  We present our work on the simulation of the early stages of heavy-ion
collisions with finite longitudinal thickness in the laboratory frame in 3+1
dimensions. In particular we study the effects of nuclear thickness on the
production of a glasma state in the McLerran-Venugopalan model within the color
glass condensate framework. A finite thickness enables us to describe nuclei at
lower energies, but forces us to abandon boost-invariance. As a consequence,
random classical color sources within the nuclei have to be included in the
simulation, which is achieved by using the colored particle-in-cell (CPIC)
method. We show that the description in the laboratory frame agrees with
boost-invariant approaches as a limiting case. Furthermore we investigate
collisions beyond boost-invariance, in particular the pressure anisotropy in
the glasma.
