x1 is the conceptualized/ideal/abstract shape of a biconvex lens formed by/manifested from the intersection x2 (parameters) of two-dimensional circular disks immersed (embedded) in geometry/defined by metric x3; x1 is the convex-only region bounded by intersecting circular arcs given by x2
May not be symmetric (statement to such end can be made by specifying parameters of circular disks via x2). This shape is "filled", being formed by the intersection of disks. Contrast with: tairmlunra. See also: cuktai