findNodes

Find mesh nodes in specified region

Syntax

nodes = findNodes(mesh,"region",RegionType,RegionID)

nodes = findNodes(mesh,"box",xlim,ylim)

nodes = findNodes(mesh,"box",xlim,ylim,zlim)

nodes = findNodes(mesh,"radius",center,radius)

nodes = findNodes(mesh,"nearest",point)

Description

nodes = findNodes(mesh,"region",RegionType,RegionID) returns the IDs of the mesh nodes that belong to the specified geometric region.

nodes = findNodes(mesh,"box",xlim,ylim) returns the IDs of the mesh nodes within a bounding box specified by xlim and ylim. Use this syntax for 2-D meshes.

nodes = findNodes(mesh,"box",xlim,ylim,zlim) returns the IDs of the mesh nodes located within a bounding box specified by xlim, ylim, and zlim. Use this syntax for 3-D meshes.

nodes = findNodes(mesh,"radius",center,radius) returns the IDs of mesh nodes located within a circle (for 2-D meshes) or sphere (for 3-D meshes) specified by center and radius.

nodes = findNodes(mesh,"nearest",point) returns the IDs of mesh nodes closest to a query point or multiple query points with Cartesian coordinates specified by point.

Examples

Nodes Associated with Particular Edges and Faces

Find the nodes associated with a geometric region.

Create a PDE model.

model = createpde;

Include the geometry of the built-in function lshapeg. Plot the geometry.

geometryFromEdges(model,@lshapeg);
pdegplot(model,"FaceLabels","on","EdgeLabels","on")

Generate a mesh.

mesh = generateMesh(model,"Hmax",0.5);

Find the nodes associated with face 2.

Nf2 = findNodes(mesh,"region","Face",2);

Highlight these nodes in green on the mesh plot.

figure
pdemesh(model,"NodeLabels","on")
hold on
plot(mesh.Nodes(1,Nf2),mesh.Nodes(2,Nf2),"ok","MarkerFaceColor","g")  

Find the nodes associated with edges 5 and 7.

Ne57 = findNodes(mesh,"region","Edge",[5 7]);

Highlight these nodes in green on the mesh plot.

figure
pdemesh(model,"NodeLabels","on")
hold on
plot(mesh.Nodes(1,Ne57),mesh.Nodes(2,Ne57),"or","MarkerFaceColor","g")

Nodes Within Bounding Box

Find the nodes located within a specified box.

Create a PDE model.

model = createpde;

Import and plot the geometry.

importGeometry(model,"PlateHolePlanar.stl");
pdegplot(model)

Generate a mesh.

mesh = generateMesh(model,"Hmax",2,"Hmin",0.4, ...
                          "GeometricOrder","linear");

Find the nodes located within the following box.

Nb = findNodes(mesh,"box",[5 10],[10 20]);

Highlight these nodes in green on the mesh plot.

figure
pdemesh(model)
hold on
plot(mesh.Nodes(1,Nb),mesh.Nodes(2,Nb),"or","MarkerFaceColor","g")

Nodes Within Bounding Disk

Find the nodes located within a specified disk.

Create a PDE model.

model = createpde;

Import and plot the geometry.

importGeometry(model,"PlateHolePlanar.stl");
pdegplot(model)

Generate a mesh.

mesh = generateMesh(model,"Hmax",2,"Hmin",0.4, ...
                          "GeometricOrder","linear");

Find the nodes located within radius 2 from the center [5 10].

Nb = findNodes(mesh,"radius",[5 10],2);

Highlight these nodes in green on the mesh plot.

figure
pdemesh(model)
hold on
plot(mesh.Nodes(1,Nb),mesh.Nodes(2,Nb),"or","MarkerFaceColor","g")

Nodes Closest to Specified Points

Find the node closest to a specified point and highlight it on the mesh plot.

Create a PDE model.

model = createpde;

Import and plot the geometry.

importGeometry(model,"PlateHolePlanar.stl");
pdegplot(model)

Generate a mesh.

mesh = generateMesh(model,"Hmax",2,"Hmin",0.4);

Find the node closest to the point [15;10].

N_ID = findNodes(mesh,"nearest",[15;10])

N_ID = 
10

Highlight this node in green on the mesh plot.

figure
pdemesh(model)
hold on
plot(mesh.Nodes(1,N_ID),mesh.Nodes(2,N_ID),"or","MarkerFaceColor","g")

Input Arguments

mesh — Mesh object

Mesh property of a PDEModel object | output of generateMesh

Mesh object, specified as the Mesh property of a PDEModel object or as the output of generateMesh.

Example: model.Mesh

RegionType — Geometric region type

"Cell" | "Face" | "Edge" | "Vertex"

Geometric region type, specified as "Cell", "Face", "Edge", or "Vertex".

Example: findNodes(mesh,"region","Face",1:3)

Data Types: char

RegionID — Geometric region ID

vector of positive integers

Geometric region ID, specified as a vector of positive integers. Find the region IDs by using pdegplot.

Example: findNodes(mesh,"region","Face",1:3)

Data Types: double

xlim — x-limits of bounding box

two-element row vector

x-limits of the bounding box, specified as a two-element row vector. The first element of xlim is the lower x-bound, and the second element is the upper x-bound.

Example: findNodes(mesh,"box",[5 10],[10 20])

Data Types: double

ylim — y-limits of bounding box

two-element row vector

y-limits of the bounding box, specified as a two-element row vector. The first element of ylim is the lower y-bound, and the second element is the upper y-bound.

Example: findNodes(mesh,"box",[5 10],[10 20])

Data Types: double

zlim — z-limits of bounding box

two-element row vector

z-limits of the bounding box, specified as a two-element row vector. The first element of zlim is the lower z-bound, and the second element is the upper z-bound. You can specify zlim only for 3-D meshes.

Example: findNodes(mesh,"box",[5 10],[10 20],[1 2])

Data Types: double

center — Center of bounding circle or sphere

two-element row vector for a 2-D mesh | three-element row vector for a 3-D mesh

Center of the bounding circle or sphere, specified as a two-element row vector for a 2-D mesh or three-element row vector for a 3-D mesh. The elements of these vectors contain the coordinates of the center of a circle or a sphere.

Example: findNodes(mesh,"radius",[0 0 0],0.5)

Data Types: double

radius — Radius of bounding circle or sphere

positive number

Radius of the bounding circle or sphere, specified as a positive number.

Example: findNodes(mesh,"radius",[0 0 0],0.5)

Data Types: double

point — Cartesian coordinates of query points

2-by-N or 3-by-N matrix

Cartesian coordinates of query points, specified as a 2-by-N or 3-by-N matrix. These matrices contain the coordinates of the query points. Here, N is the number of query points.

Example: findNodes(mesh,"nearest",[15 10.5 1; 12 10 1.2])

Data Types: double

Output Arguments

nodes — Node IDs

positive integer | row vector of positive integers

Node IDs, returned as a positive integer or a row vector of positive integers.

Version History

Introduced in R2018a