Assign left/right to an (even unpaired, midline) object by self-mirror warping

A mini use-case of the package. An object that straddles the midline (a fly ellipsoid body, protocerebral bridge, ...) has no left/right label, yet every point still belongs to a hemisphere. We recover that the way a mirroring registration does (cf. bancr::banc_lr): reflect the object across a nominal midline plane and, optionally, refine the reflection with a Deformetrica warp of the object onto its own reflection so the true (possibly curved) symmetry surface is found. Each point is then labelled by how far and in which direction it must travel to reach its mirror partner - points on the symmetry surface barely move; points to one side travel toward the other.

Usage

mirror_lr_split(
  x,
  axis = c("X", "Y", "Z"),
  mid = NULL,
  refine = FALSE,
  band = 0,
  positive_travel = c("L", "R"),
  ...
)

Arguments

x

A mesh3d.

axis

Mirror axis, "X" (default), "Y" or "Z".

mid

Midline coordinate on axis (defaults to the extent midpoint).

refine

If TRUE, refine the flat reflection with a Deformetrica warp of x onto its reflection (finds a curved symmetry surface). Needs a working Deformetrica install; passes ... (e.g. kernel_width, device) through to deformetrica_register()/deformetrica_shoot().

band

Fraction of the axis extent within which |travel| is treated as midline ("M") rather than L/R. Default 0 (every point is L or R).

positive_travel

Which hemisphere a point that travels in the +axis direction belongs to ("L" default, or "R").

...

Passed to the Deformetrica calls when refine = TRUE.

Value

A list with L/R sub-meshes, a per-vertex side factor and the signed travel along axis.

See also

split_mesh_lr() for the plain-plane split.