discreteGeometry

Discrete 2-D or 3-D geometry description

Description

DiscreteGeometry describes a 2-D or 3-D geometry in the form of a discrete geometry object. PDEModel, StructuralModel, and ThermalModel objects have a Geometry property, which can be an AnalyticGeometry or DiscreteGeometry object.

Creation

Syntax

gm = discreteGeometry(fegeom)

Description

Create a discrete geometry for your model by using one of the following approaches:

• Use importGeometry to import a 2-D or 3-D geometry from an STL file or a 3-D geometry from a STEP file and attach it to the model.

• Use geometryFromMesh to reconstruct a 2-D or 3-D geometry from mesh and attach it to the model.

• Use multicuboid, multicylinder, or multisphere to create a 3-D geometry. Then assign the resulting geometry to the Geometry property of the model. For example, create a PDE model and add the following geometry formed by three spheres to the model.

  model = createpde;
  gm = multisphere([1,2,3]);
  model.Geometry = gm;

• Use extrude to create a 3-D geometry by vertically extruding a 2-D geometry.

In R2026a: gm = discreteGeometry(fegeom) converts an fegeometry object to a Discretegeometry object.

Input Arguments

fegeom — Geometry to convert

fegeometry object

Since R2026a

Geometry to convert, specified as an fegeometry object. The geometry must not be empty.

Properties

NumCells — Number of geometry cells

nonnegative integer

Number of geometry cells, specified as a nonnegative integer.

Data Types: double

NumFaces — Number of geometry faces

positive integer

Number of geometry faces, specified as a positive integer.

Data Types: double

NumEdges — Number of geometry edges

nonnegative integer

Number of geometry edges, specified as a nonnegative integer.

Data Types: double

NumVertices — Number of geometry vertices

nonnegative integer

Number of geometry vertices, specified as a nonnegative integer.

Data Types: double

Vertices — Coordinates of geometry vertices

N-by-2 numeric matrix | N-by-3 numeric matrix

Coordinates of geometry vertices, specified as an N-by-2 or N-by-3 numeric matrix for a 2-D or 3-D geometry, respectively. Here, N is the number of vertices.

Data Types: double

Object Functions

addCell	Combine two geometries by adding one inside a cell of another
addFace	Fill void regions in 2-D and split cells in 3-D geometry
addVertex	Add vertex on geometry boundary
addVoid	Create void regions inside 3-D geometry
cellEdges	Find edges belonging to boundaries of specified cells
cellFaces	Find faces belonging to specified cells
extrude	Vertically extrude 2-D geometry or specified faces of 3-D geometry
faceEdges	Find edges belonging to specified faces
facesAttachedToEdges	Find faces attached to specified edges
mergeCells	Merge geometry cells
nearestEdge	Find edges nearest to specified point
nearestFace	Find faces nearest to specified point
rotate	Rotate geometry
scale	Scale geometry
translate	Translate geometry

Examples

Nested Cylinders Geometry

Create the geometry consisting of three cylinders of the same height by using the multicylinder function.

gm = multicylinder([5 10 15],20)

gm = 
  DiscreteGeometry with properties:

       NumCells: 3
       NumFaces: 9
       NumEdges: 6
    NumVertices: 6
       Vertices: [6×3 double]

Plot the geometry.

pdegplot(gm,FaceAlpha=0.5)

Geometry from STL File

Import a geometry from an STL geometry file.

gm = importGeometry("ForearmLink.stl")

gm = 
  DiscreteGeometry with properties:

       NumCells: 1
       NumFaces: 147
       NumEdges: 329
    NumVertices: 213
       Vertices: [213×3 double]

Plot the geometry,

pdegplot(gm)

DiscreteGeometry from fegeometry

Since R2026a

Create a geometry by cutting out multiple cubes from a cylinder.

First, create geometries representing a cylinder and a unit cube.

gmcyl = fegeometry(multicylinder(1,1));
gmcube = fegeometry(multicuboid(1,1,1));

Create a vector of geometries by rotating the cube by 30 and 60 degrees.

angle = [0 30 60];
for k = 1:numel(angle)
    gv(k) = rotate(gmcube,angle(k));
end

Subtract the resulting vector of geometries from the cylinder.

gm = subtract(gmcyl,gv)

gm = 
  fegeometry with properties:

       NumCells: 1
       NumFaces: 27
       NumEdges: 74
    NumVertices: 50
       Vertices: [50×3 double]
           Mesh: []

Plot the resulting geometry.

pdegplot(gm)

The resulting geometry is an fegeometry object. You can use this object to define a geometry for an femodel object or batteryP2DModel object. To use this geometry with a PDEModel object for solving general PDEs, convert the geometry to a DiscreteGeometry object.

gm = discreteGeometry(gm)

gm = 
  DiscreteGeometry with properties:

       NumCells: 1
       NumFaces: 27
       NumEdges: 74
    NumVertices: 50
       Vertices: [50×3 double]

Create a PDE model and include the geometry in the model.

model = createpde;
model.Geometry = gm

model = 
  PDEModel with properties:

           PDESystemSize: 1
         IsTimeDependent: 0
                Geometry: [1×1 DiscreteGeometry]
    EquationCoefficients: []
      BoundaryConditions: []
       InitialConditions: []
                    Mesh: []
           SolverOptions: [1×1 pde.PDESolverOptions]

Version History

Introduced in R2015a

R2026a: discreteGeometry creates a DiscreteGeometry object from an fegeometry object

The discreteGeometry function converts an fegeometry object to a DiscreteGeometry object.