# RegionBoundary

RegionBoundary[reg]

represents the boundary of the region reg.

# Details # Examples

open allclose all

## Basic Examples(2)

The boundary of a disk:

Compute the circumference of the disk:

The boundary of a MeshRegion:

Compute the arc length of the perimeter:

## Scope(13)

### Special Regions(5)

The boundary of a Line in 1D is a set of points:

Count the number of points:

Visualize it:

The boundary of a Polygon in 2D is a Line object:

Compute the length of the perimeter of the polygon:

Visualize it:

The boundary of a Disk is a Circle:

Compute the circumference:

Substitute in a value for to visualize it:

The boundary of a Ball is a Sphere:

Compute the surface area:

Visualize it:

The boundary of a unit ball in 7D:

This cannot be visualized, but can still be computed with:

### Mesh Regions(6)

The boundary of a BoundaryMeshRegion in 1D:

Visualize it overlaid on the original region:

The boundary of a MeshRegion in 1D:

Visualize it overlaid on the original region:

The boundary of a BoundaryMeshRegion in 2D:

Compute the length of the perimeter:

Visualize it overlaid on the original region:

The boundary of a MeshRegion in 2D:

Compute the length of the boundary:

The boundary of a BoundaryMeshRegion in 3D:

Compute the surface area:

The boundary of a MeshRegion in 3D:

Compute the surface area:

### Geographic Regions(2)

The boundary of a polygon with GeoPosition:

The boundary of a polygon with GeoGridPosition:

## Properties & Relations(5)

The dimension of RegionBoundary for a full-dimensional region is one dimension less:

The dimension of RegionBoundary for a lower-dimensional region is the same:

RegionBoundary of a lower-dimensional region is the region itself:

The boundary of a boundary is the boundary itself:

The boundary consists of points for which SignedRegionDistance is zero: