EDA Mesh Topology

From DocR21

Both surface and volumetric meshes are represented by a set of nodes and a set of elements containing faces and edges. The faces and edges are described as lists of indices into the nodes array for the entire mesh. Control of mesh properties is handled through the mesh options arguments to the mesh generation functions with the va_surface_mesh_options and va_tet_mesh_options objects.

Contents 1 Topology 1.1 Surface Mesh Elements 1.2 Volumetric Mesh Elements 2 Mesh Order 3 Element Types 3.1 VA_SURFACE_TRI_LINEAR 3.2 VA_SURFACE_TRI_PARABOLIC 3.3 VA_SURFACE_TRI_LAGRANGE 3.4 VA_SURFACE_QUAD_LINEAR 3.5 VA_SURFACE_QUAD_PARABOLIC 3.6 VA_SURFACE_QUAD_LAGRANGE 3.7 VA_TET_LINEAR 3.8 VA_TET_PARABOLIC 3.9 VA_TET_LAGRANGE

Topology

See also: EDA Querying

The node array for a mesh is an indexed array with the indices starting at 1. The positions of sets of nodes may be queried with api_va_get_node_positions.

All elements in a mesh are represented by an ID, which is also 1 based. api_va_get_element_data is used to query information about an element in the mesh; the sections below describe the faces and edges depending on the type of the element.

Surface Mesh Elements

For surface meshes there is one face in each element. Both Triangular and Quadrilateral faces are supported through the va_surface_mesh_options parameter to the mesh generation function api_va_generate_surface_mesh.

Volumetric Mesh Elements

For volumetric meshes, only tetrahedral meshes are supported in which there are four triangular faces in each element. The tetrahedral meshes may only be generated from triangulated surface meshes, so internally api_va_generate_tet_mesh creates a triangular surface mesh if called with ACIS ENTITYs to convert. If a surface mesh is used as input then it cannot be made up of quadrilateral elements.

Mesh Order

Linear or Parabolic output meshes are supported through the va_surface_mesh_options argument to the generation functions.

Element Types

Once a mesh has been generated, the elements may be queried for information using api_va_get_element_data which will return the type of the element as VA_ELEMENT_TYPE, the number of faces in the element, the number of edges in the element, the number of nodes in the element and the actual node indices within the mesh. To get information about the node positions, use api_va_get_node_positions. Refer to the following table for an explanation of each of the types that may be returned:

Table. Mesh Element Types, Representation, and Connectivity

Element Type	Representation	Connectivity
VA_SURFACE_TRI_LINEAR	Linear Surface Mesh, Triangular Elements	face_count edge_count node_count faces edges 1 3 3 0,1,2 0,1 1,2 2,0
VA_SURFACE_TRI_PARABOLIC	Linear Surface Mesh, Triangular Elements	face_count edge_count node_count faces edges 1 3 6 0,1,2 0,1 1,2 2,0 Note that nodes 3,4,5 are intermediate points on the edges.
VA_SURFACE_TRI_LAGRANGE	Surface Mesh, Triangular Elements, Lagrange Connectivity	For a description of Lagrange elements, refer to the VKI documentation.
VA_SURFACE_QUAD_LINEAR	Linear Surface Mesh, Triangular Elements	face_count edge_count node_count faces edges 1 4 4 0,1,2,3 0,1 1,2 2,3 3,0
VA_SURFACE_QUAD_PARABOLIC	Parabolic Surface Mesh, Quadrilateral Elements	face_count edge_count node_count faces edges 1 4 4 0,1,2,3 0,1 1,2 2,3 3,0 Note that nodes 4,5,6,7 are intermediate points on the edges.
VA_SURFACE_QUAD_LAGRANGE	Surface Mesh, Quadrilateral Elements, Lagrange Connectivity	For a description of Lagrange elements, refer to the VKI documentation.
VA_TET_LINEAR	Linear Tetrahedral Mesh, Triangular Elements	face_count edge_count node_count faces edges 4 6 6 0,2,1 0,1,3 0,3,2 1,2,3 0,1 1,2 2,0 0,3 1,3 2,3
VA_TET_PARABOLIC	Parabolic Tetrahedral Mesh, Triangular Elements	face_count edge_count node_count faces edges 4 6 6 0,2,1 0,1,3 0,3,2 1,2,3 0,1 1,2 2,0 0,3 1,3 2,3 Note that nodes 4,5,6,7,8,9 are intermediate points on the edges.
VA_TET_LAGRANGE	Tetrahedral Mesh, Triangular Elements, Lagrange Connectivity	For a description of Lagrange elements, refer to the VKI documentation.