findCell

Find cells by coordinates of points located inside them

Since R2025a

Syntax

cellIDs = findCell(g,Coords)

Description

cellIDs = findCell(g,Coords) returns the IDs of the cells containing query points with Cartesian coordinates Coords. The function returns NaN values for points located outside of the geometry. For query points located on a boundary and, therefore, belonging to more than one cell, the function returns the lowest cell ID.

Examples

Find Cell IDs by Coordinates

Identify cells in a geometry of nested spheres.

Create and plot the geometry representing 10 nested spheres.

g = fegeometry(multisphere(1:10));
pdegplot(g,FaceAlpha=0.3)

Create a matrix of query points.

QP = zeros(10,3);
QP(:,1) = (1:10).'-0.1

QP = 10×3

    0.9000         0         0
    1.9000         0         0
    2.9000         0         0
    3.9000         0         0
    4.9000         0         0
    5.9000         0         0
    6.9000         0         0
    7.9000         0         0
    8.9000         0         0
    9.9000         0         0

Identify cells where these points are located.

cellID = findCell(g,QP)

cellID = 1×10

     1     2     3     4     5     6     7     8     9    10

For points outside the geometry, findCell returns NaN.

cellID = findCell(g,[15 0 0])

cellID = 
NaN

For query points located on the boundaries and, therefore, belonging to more than one cell, findCell returns the lowest cell ID.

QP(:,1) = (1:10).'

QP = 10×3

     1     0     0
     2     0     0
     3     0     0
     4     0     0
     5     0     0
     6     0     0
     7     0     0
     8     0     0
     9     0     0
    10     0     0

cellID = findCell(g,QP)

cellID = 1×10

     1     2     3     4     5     6     7     8     9    10

Modify Geometry by Deleting Cells

Modify the damping mounts geometry by deleting two mounts located diagonally.

Import the geometry representing four damping mounts.

g = fegeometry("DampingMounts.stl")

g = 
  fegeometry with properties:

       NumCells: 4
       NumFaces: 16
       NumEdges: 16
    NumVertices: 16
       Vertices: [16×3 double]
           Mesh: []

Plot the imported geometry. The geometry has four cells: one cell representing each mount.

pdegplot(g)

Find the IDs of the cells containing the points with these coordinates: (50,250,50) and (1450,1200,50).

cellIDs = findCell(g,[50 250 50; 1450 1200 50])

cellIDs = 1×2

     2     3

Show the two points on the geometry plot.

pdegplot(g,FaceAlpha=0.3,CellLabels="on")
hold on
scatter3([50 1450],[250 1200],[50 50],"filled","red")

Delete the cells containing the points with the specified coordinates.

g = deleteCell(g,cellIDs)

g = 
  fegeometry with properties:

       NumCells: 2
       NumFaces: 8
       NumEdges: 8
    NumVertices: 8
       Vertices: [8×3 double]
           Mesh: []

Plot the resulting geometry.

figure
pdegplot(g,CellLabels="on",FaceAlpha=0.3)

Input Arguments

g — 3-D geometry

fegeometry object

3-D geometry, specified as an fegeometry object.

Coords — Query point coordinates

N-by-3 numeric matrix

Query point coordinates, specified as an N-by-3 numeric matrix. Here, N is the number of query points.

Output Arguments

cellIDs — Cell IDs

N-by-1 vector of positive integers and NaN values

Cell IDs, returned as an N-by-1 vector of positive integers and NaN values. The function returns positive integers for query points located in a cell of a geometry, and NaN values for points located outside of the geometry. For query points located on a boundary (face, edge, or vertex) and, therefore, belonging to more than one cell, the function returns the lowest cell ID.

Version History

Introduced in R2025a