# cellFaces

Find faces belonging to specified cells

Since R2021a

## Description

example

FaceID = cellFaces(g,RegionID) finds faces belonging to the cells with ID numbers listed in RegionID.

example

FaceID = cellFaces(g,RegionID,FilterType) returns internal, external, or all faces belonging to the cells with ID numbers listed in RegionID.

## Examples

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Find faces belonging to two cuboids in a geometry consisting of four stacked cuboids.

Create a geometry that consists of four stacked cuboids.

gm = multicuboid(5,10,[1 2 3 4],"ZOffset",[0 1 3 6])
gm =
DiscreteGeometry with properties:

NumCells: 4
NumFaces: 21
NumEdges: 36
NumVertices: 20
Vertices: [20x3 double]

Plot the geometry with the cell labels.

pdegplot(gm,"CellLabels","on","FaceAlpha",0.2)

Find faces belonging to cells 1 and 3.

faceIDs = cellFaces(gm,[1 3])
faceIDs = 1×12

1     2     3     4     5     6     7    12    13    14    15    16

Plot the geometry with the face labels.

pdegplot(gm,"FaceLabels","on","FaceAlpha",0.2)

Find faces belonging to the outer cuboid in a geometry consisting of two nested cuboids.

Create a geometry that consists of two nested cuboids of the same height.

gm = multicuboid([2 5],[4 10],3)
gm =
DiscreteGeometry with properties:

NumCells: 2
NumFaces: 12
NumEdges: 24
NumVertices: 16
Vertices: [16x3 double]

Plot the geometry with the cell labels.

pdegplot(gm,"CellLabels","on","FaceAlpha",0.2)

Find all faces belonging to the outer cell.

faceIDs = cellFaces(gm,2)
faceIDs = 1×10

3     4     5     6     7     8     9    10    11    12

Find only the internal faces belonging to the outer cell. Internal faces are faces shared between multiple cells.

faceIDs_int = cellFaces(gm,2,"internal")
faceIDs_int = 1×4

3     4     5     6

Find only the external faces belonging to the outer cell.

faceIDs_ext = cellFaces(gm,2,"external")
faceIDs_ext = 1×6

7     8     9    10    11    12

Plot the geometry with the face labels.

pdegplot(gm,"FaceLabels","on","FaceAlpha",0.2)

## Input Arguments

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3-D geometry, specified as an fegeometry object or a DiscreteGeometry object.

Cell ID, specified as a positive number or a vector of positive numbers. Each number represents a cell ID.

Type of faces to return, specified as "internal", "external", or "all". Depending on this argument, cellFaces returns these types of faces:

• "internal" — Internal faces, that is, faces shared between multiple cells.

• "external" — External faces, that is, faces not shared between multiple cells.

• "all" — All faces belonging to the specified cells.

## Output Arguments

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IDs of faces belonging to the specified cells, returned as a positive number or a vector of positive numbers.

## Version History

Introduced in R2021a

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