COMSOL 6.4 - Retrieving Geometry Information

With the function mphgeominfo you can access detailed information of a geometry object as well its data.

To get the information of a geometry object enter the command:

where <geomtag> is the tag of either a geometry node or a part geometry node you want the information from. In case of the model has only geometry node, the tag <geomtag> is optional.

The output info is a MATLAB® structure. The default fields available in the structure are listed in the table:


Fields	Description
tag	Tag of the geometry
sdim	Space dimension
label	Label of the selected geometry object
component	Tag of the component
geometricmodel	Node defining the geometry for the physics
ispart	Geometry is a part
isaxisymmetric	Geometry is axisymmetric
isassembly	Geometry is an assembly
isvirtual	Geometry is using virtual geometry features
ismesh	Geometric model is defined by a mesh rather than a geometry
autobuildnew	Build geometric operation automatically when added
autorebuild	Geometry sequence automatically rebuilt
lengthunit	Current length unit
angularunit	Current angular unit
objectnames	Names of all objects that exist in the current state
current	Tag of the current feature
geomrep	Geometry representation
scaleunitvalue	Scale numeric values in the geometry and meshing sequences
repairtol	Relative repair tolerance
repairtoltype	Repair tolerance type
absrepairtol	Absolute repair tolerance
useconstrdim	Constraints and dimensions functionality enabled
constrdimbuild	Constraints and dimensions used when building the geometry object
constrdimstatus	Overall status of the constraints and dimensions
designbooleans	Perform booleans using the Design Module
view	Current view
exists	Geometry object exists
boundingbox	Bounding box of the geometry objects
type	Object type
Ndomains	Number of domains
Nboundaries	Number of boundaries
Nedges	Number of edges
Nvertices	Number of vertices
Nfinitevoids	Number of finite voids
Nfaces	Number of faces
problems	List of error/warning messages

In addition to geometry information, you can retrieve geometric entity data, such as local parameters, coordinates, curvature, up and down domain indices, and so on. To get the geometry data enter:

[info, data] = mphgeominfo(model, <geomtag>, 'entity', <entitytype>);

where <entitytype> is the type of the entity to get the data from. It can be either 'face', 'edge', or 'vertex'.

data is a MATLAB structure which fields depend on the entity type. These are listed in the table below:


Fields	Entity	Description
domainnumber	vertex	Domain index for isolated vertices
edgex	edge	Edge coordinates
edgedx	edge	Edge first order derivatives
edgeddx	edge	Edge second order derivatives
edgecurvature	edge	Edge curvature values
edgenormal	edge	Edge normal values (in 2D only)
edgetorsion	edge	Edge torsion values (in 3D only)
facex	face	Face coordinates
facedx	face	Face first order derivatives
faceddx	face	Face second order derivatives
facenormal	face	Face normal
faceff1	face	Face first fundamental form
faceff2	face	Face second fundamental form
facegausscurvature	face	Face Gauss curvature
meancurvature	face	Face mean curvature
updown	face\|edge	Up and down domain indices
p	vertex	Vertex coordinates
paramrange	face\|edge	Parameter ranges

In addition you can specify a selection of the entity type to get the data from as in the command below:

[info, data] = mphgeominfo(model, <geomtag>, ...

'entity', <entitytype>, 'selection', <sel>);

where <sel> is an array of entity numbers.

The geometric data are evaluated within the local parameter range on a structured grid for faces or interval for edge, with default sizes of 10-by-10 and 10, respectively. To change the size of geometric data evaluation point use the steps property as in the command below:

[info, data] = mphgeominfo(model, <geomtag>, ...

'entity', <entitytype>, 'selection', <sel>, 'steps', <steps>);

where <steps> is an integer or a NxM integer array for a face type in case you need to evaluate the data on an uneven grid.


	To retrieve the detailed information about the geometry in a model using the COMSOL API, see Geometric Model Information Methods in the COMSOL Multiphysics Programming Reference Manual.

Retrieving Geometry Information

This example shows how to use mphgeominfo to retrieve geometry information.

First create a simple 3D geometry:

model = ModelUtil.create('Model');

comp1 = model.component.create('comp1',true);

geom1 = comp1.geom.create('geom1', 3);

geom1.feature.create('blk1','Block');

geom1.feature.create('con1','Cone');

geom1.run;

To visualize the geometry in a MATLAB figure window enter:

mphgeom(model)

As only one geometry node is available in the model, to access the geometry information enter:

info = mphgeominfo(model)

To determine the space dimension of the geometry, enter:

info.sdim

To inquire about the number of domains and the number of boundaries:

info.Ndomains

info.Nboundaries

The bounding box coordinates of the geometry are accessible using:

info.boundingbox

To get the geometry data for the face number 1 enter the command:

[info, data] = mphgeominfo(model, 'geom1', 'entity', 'face',...

'selection', 1);

To get the range of the surface parameters enter:

data.paramrange

this returns a 4-by-1 array following the given format: [s1min; s1max; s2min; s2max] where s1min and s1max are the minimum, and maximum respectively, of the first surface parameter. s2min and s2max are the minimum, and maximum respectively, of the second surface parameter.

To evaluate the face coordinates, in the global coordinate system, enter:

data.facex

The face coordinates are evaluated with the local parameter range on a 10 x 10 points grid. If you want to reduce or increase the size of evaluation grid, use the property 'steps'. For instance to evaluate the face coordinates on a 5 x 10 grid enter:

[info, data] = mphgeominfo(model, 'geom1', 'entity', 'face',...

'selection', 1,'steps', [5 10]);

To get the parameter range of an edge and, for example, to get the length of edge number 3, enter:

[info, data] = mphgeominfo(model, 'geom1', 'entity', 'edge',...

'selection', 3);

paramrange = data.paramrange;

edgelength = paramrange(end)

To get the coordinates and the curvature data at the middle of edge number 3 enter:

[info, data] = mphgeominfo(model, 'geom1', 'entity', 'edge',...