2. Mapped Mesh Generation - MapMesh, ExtMesh

CEETRON Mesh supports the creation of finite element meshes using various mapped mesh generation techniques. The MapMesh module supports basic mapped mesh generation technology in which structured grids of nodes and elements are created within the parameter space of linear, parabolic or cubic hyperpatches. The ExtMesh module supports the generation of nodes and elements extruded from a given “cross section” represented by a general unstructured mesh.

2.1. Mapped Mesh Generation - MapMesh

The MapMesh module provides simple mapped mesh generation. The basic notion is to specify a parametrically defined parent domain or patch which represents the boundaries of a 1D, 2D or 3D region in space. The coordinate system in which the patch point coordinates are expressed can be changed so that generating finite element nodes in cylindrical or spherical coordinate systems or arbitrarily oriented and positioned coordinate systems is possible. Once defined, the parent patch is subdivided at regular intervals in parameter space to generate finite elements. The number of elements in each of the parametric directions of the parent patch may be specified. The patch basis functions are currently limited to linear, parabolic and cubic Serendipity and Lagrange polynomials on line, quadrilateral and hexahedral patch topologies. This technique can generate large numbers of elements very efficiently.

The functions associated with a MapMesh object are the following.

Instance a MapMesh object using vis_MapMeshBegin(). Once a MapMesh object is instanced, define the number of points and patches to be input using vis_MapMeshDef(). Define point locations using vis_MapMeshSetPoint() and patch connectivity using vis_MapMeshSetPatch(). The point coordinates defined by vis_MapMeshSetPoint() are assumed by default to be expressed in the global Cartesian coordinate system. However this basic coordinate system can be changed to a cylindrical or spherical system by defining a CoordSys object and specifying it using vis_MapMeshSetCoordSys(). Use vis_MapMeshSetParami() to define the overall order and topology (Serendipity or Lagrange) of the finite elements to be generated. Use vis_MapMeshSetPatchParami() to set the shape and the number of elements to generate in each direction of each patch. The user is able to define integer associations at points and patch edges and faces which will be assigned to the node or nodes generated on the respective entity. These associations are useful for identifying nodes and elements for the application of boundary conditions. The function vis_MapMeshSetPointAssoc() is used to set associations at nodes generated at defined points, while the function vis_MapMeshSetPatchAssoc() is used to set associations for nodes generated along the edges and faces of the parent patch. Finally the function vis_MapMeshGenerate() generates the nodes and finite elements and enters them into a Connect object.

2.2. Function Descriptions

The currently available MapMesh functions are described in detail in this section.

vis_MapMesh *vis_MapMeshBegin(void)

create an instance of a MapMesh object

Create an instance of a MapMesh object. Memory is allocated for the object private data and the pointer to the data is returned. The default basic coordinate system is the global Cartesian coordinate system.

Destroy an instance of a MapMesh object using

void vis_MapMeshEnd (vis_MapMesh *mapmesh)

Return the current value of a MapMesh object error flag using

Vint vis_MapMeshError (vis_MapMesh *mapmesh)

Returns

The function returns a pointer to the newly created MapMesh object. If the object creation fails, NULL is returned.

void vis_MapMeshEnd(vis_MapMesh *p)

destroy an instance of a MapMesh object

See vis_MapMeshBegin()

Vint vis_MapMeshError(vis_MapMesh *p)

return the current value of a MapMesh object error flag

See vis_MapMeshBegin()

void vis_MapMeshDef(vis_MapMesh *p, Vint numpnts, Vint numpats)

define number of points and patches

Define the number of points and patches to be defined. Define point coordinates using vis_MapMeshSetPoint() and patch connectivities which reference the input points using vis_MapMeshSetPatch().

Inquire of defined numpnts and numpats as output arguments using

void vis_MapMeshInq (vis_MapMesh *mapmesh,
                     Vint *numpnts,
                     Vint *numpats)

Errors

VIS_ERROR_VALUE is generated if an improper numpnts or numpats is less than or equal to zero.

Parameters
  • p – Pointer to MapMesh object.

  • numpnts – Number of points

  • numpats – Number of paths

void vis_MapMeshInq(vis_MapMesh *p, Vint *numpnts, Vint *numpats)

inquire of defined numpnts and numpats as output arguments

See vis_MapMeshDef()

void vis_MapMeshSetParami(vis_MapMesh *p, Vint ptype, Vint iparam)

set mesh generation parameters

Specify mapped mesh generation parameters. These parameters specify the number and type of finite elements to generate.

The parameter VIS_MESH_LAGRANGE toggles the generation of finite elements with a Lagrange or Serendipity nodal pattern. By default VIS_MESH_LAGRANGE is set to VIS_OFF.

The parameter VIS_MESH_MAXI

sets the order of the generated finite elements by specifying the number of nodes to generate along an edge.

Mapped mesh generation supports linear, parabolic and cubic elements. Mapped mesh generation will only generate elements of equal order in all directions. By default

VIS_MESH_MAXI is set to 2.

Inquire of defined integer parameters as output arguments using

void vis_MapMeshSetParami (vis_MapMesh *mapmesh,
                           Vint ptype,
                           Vint *iparam)

Errors

VIS_ERROR_ENUM is generated if an improper ptype is specified.

Parameters
  • p – Pointer to MapMesh object.

  • ptype – Type of mesh parameter to set

    x=VIS_MESH_LAGRANGE      Nodal pattern of generated elements
     =VIS_MESH_MAXI          Order of generated elements
    

  • iparam – Specifies the integer value that ptype will be set to.

    x=VIS_OFF                Turn parameter off
     =VIS_ON                 Turn parameter on
    

void vis_MapMeshGetParami(vis_MapMesh *p, Vint type, Vint *iparam)

get mesh generation parameters

See vis_MapMeshSetParami()

void vis_MapMeshSetPoint(vis_MapMesh *p, Vint id, Vdouble x[3])

define a point

Set a point location. The point coordinates, x are assumed to be expressed in the basic coordinate system. The basic coordinate system is specified using vis_MapMeshSetCoordSys().

Errors

VIS_ERROR_VALUE is generated if an improper id is specified.

Parameters
  • p – Pointer to MapMesh object.

  • id – Point id

  • x – Point coordinate location

void vis_MapMeshSetPointAssoc(vis_MapMesh *p, Vint type, Vint id, Vint aid)

set a point association

Set a point association. The association is assigned to the node generated at the point. Only an association set at a corner point in a patch is assigned to the generated node. The type of associations allowed are those accepted by the Connect module function vis_ConnectSetNodeAssoc().

Errors

  • VIS_ERROR_ENUM is generated if an improper type is specified.

  • VIS_ERROR_VALUE is generated if an improper id is specified.

Parameters
  • p – Pointer to MapMesh object.

  • type – Type of association

  • id – Point id

  • aid – Association

void vis_MapMeshSetPatch(vis_MapMesh *p, Vint id, Vint shape, Vint maxi, Vint maxj, Vint maxk, Vint pix[])

define parent patch

Specify the topology of a patch and its point connectivity. Note that all patches must be entered sequentially.

Errors

  • VIS_ERROR_ENUM is generated if an improper shape is specified.

  • VIS_ERROR_VALUE is generated if an improper id, maxi, maxj or maxk is specified.

  • VIS_ERROR_OPERATION is generated if an id is entered out of order.

Parameters
  • p – Pointer to MapMesh object.

  • id – Patch id

  • shape – Patch shape parameter

    x=VIS_SHAPELINE          Line
     =VIS_SHAPEQUAD          Quadrilateral
     =VIS_SHAPEHEX           Hexahedron
    

  • maxi – The number of points along the i direction. If maxi = 0 then the linear element form of the specified shape is assumed.

  • maxj – The number of points along the j direction. If maxj = 0 and 2 <= maxi <= 4, then a Serendipity finite element is assumed. If 2 <= maxj and 2 <= maxi, then a Lagrange finite element is assumed. For triangle, tetrahedron and wedge shapes, set either maxj = 0 or maxj = maxi.

  • maxk – The number of points along the k direction. For tetrahedron shapes, set either maxk = 0 or maxk = maxi For hexahedron and wedge shapes, set either maxk = 2 or maxk = maxi

  • pix – Point connectivity of patch.

void vis_MapMeshSetPatchParami(vis_MapMesh *p, Vint id, Vint ptype, Vint iparam)

set a patch parameter

Specify patch parameters for patch id.

The parameter VIS_MESH_SHAPE specifies the shape of generated elements. By default VIS_MESH_SHAPE is set to VIS_SHAPELINE.

The parameters MAPMESH_NUMELEMI, MAPMESH_NUMELEMJ and MAPMESH_NUMELEMK specify the number of elements to generate in the I, J and K directions. By default MAPMESH_NUMELEMI, MAPMESH_NUMELEMJ and MAPMESH_NUMELEMK are set to 1.

Errors

  • VIS_ERROR_ENUM is generated if an improper ptype is specified.

  • VIS_ERROR_VALUE is generated if an improper iparam is specified.

Parameters
  • p – Pointer to MapMesh object.

  • id – Patch id

  • ptype – Type of patch parameter to set

    x=VIS_MESH_SHAPE         Shape of generated elements
     =MAPMESH_NUMELEMI       Number of elements in I direction
     =MAPMESH_NUMELEMJ       Number of elements in J direction
     =MAPMESH_NUMELEMK       Number of elements in K direction
    

  • iparam – Specifies the integer value that ptype will be set to.

    x=VIS_SHAPELINE          Line
     =VIS_SHAPETRI           Triangle
     =VIS_SHAPEQUAD          Quadrilateral
     =VIS_SHAPETET           Tetrahedron
     =VIS_SHAPEPYR           Pyramid
     =VIS_SHAPEWED           Wedge
     =VIS_SHAPEHEX           Hexahedron
    

void vis_MapMeshSetPatchAssoc(vis_MapMesh *p, Vint type, Vint id, Vint enttype, Vint no, Vint assoc)

set parent patch associations

Set a node association for nodes generated along a patch edge or on a patch face or an element association for elements generated within a patch. If enttype is SYS_EDGE then node associations are assigned to all nodes generated on the specified patch edge, no. If enttype is SYS_FACE then node associations are assigned to all nodes generated on the specified patch face, no. If enttype is SYS_ELEM then elements associations are assigned to all elements generated within the specified patch, id. The type of associations allowed are those accepted by the Connect module function vis_ConnectSetNodeAssoc().

Errors

  • VIS_ERROR_ENUM is generated if an improper type or enttype is specified.

  • VIS_ERROR_VALUE is generated if an improper id or no is specified.

Parameters
  • p – Pointer to MapMesh object.

  • type – Type of association

  • id – Patch id

  • enttype – Entity type to which association is applied

    =SYS_EDGE     Patch edge for node association
    =SYS_FACE     Patch face for node association
    =SYS_ELEM     Patch for element association
    

  • no – Patch edge or face number

  • assoc – Association

void vis_MapMeshGenerate(vis_MapMesh *p, vis_Connect *connect)

retrieve status information

Generate nodes and finite elements. The generated nodes and elements are appended to any existing nodes and elements in the input Connect object.

Errors

VIS_ERROR_OPERATION is generated if the patch shape does not allow the generation of the specified element topology.

Parameters
  • p – Pointer to MapMesh object.

  • connect – Pointer to Connect object to receive generated mesh

void vis_MapMeshSetCoordSys(vis_MapMesh *p, vis_CoordSys *coordsys)

define basic coordinate system.

Specify the basic coordinate system as a CoordSys object. The point locations input using vis_MapMeshSetPoint() are assumed to be expressed in the basic coordinate system. All angular coordinates are in degrees. If CoordSys is input as NULL, then the global Cartesian coordinate system is used. By default the basic coordinate system is the global Cartesian coordinate system.

Parameters
  • p – Pointer to MapMesh object.

  • coordsys – Pointer to CoordSys object defining basic coordinate system

void vis_MapMeshGetInteger(vis_MapMesh *p, Vint type, Vint iparam[])

retrieve status information

Query for integer mesh generation information.

The query type VIS_MESH_PROGRESS returns information about the current state of the meshing process. This function is most useful when called from the monitor function. The following four integer values are returned.

 iparam[0]  Meshing phase 
            Phase 1 - Node generation
            Phase 2 - Element generation
            Phase 3 - Cleanup
 iparam[1]  Current number of nodes
 iparam[2]  Current number of elements
 iparam[3]  Estimate percent completion
Errors

VIS_ERROR_ENUM is generated if type is invalid.

Parameters
  • p – Pointer to MapMesh object.

  • type – Type of parameter to be queried

    x=VIS_MESH_PROGRESS       Currently generated parameters
    

  • iparam[out] Values(s) retrieved

2.3. Extruded Mesh Generation - ExtMesh

The ExtMesh module provides for the automatic generation of nodes and elements which are formed by extruding a given cross-section mesh along a given path. The specified cross section mesh can contain any combination of point, line, triangular or quadrilateral elements. These cross section elements are then extruded to form line, quadrilateral, wedge and hexahedral elements respectively. The input cross section elements may be linear or parabolic with Serendipity or Lagrange nodal patterns. The path along which the extrusion is directed may be a connected set of linear, parabolic or cubic lines. The coordinate system in which the path point coordinates are expressed can be changed so that generating finite element nodes extruded in cylindrical or spherical coordinate systems or arbitrarily oriented and positioned coordinate systems is possible. The number of layers of elements generated along each path segment may be specified. An option is also provided to extrude nodal planes along vectors specified at each node of the cross section mesh. This is useful for generating boundary layer meshes.

The functions associated with a ExtMesh object are the following.

Instance an ExtMesh object using vis_ExtMeshBegin(). Once an ExtMesh object is instanced, define the number of nodes and elements which define the cross section mesh using vis_ExtMeshDef(). The cross section mesh is then input as a set of nodes in 3D space and a set of element connectivities. The nodes are defined using vis_ExtMeshSetNode(), the element connectivities are defined using vis_ExtMeshSetElem(). Optional node normals are defined using vis_ExtMeshSetNodeNormal(). Node normals must be defined if extrusion along node normals is enabled. Extrusion path must otherwise be defined with vis_ExtMeshSetPath().

Normal extrusion may be done in multiple layers. Use vis_ExtMeshSetNormalPath() to specify, for each layer, thickness fraction, number of elements through the thickness, and whether a layer of interface elements is to be added.

The user is able to define integer associations at nodes, elements, element edges, and points which will be assigned to the nodes, edges, faces, and elements of the generated entities. These associations are useful for identifying nodes and elements for the application of boundary conditions. Note that the nodes entered using vis_ExtMeshSetNode() appear unchanged in the final mesh. The function vis_ExtMeshSetNodeAssoc() is used to set associations at lines of nodes extruded from specified cross section nodes, The function vis_ExtMeshSetPointAssoc() is used to set associations at nodes generated on nodal planes coincident to a specified point. The node associations are assigned before the point associations at any generated node. The function vis_ExtMeshSetElemAssoc() is used to set edge or element associations at nodes, edges, and faces on the generated entities. Additional associations may be set using the function vis_ExtMeshSetParami(). If the parameters EXTMESH_FACEMARK or EXTMESH_EDGEMARK are set, then if EXTMESH_NORMAL is not enabled, the faces or edges on the original and final cross-sections will have the association defined by the parameters have values of 1 and 2, respectively. If EXTMESH_NORMAL is enabled then the associations defined by the parameters will have values of 1, 2, 3, etc. until one plus the number of paths defined with vis_ExtMeshSetNormalPath().

As an option the cross section mesh may be extruded along normals specified at the cross section nodes. Use the function vis_ExtMeshSetParami() to enable normal extrusion. If normal extrusion is enabled, then extrusion defined by a path is disabled. An important option for use with extrusion along node vectors is a local check to avoid creating inverted elements in areas of high convex curvature. Use the parameter EXTMESH_LOCALRECEDE to enable this option. If the node vectors create inverted elements, the extrusion distance is receded until proper elements result. The distances extruded along neighboring vectors are also receded to create a smoother mesh. The growth rate used to smooth the local recession is set using the function vis_ExtMeshSetParamd() with the parameter EXTMESH_RECEDEGROWTHRATE.

The number of layers of elements to be extruded along each path segment is specified using vis_ExtMeshSetPathParami(). If extrusion along nodal normals is selected, the number of layers is defined by the parameter EXTMESH_NORMAL_NUMLAYERS.

An option also exists when extruding an all quad mesh to generate an all tetrahedral mesh rather than an all hexahedral mesh. Set this option using vis_ExtMeshSetParami() with the parameter EXTMESH_GENTET.

The parameter VIS_MESH_GROWTHRATE can be used to specify a growth rate from one layer to the next. If a path is employed, the growth rate only applies to the first path.

Finally the function vis_ExtMeshGenerate() generates the nodes and finite elements and enters them into a Connect object. The generation process can be monitored or aborted by using vis_ExtMeshSetFunction() to install a monitoring function. If the monitoring function calls vis_ExtMeshAbort() the mesh generation is aborted.

The function vis_ExtMeshWrite() is provided to write a complete description of the defined meshing parameters to a file. The primary use of this file is to encapsulate cases in which the ExtMesh module fails in some respect. This output file can then be made available to Visual Kinematics for failure diagnosis of ExtMesh meshing algorithms.

The following code fragment illustrates the basic framework of using the ExtMesh module to generate linear wedge finite elements extruded along a straight line from a cross section defined by a set of linear triangular elements.

            /* declare objects */
vis_ExtMesh *extmesh;
vis_Connect *connect;
                /* input cross section elements */
Vint numnode, numelem;
Vdouble xnode[][3] = { ... };
Vint ixelem[][3] = { ... };
Vint numpnts, numpats;
Vdouble xpath[2][3] = { ... };
Vint ixpath[2] = { 1,2 };
Vint ierr;

numpnts = 2;
numpats = 1;
                /* create extmesh object */
extmesh = vis_ExtMeshBegin ();
vis_ExtMeshDef (extmesh,numnode);

                /* define cross section nodes and triangle elements */
for (i = 0; i < numnode; i++) {
    vis_ExtMeshSetNode (extmesh,i+1,xnode[i]);
}
for (i = 0; i < numelem; i++) {
    vis_ExtMeshSetElem (extmesh,i+1,VIS_SHAPETRI,maxi,maxj,ixelem[i]);
}
                /* define path points and connectivity */
for (i = 0; i < numpnts; i++) {
    vis_ExtMeshSetPoint (extmesh,i+1,xpath[i]);
}
vis_ExtMeshSetPath (extmesh,2,ixpath);

                /* specify 3 layers of elements */
vis_ExtMeshSetPathParami (extmesh,1,VIS_MESH_NUMELEMENTS,3);

                /* create empty connect object to hold generated mesh */
connect = vis_ConnectBegin ();
vis_ConnectDef (connect,0,0);

                /* generate mesh */
vis_ExtMeshGenerate (extmesh,connect);

                /* process any errors */
ierr = vis_ExtMeshError (extmesh);
if(ierr) {
    ...
}
                /* access generated nodes and elements from Connect */
...
                /* delete objects */
vis_ConnectEnd (connect);
vis_ExtMeshEnd (extmesh);

2.4. Function Descriptions

The currently available ExtMesh functions are described in detail in this section.

vis_ExtMesh *vis_ExtMeshBegin(void)

create an instance of an ExtMesh object

Create an instance of an ExtMesh object. Memory is allocated for the object private data and the pointer to the data is returned.

Destroy an instance of a ExtMesh object using

void vis_ExtMeshEnd (vis_ExtMesh *extmesh)

Return the current value of a ExtMesh object error flag using

Vint vis_ExtMeshError (vis_ExtMesh *extmesh)

Returns

The function returns a pointer to the newly created ExtMesh object. If the object creation fails, NULL is returned.

void vis_ExtMeshEnd(vis_ExtMesh *p)

destroy an instance of an ExtMesh object

See vis_ExtMeshBegin()

Vint vis_ExtMeshError(vis_ExtMesh *p)

return the current value of an ExtMesh object error flag

See vis_ExtMeshBegin()

void vis_ExtMeshDef(vis_ExtMesh *p, Vint numnode, Vint numelem)

define number of section nodes, elements

Define the number of nodes and elements which define the input cross section mesh. Define node coordinates using vis_ExtMeshSetNode() and optional node normals using vis_ExtMeshSetNodeNormal(). Define element topology and connectivities using vis_ExtMeshSetElem().

Define point coordinates using vis_ExtMeshSetPoint() and path connectivities which reference the input points using vis_ExtMeshSetPath().

Inquire of defined numnode, numelem as output arguments using

void vis_ExtMeshInq (vis_ExtMesh *extmesh,
                     Vint *numnode,
                     Vint *numelem)

Errors

VIS_ERROR_VALUE is generated if numnode, or numelem is less than or equal to zero.

Parameters
  • p – Pointer to ExtMesh object.

  • numnode – Number of nodes on cross section mesh

  • numelem – Number of elements on cross section mesh

void vis_ExtMeshInq(vis_ExtMesh *p, Vint *numnode, Vint *numelem)

inquire of defined numnode, numelem as output arguments

See vis_ExtMeshDef()

void vis_ExtMeshSetParami(vis_ExtMesh *p, Vint ptype, Vint iparam)

set mesh generation parameters

Specify mesh generation parameters.

The parameter EXTMESH_NORMAL enables the extrusion of the cross section mesh along node normals specified by vis_ExtMeshSetNodeNormal(). If this parameter is set to SYS_ON extrusion through a path is disabled. The magnitude of these normal vectors indicate the distance each node is extruded. By default EXTMESH_NORMAL is set to SYS_OFF.

The parameter EXTMESH_ELEMMARK specifies the association type that will be used to tag all elements belonging to a normal path. The association values on those elements will be 1 on the first path, 2 on the second path, and so on. These associations can be retrieved from the resulting Connect module with vis_ConnectElemAssoc(). By default these associations are not set.

The parameter EXTMESH_FACEMARK specifies the association type that will be used to tag the faces on the first and last extrusion planes. The association values on those faces will be 1 and 2 on the first and last extrusion planes, respectively. These associations can be retrieved from the resulting Connect module with vis_ConnectAllElemEntAssoc() with entity type set to SYS_FACE. By default these associations are not set.

The parameter EXTMESH_EDGEMARK specifies the association type that will be used to tag the edges on the first and last extrusion planes. The association values on those edges will be 1 and 2 on the first and last extrusion planes, respectively. These associations can be retrieved from the resulting Connect module with vis_ConnectAllElemEntAssoc() with entity type set to SYS_EDGE. By default these associations are not set.

The parameter EXTMESH_GLOBALRECEDE toggles the global checking of front intersection and enabling the recession of the extrusion distance. By default EXTMESH_GLOBALRECEDE is set to SYS_OFF.

The parameter EXTMESH_LOCALRECEDE toggles the local checking of element inversion and enabling the recession of the extrusion distance. By default EXTMESH_LOCALRECEDE is set to SYS_OFF.

The parameter EXTMESH_GENTET toggles the generation of tetrahedron elements for pentahedron elements when extruding all triangle surfaces. By default EXTMESH_GENTET is set to SYS_OFF.

The parameter EXTMESH_REVERSE toggles the sense of the element connectivity generated during extrusion. This option is useful when generating boundary layer extrusions into the interior of a geometry defined by a surface mesh whose connectivty sense points to the exterior of the geometry. By default EXTMESH_REVERSE is set to SYS_OFF.

The parameter EXTMESH_SMOOTHMISIDE toggles the interpolation of the normal vector at the midside nodes. By default EXTMESH_SMOOTHMIDSIDE is set to SYS_ON.

Inquire of defined integer parameters as output arguments using

void vis_ExtMeshSetParami (vis_ExtMesh *extmesh,
                           Vint ptype,
                           Vint *iparam)

Errors

VIS_ERROR_ENUM is generated if an improper ptype is specified, or if its corresponding iparam value is invalid.

Parameters
  • p – Pointer to ExtMesh object.

  • ptype – Type of mesh parameter to set

    x=EXTMESH_EDGEMARK         Extrusion plane edge associations
     =EXTMESH_ELEMMARK         Normal path element associations
     =EXTMESH_FACEMARK         Extrusion plane face associations
     =EXTMESH_GENTET           Create all tet elements
     =EXTMESH_GLOBALRECEDE     Toggle front intersection check
     =EXTMESH_LOCALRECEDE      Toggle local element inversion check
     =EXTMESH_NORMAL           Enable extrusion along node normals
     =EXTMESH_REVERSE          Toggle element connectivity sense
     =EXTMESH_SMOOTHMIDSIDE    Toggle normal vector interpolation at midside nodes
    

  • iparam – Specifies the integer value that ptype will be set to.

void vis_ExtMeshGetParami(vis_ExtMesh *p, Vint type, Vint *iparam)

get mesh generation parameters

See vis_ExtMeshSetParami()

void vis_ExtMeshSetParamd(vis_ExtMesh *p, Vint ptype, Vdouble dparam)

set mesh generation parameters

Specify mesh generation parameters. These parameters are used to control the size of the generated elements.

The parameter VIS_MESH_GROWTHRATE specifies a growth rate for the extruded size of element layers. If path extrusion is selected, then the growth rate is only applied to the extrusion defined by the first path. For second and subsequent paths the growth rate is unity. By default VIS_MESH_GROWTHRATE is set to unity.

The parameter VIS_MESH_RECEDEGROWTHRATE specifies a growth rate for the smoothing of local distance recession which may optionally occur when extruding along node vectors. By default VIS_MESH_RECEDEGROWTHRATE is set to 1.5.

Inquire of defined double precision parameters as output arguments using

void vis_ExtMeshSetParamd (vis_ExtMesh *extmesh,
                           Vint ptype,
                           Vdouble *dparam)

Errors

  • VIS_ERROR_ENUM is generated if an improper ptype is specified.

  • VIS_ERROR_VALUE is generated if an improper growth rate is specified.

Parameters
  • p – Pointer to ExtMesh object.

  • ptype – Type of mesh parameter to set

    x=VISMESH_GROWTHRATE         Growth rate
     =EXTMESH_RECEDEGROWTHRATE   Recession Growth rate
    

  • dparam – Specifies the value that ptype will be set to.

void vis_ExtMeshGetParamd(vis_ExtMesh *p, Vint type, Vdouble *dparam)

get mesh generation parameters

See vis_ExtMeshSetParamd()

void vis_ExtMeshSetNode(vis_ExtMesh *p, Vint id, Vdouble x[3])

define a node

Set a node location. The node id must be in the interval 1 <= id <= numnode where numnode is defined by vis_ExtMeshDef(). The coordinates, x, are always in the global coordinate system. Element connectivity is defined using vis_ExtMeshSetElem().

Errors

VIS_ERROR_VALUE is generated if an improper id is specified.

Parameters
  • p – Pointer to ExtMesh object.

  • id – Node id

  • x – Node coordinate location

void vis_ExtMeshSetNodeNormal(vis_ExtMesh *p, Vint id, Vdouble v[3])

define a node normal

Set a node normal v. The node id must be in the interval 1 <= id <= numnode where numnode is defined by vis_ExtMeshDef(). The node normal is used as an extrusion direction if the EXTMESH_NORMAL option is enabled using vis_ExtMeshSetParami(). The distance along the length of the normal vector is added to the extrusion for each path. Therefore the direction and length of the normal vector determine the extrusion distance.

Errors

VIS_ERROR_VALUE is generated if an improper id is specified

Parameters
  • p – Pointer to ExtMesh object.

  • id – Node id

  • v – Node normal

void vis_ExtMeshSetNodeAssoc(vis_ExtMesh *p, Vint type, Vint id, Vint aid)

set a node association

Set a node association. The association is assigned to all nodes and edges generated along the line of nodes extruded from the corresponding node id. Node asssociations in the resulting Connect module can be retrieved with vis_ConnectAllNodeAssoc(), while edge associations can be retrieved with vis_ConnectAllElemEntAssoc(), where the entity type is SYS_EDGE. The type of associations allowed are those accepted by the Connect module function vis_ConnectSetNodeAssoc(). Use vis_ExtMeshSetPointAssoc() to set associations to be assigned at planes of nodes.

Errors

  • VIS_ERROR_ENUM is generated if an improper type is specified.

  • VIS_ERROR_VALUE is generated if an improper id is specified.

Parameters
  • p – Pointer to ExtMesh object.

  • type – Type of association

  • id – Node id

  • aid – Node association

void vis_ExtMeshSetElem(vis_ExtMesh *p, Vint id, Vint shape, Vint maxi, Vint maxj, Vint ix[])

define an element connectivity

Set an element connectivity. The element id must be in the interval 1 <= id <= numelem where numelem is defined by vis_ExtMeshDef(). The element connectivity, ix, must contain the number of points corresponding to the specified shape, maxi, and maxj values used. Only linear and parabolic elements are supported. Note that all elements must be entered sequentially.

Errors

  • VIS_ERROR_VALUE is generated if an improper id is specified.

  • VIS_ERROR_ENUM is generated if an improper shape is specified.

  • VIS_ERROR_OPERATION is generated if an id is entered out of order.

Parameters
  • p – Pointer to ExtMesh object.

  • id – Element id

  • shape – Element shape

    x=VIS_SHAPEPOINT         Point
     =VIS_SHAPELINE          Line
     =VIS_SHAPETRI           Triangle
     =VIS_SHAPEQUAD          Quadrilateral
    

  • maxi – The number of points along the i direction. If maxi = 0 then the linear element form of the specified shape is assumed.

  • maxj – The number of points along the j direction. If maxj = 0 and 2 <= maxi <= 3, then a Serendipity finite element is assumed. If 2 <= maxj and 2 <= maxi, then a Lagrange finite element is assumed. For triangle set either maxj = 0 or maxj = maxi.

  • ix – Element connectivity

void vis_ExtMeshSetElemAssoc(vis_ExtMesh *p, Vint type, Vint id, Vint enttype, Vint no, Vint aid)

define an element association

Set an element association. The element id must be in the interval 1 <= id <= numelem where numelem is defined by vis_ExtMeshDef(). no must be a number between 1 and 4. If an invalid edge number within this range is specified for the specific element then this association will be be ignored in vis_ExtMeshGenerate(). The association value aid must be greater than zero.

SYS_EDGE associations are assigned to all faces extruded from an edge. SYS_ELEM associations are assigned to all elements extruded from an element.

Errors

  • VIS_ERROR_VALUE is generated if an improper id or no is specified.

  • VIS_ERROR_ENUM is generated if an improper type or enttype is specified.

Parameters
  • p – Pointer to ExtMesh object.

  • type – Type of element association

  • enttype – Type of element entity

    x=SYS_EDGE         Element edge
     =SYS_ELEM         Element
    

  • id – Element id

  • no – Element edge number

  • aid – Element association value

void vis_ExtMeshSetPoint(vis_ExtMesh *p, Vint id, Vdouble x[3])

define a path point

Set a path point location. The point id must be in the interval 1 <= id <= numpnts where numpnts is defined by vis_ExtMeshDef(). Input paths are defined using vis_ExtMeshSetPath().

Errors

VIS_ERROR_VALUE is generated if an improper id is specified.

Parameters
  • p – Pointer to ExtMesh object.

  • id – Point id

  • x – Point coordinate location

void vis_ExtMeshSetPointAssoc(vis_ExtMesh *p, Vint type, Vint id, Vint aid)

set a point association

Set a point association. The association is assigned to all nodes generated on a plane of nodes corresponding to the point. Only an association set at a start or end point of the path is assigned to the generated nodes. The type of associations allowed are those accepted by the Connect module function vis_ConnectSetNodeAssoc().

Errors

  • VIS_ERROR_ENUM is generated if an improper type is specified.

  • VIS_ERROR_VALUE is generated if an improper id is specified.

Parameters
  • p – Pointer to ExtMesh object.

  • type – Type of association

  • id – Point id

  • aid – Point association

void vis_ExtMeshSetNormalPath(vis_ExtMesh *p, Vint numlayers, Vdouble fraction, Vint interflag)

set layer parameter for normal extrusion

Multiple layers may be generated to cover the required thickness. This function should be called once for each laminar extrusion. fraction values need not add up to 1., all values of fraction will be scaled by a uniform factor such that their sum adds up to 1. Interface elements are added for each laminar extrusion for which interflag is set to SYS_ON. If either integer parameters EXTMESH_EDGEMARK or EXTMESH_FACEMARK are set then that association is set in incremental value starting at 1 for each normal path defined.

Errors

VIS_ERROR_VALUE is generated if a improper values of numlayers or fraction are specified

Parameters
  • p – Pointer to ExtMesh object.

  • numlayers – Number of extruded layers for given fraction

  • fraction – Fraction of total thickness to be extruded

  • interflag – Toggle for generating a layer of interface elements

void vis_ExtMeshSetPath(vis_ExtMesh *p, Vint maxi, Vint pix[])

define a path connectivity

Set a path connectivity. The path connectivity, pix, must contain maxi points. The value of maxi determines the order of the Lagrange polynomial used to define the path. Use vis_ExtMeshSetPathParami() to specify the number of element layers to be generated along a given path.

When called more than once, this function requires that the path be ordered, i.e., the first point defined on a new call to the function must equal the last point in the previous call.

An internal path id is assigned to each path as it is defined, starting from 1. This id is used in vis_ExtMeshSetPathParami().

Errors

  • VIS_ERROR_VALUE is generated if an improper maxi is specified.

  • VIS_ERROR_OPERATION is generated if the first point in a new path is not equal to the last node in the previous path.

Parameters
  • p – Pointer to ExtMesh object.

  • maxi – Number of points in path, 2 <= maxi <= 4

  • pix – Path connectivity

void vis_ExtMeshSetPathParami(vis_ExtMesh *p, Vint id, Vint ptype, Vint iparam)

define a path paramter

Specify path parameters for path id.

The parameter VIS_MESH_NUMELEMENTS specifies the number of layers of elements to be generated along path id. By default VIS_MESH_NUMELEMENTS is set to 1.

Errors

  • VIS_ERROR_ENUM is generated if an improper ptype is specified.

  • VIS_ERROR_VALUE is generated if an improper iparam is specified.

Parameters
  • p – Pointer to ExtMesh object.

  • id – Path id

  • ptype – Type of path parameter to set

    x=VIS_MESH_NUMELEMENTS   Number of element layers
    

  • iparam – Specifies the integer value that ptype will be set to.

void vis_ExtMeshSetOriginTriad(vis_ExtMesh *p, Vint type, Vdouble x[3], Vdouble tm[3][3])

define a basic coordinate system.

Specify the type, the coordinate system origin, x in global coordinates, and the system orientation, tm. The direction cosine matrix, tm, should be a proper orthonormal rotation matrix. No check is performed on the validity of the input tm. By default the basic coordinate system is the global Cartesian coordinate system. Use a cylindrical coordinate system, for example, to sweep cross section meshes as a body of revolution.

Node coordinates input using vis_ExtMeshSetNode() are always in the global coordinate system. All nodes generated by vis_ExtMeshGenerate() are also in the global coordinates system.

Errors

VIS_ERROR_ENUM is generated if an improper type is specified.

Parameters
  • p – Pointer to ExtMesh object.

  • type – Coordinate system type.

    x=SYS_CARTESIAN       Cartesian system
     =SYS_CYLINDRICAL     Cylindrical system
     =SYS_CYLINDRICAL_ALT Cylindrical alternate system
     =SYS_SPHERICAL       Spherical system
     =SYS_SPHERICAL_ALT   Spherical alternate system
    

  • x – Origin of coordinate system in global coordinates.

  • tm – Direction cosine matrix of system local axis.

void vis_ExtMeshGenerate(vis_ExtMesh *p, vis_Connect *connect)

generate finite element mesh

Generate extruded nodes and finite elements. The input Connect object is cleared of its contents and the generated nodes and elements are set in it. Upon completion, all generated nodes are in the global coordinate system.

Errors

VIS_ERROR_OPERATION is generated if mesh generation fails due to errors detected in the cross section mesh; or if a nodal normal extrusion is requested as a node has been detected with an undefined normal; or the default path extrusion is requested and no paths have been defined.

Parameters
  • p – Pointer to ExtMesh object.

  • connect – Pointer to Connect object to receive generated mesh

void vis_ExtMeshSetFunction(vis_ExtMesh *p, Vint functype, Vfunc *function, Vobject *object)

set a function pointer

Set a pointer to a function. By default, the monotir callback is NULL. A callback is not invoked if it is NULL.

The methods vis_ExtMeshAbort() and vis_ExtMeshGetInteger()` can be called from within the monitoring function if necessary. The first aborts the mesh generation, while the second provides information on its status.

Errors

VIS_ERROR_ENUM is generated if an improper functype is specified.

Parameters
  • p – Pointer to ExtMesh object.

  • functype – The function type identifier

    x=SYS_FUNCTION_MONITOR         Monitoring function
    

  • function – Pointer to the function to be called

  • object – Pointer to a user object to be passed to the monitoring function

void vis_ExtMeshAbort(vis_ExtMesh *p)

abort the mesh generation

Aborts the mesh generation process initiated with vis_ExtMeshGenerate(). This function is usually called from within a user-defined monitoring function specified with vis_ExtMeshSetFunction(). The monitoring function is called at regular intervals during mesh generation, thereby allowing the user to issue the abort command if necessary.

Parameters

p – Pointer to ExtMesh object.

void vis_ExtMeshWrite(vis_ExtMesh *p, Vint type, const Vchar *path)

write mesh description to file

Write a mesh description to a file which has been input to ExtMesh. The contents of the file is intended for internal use only. This function should be called after all input and meshing parameters have been set to ensure that an accurate mesh description including correct meshing parameters is written. The binary file format is preferred for accuracy and generally results in smaller file sizes. The primary use of this function is to create a file of the complete mesh description in the case that the ExtMesh module fails to properly generate a mesh. This file can then be transmitted to Visual Kinematics for debugging purposes. It is suggested that a file extension of .ext be used for ASCII files and .bext be used for BINARY files.

Errors

  • SYS_ERROR_ENUM is generated if an improper type is specified.

  • SYS_ERROR_FILE is generated if the file can not be opened.

  • SYS_ERROR_OPERATION is generated if the input mesh has not been defined.

Parameters
  • p – Pointer to ExtMesh object.

  • type – File type

    x=SYS_ASCII              ASCII format
     =SYS_BINARY             Binary format
    

  • path[out] File path

void vis_ExtMeshRead(vis_ExtMesh *p, Vint type, const Vchar *path)

read mesh description from file

Read a mesh description from a file which has been previously written by vis_ExtMeshWrite(). The format of the file is not published and is intended for internal use only.

Errors

  • SYS_ERROR_ENUM is generated if an improper type is specified.

  • SYS_ERROR_FILE is generated if the file can not be opened.

  • SYS_ERROR_FORMAT is generated if the file contents are not correctly formatted or if a file written by a later version of ExtMesh is read.

Parameters
  • p – Pointer to ExtMesh object.

  • type – mesh description from file

    x=SYS_ASCII              ASCII format
     =SYS_BINARY             Binary format
    

  • path – File path

void vis_ExtMeshGetInteger(vis_ExtMesh *p, Vint type, Vint iparam[])

retrieve status information

Query for integer mesh generation information.

The query type EXTMESH_NUMINTERSECT returns the number of input elements which intersect. The query EXTMESH_INTERSECT will return the list of intersecting elements.

The query type VIS_MESH_PROGRESS returns information about the current state of the meshing process. This function is most useful when called from the monitor function. The following four integer values are returned.

iparam[0]   Meshing phase
            Phase 1 - Pre-processing boundary data
            Phase 2 - Generating interior points
iparam[1]   Current number of nodes
iparam[2]   Current number of elements
iparam[3]   Estimate percent completion
Errors

VIS_ERROR_ENUM is generated if type is invalid.

Parameters
  • p – Pointer to ExtMesh object.

  • type – Type of parameter to be queried

    x=VIS_MESH_PROGRESS       Currently generated parameters
     =EXTMESH_NUMINTERSECT    Number of intersecting elements
     =EXTMESH_INTERSECT       Intersecting elements
    

  • iparam[out] Values(s) retrieved