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Weighted cylinder surface helpers

Source: R/export_examples.R, R/graph_helpers.R
cylinder_surface_helpers.Rd

Convenience helpers that embed a cylindrical grid graph into \(\mathbb{R}^3\) and use the induced Euclidean edge lengths as positive graph weights. These helpers are intended for benchmark families where the graph topology is cylindrical but the intended metric comes from a curved or spatially varying 3D realization.

Usage

cylinder.surface.graph(
  h,
  w = h,
  surface = c("barrel", "hourglass", "wavy"),
  radius = 1,
  height = 2,
  amplitude = 0.3,
  freq_theta = 2,
  freq_z = 1,
  twist = 0.25,
  normalize = c("median", "mean", "none")
)

Arguments

h

Number of rows.

w

Number of columns. Defaults to h.

surface

Cylinder surface family. One of "barrel", "hourglass", or "wavy".

radius

Positive baseline cylinder radius.

height

Positive cylinder height.

amplitude

Finite numeric deformation amplitude. The resulting radius profile must stay positive everywhere.

freq_theta

Positive angular frequency used only when surface = "wavy".

freq_z

Positive vertical frequency used only when surface = "wavy".

twist

Finite angular twist applied linearly with height.

normalize

Normalization applied to the induced edge lengths. One of "median", "mean", or "none".

Value

The coords_surface component is an n x 3 numeric matrix with columns x, y, and z.

cylinder.surface.graph() returns a list with components:

  • edges: the undirected cylindrical-grid edges,

  • n: number of vertices,

  • edge_weights: induced positive edge lengths,

  • coords_surface: the 3D surface embedding,

  • coords_param: the 2D unwrapped parameter coordinates,

  • weight_scale: the normalization constant applied to the raw edge lengths,

  • family: always "cylinder",

  • surface: the chosen surface name,

  • label: a human-readable family label.

Details

The coords_surface component contains the 3D coordinates of the embedded cylindrical grid. cylinder.surface.graph() returns a reusable weighted-graph bundle containing the cylinder edges, induced edge weights, the 3D surface coordinates, and a 2D unwrapped parameterization.

Examples

cylinder <- cylinder.surface.graph(4, 5, surface = "hourglass")