# 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

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.

## Properties

expand all

Number of geometry cells, specified as a nonnegative integer.

Data Types: double

Number of geometry faces, specified as a positive integer.

Data Types: double

Number of geometry edges, specified as a nonnegative integer.

Data Types: double

Number of geometry vertices, specified as a nonnegative integer.

Data Types: double

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

collapse all

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: [6x3 double]

Plot the geometry.

pdegplot(gm,FaceAlpha=0.5)

Import a geometry from an STL geometry file.

gm =
DiscreteGeometry with properties:

NumCells: 1
NumFaces: 147
NumEdges: 329
NumVertices: 213
Vertices: [213x3 double]

Plot the geometry,

pdegplot(gm)

## Version History

Introduced in R2015a