  Supernova remnant (SNR) shocks provide favourable sites of cosmic ray (CR)
proton acceleration if the local magnetic field direction is quasi-parallel to
the shock normal. Using the moving-mesh magneto-hydrodynamical (MHD) code AREPO
we present a suite of SNR simulations with CR acceleration in the Sedov-Taylor
phase that combine different magnetic field topologies, density distributions
with gradients and large-scale fluctuations, and -- for our core-collapse SNRs
-- a multi-phase interstellar medium with dense clumps with a contrast of
$10^4$. Assuming the hadronic gamma-ray emission model for the TeV gamma-ray
emission, we find that large-amplitude density fluctuations of
$\delta\rho/\rho_0\gtrsim75$ per cent are required to strongly modulate the
gamma-ray emissivity in a straw man's model in which the acceleration
efficiency is independent of magnetic obliquity. However, this causes strong
corrugations of the shock surface that are ruled out by gamma-ray observations.
By contrast, magnetic obliquity-dependent acceleration can easily explain the
observed variance in gamma-ray morphologies ranging from SN1006 (with a
homogeneous magnetic field) to Vela Junior and RX J1713 (with a turbulent
field) in a single model that derives from plasma particle-in-cell simulations.
Our best-fit model for SN1006 has a large-scale density gradient of $
\nabla{n}\simeq 0.0034~\mathrm{cm}^{-3}~\mathrm{pc}^{-1} $ pointing from
south-west to north-east and a magnetic inclination with the plane of the sky
of $\lesssim10^\circ$. Our best-fit model for Vela Junior and RX J1713 adopts a
combination of turbulent magnetic field and dense clumps to explain their TeV
gamma-ray morphologies and moderate shock corrugations.
