for i in range(number_R_steps):
            self.addComputePerDof("x", "x + ((dt / {}) * v)".format(number_R_steps * 2))
            self.addComputePerDof("x1", "x")  # save pre-constraint positions in x1
            self.addConstrainPositions()  # x is now constrained
            self.addComputePerDof(