  Context. The model of disc fragmentation due to gravitational instabilities
offers an alternate formation mechanism for gas giant planets, especially those
on wide orbits. Aims. Our goal is to determine the 3D structure of
disc-instability protoplanets and to examine how this relates to the thermal
physics of the fragmentation process. Methods. We modelled the fragmentation of
gravitationally unstable discs using the SPH code PHANTOM, and followed the
evolution of the protoplanets formed through the first and second-hydrostatic
core phases (up to densities 1e-3 g/cm3). Results. We find that the 3D
structure of disc-instability protoplanets is affected by the disc environment
and the formation history of each protoplanet (e.g. interactions with spiral
arms, mergers). The large majority of the protoplanets that form in the
simulations are oblate spheroids rather than spherical, and they accrete faster
from their poles. Conclusions. The 3D structure of disc-instability
protoplanets is expected to affect their observed properties and should be
taken into account when interpreting observations of protoplanets embedded in
their parent discs.
