithms. In the context of an inelastic contact model, it has been used, for example, to study the local rheology of a granular material in front of a towed sphere [3]. [1] Jean, Michel et Moreau, Jean Jacques. Unilaterality and dry friction in the dynamics of rigid body collections. In : 1st contact mechanics international symposium. 1992. p. 31-48. [2] Maury, Bertrand. A time-stepping scheme for inelastic collisions. Numerische Mathematik, 2006, vol. 102, p. 649-679. [3] Lefebvre, Aline. Numerical simulation of gluey particles. ESAIM: Mathematical Modelling and Numerical Analysis, 2009, vol. 43, no 1, p. 53-80. [4] Seguin, A., Lefebvre-Lepot, Aline, Faure, Sylvain, et Gondret, Philippe. Clustering and flow around a sphere moving into a grain cloud. The European Physical Journal E, 2016, vol. 39, no 6, p. 63.