template<class Real, class Mem = peclet::core::MemSpace>
struct peclet::voro::SdfSpheres< Real, Mem >
Periodic UNION of solid balls: sdf(x) = min_i(|x−c_i|_minimage − r_i) (<0 inside a ball, >0 in the fluid). Device-callable; holds Views of the centres (3M, x-fastest c_{ix},c_{iy},c_{iz}) and radii (M). L > 0 ⇒ periodic min-image (L = box edge); L ≤ 0 ⇒ non-periodic. The packed-bed / pore-space wall geometry for the volume mesh optimiser. Mem is the memory space the centre / radius views live in: the device space (default) for the tessellator's kernels, Kokkos::HostSpace for a host-side caller (the pore-cell oracle).