AMCAX Kernel 1.0.0.0
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Example of Virtual Topology Composite Function

Overview

This tutorial provides detailed usage of various geometric composite functions in virtual topology for ignoring minor geometries such as short edges/narrow faces in geometric models.

Functional Description

Composite Edges

Select multiple adjacent edges to combine, returning a new composite edge. The new edge's Tag is the original number of edges in the model plus 1. The original edges are retained but disabled in the model and can be removed via remove operations.

Composite Faces

Select multiple adjacent faces to combine, returning a new composite face. The new face's Tag is the original number of faces in the model plus 1. The original faces are retained but disabled in the model and can be removed via remove operations.

Composite Solids

Select multiple adjacent solids to combine, returning a new composite solid. The new solid's Tag is the original number of solids in the model plus 1. The original solids are retained but disabled in the model and can be removed via remove operations.

Interface Description

Interfaces

AddCompositeEntity

Composite edges, composite faces, and composite solids all use the AddCompositeEntity interface uniformly.

RemoveEntities

Remove composite edges, composite faces, and composite solids all use the RemoveEntities interface. Supports simultaneous removal of any combination of edges, faces, and solids, as well as any composite geometric elements. The removal operation will sequentially remove all geometric elements that have been composited with the target element. For example: FaceA and FaceB are composited into FaceC, FaceC and FaceD are composited into FaceE. When removing FaceC, both FaceE and FaceC will be removed.

Parameter Description

  • Parameter std::vector<NMEntity> &entities represents the entities to be composited. The entities must have consistent dimensions and be adjacent (i.e., 1D can form connected edges, 2D can form connected regions, 3D can form connected composite solids).
  • Parameter bool ignoreAdjSubEntity = true indicates whether to ignore adjacent sub-entities, default is true. This parameter has no effect for composite edges. For composite faces, it will ignore adjacent points. For composite solids, it will ignore adjacent edges and points.

Input Requirements

  • Input entities must have consistent dimensions and be mutually adjacent.
  • After composition, dangling nodes must be avoided (composite edges: internal points of the composite edge must not have degrees other than 2; composite faces: internal edges of the connected region must not have degrees other than 2; composite solids: not applicable). Taking composite edges as an example (composite faces are similar): the left image shows that composition would produce dangling edges, which is not allowed; the right image shows that composition would not produce dangling edges, which is allowed.

Composite Operations

Composite Edges

The model has short edge features, which are preserved when meshing edge grids.


const std::string cadstr = "./data/zhijiav1.brep";
const std::string jsonPath = "./data/param.json";
NMAPIModel nmapi;
NMAPIModel::InitLogger();
AMCAX::TopoShape shape;
OCCTIO::OCCTTool::Read(shape, cadstr);
nmapi.ImportModel({ shape });
std::vector<NMEntity> composite_entitys_D1;
composite_entitys_D1.push_back(nmapi.GetEntity(DimType::D1, 210));
composite_entitys_D1.push_back(nmapi.GetEntity(DimType::D1, 211));
auto cpD1 = nmapi.AddCompositeEntity(composite_entitys_D1);
nlohmann::json paraJ = nlohmann::json::parse(std::ifstream(jsonPath));
paraJ["MeshSize"][0]["MeshingDim"] = 1;
paraJ["MeshSize"][0]["SelectedEntities"][0] = nmapi.EntityGetTag(cpD1);
nmapi.GenerateMesh(paraJ.dump());
auto meshapi = nmapi.GetMesh();
AMCAX::TopoShape
Base class of shape, containing an underlying shape with a location and an orientation.
Definition TopoShape.hpp:15

After compositing short edges, they disappear when meshing edge grids.

Click here example07 to get the full source code of the composite edge example. Everyone can download it as needed.

Composite Faces

The model has multiple narrow faces, which are preserved when meshing face grids.


const std::string cadstr = "./data/zhijiav1.brep";
const std::string jsonPath = "./data/param.json";
NMAPIModel nmapi;
NMAPIModel::InitLogger();
AMCAX::TopoShape shape;
OCCTIO::OCCTTool::Read(shape, cadstr);
nmapi.ImportModel({ shape });
std::vector<NMEntity> composite_entitys_D2;
composite_entitys_D2.push_back(nmapi.GetEntity(DimType::D2, 66));
composite_entitys_D2.push_back(nmapi.GetEntity(DimType::D2, 67));
composite_entitys_D2.push_back(nmapi.GetEntity(DimType::D2, 68));
composite_entitys_D2.push_back(nmapi.GetEntity(DimType::D2, 69));
composite_entitys_D2.push_back(nmapi.GetEntity(DimType::D2, 70));
composite_entitys_D2.push_back(nmapi.GetEntity(DimType::D2, 71));
composite_entitys_D2.push_back(nmapi.GetEntity(DimType::D2, 79));
composite_entitys_D2.push_back(nmapi.GetEntity(DimType::D2, 80));
composite_entitys_D2.push_back(nmapi.GetEntity(DimType::D2, 81));
composite_entitys_D2.push_back(nmapi.GetEntity(DimType::D2, 86));
composite_entitys_D2.push_back(nmapi.GetEntity(DimType::D2, 87));
composite_entitys_D2.push_back(nmapi.GetEntity(DimType::D2, 90));
auto cpD2 = nmapi.AddCompositeEntity(composite_entitys_D2);
nlohmann::json paraJ = nlohmann::json::parse(std::ifstream(jsonPath));
paraJ["MeshSize"][0]["MeshingDim"] = 2;
paraJ["MeshSize"][0]["SelectedEntities"][0] = nmapi.EntityGetTag(cpD2);
nmapi.GenerateMesh(paraJ.dump());
auto meshapi = nmapi.GetMesh();

After compositing narrow faces, they disappear when meshing face grids.

Click here example08 to get the full source code of the composite face example. Everyone can download it as needed.

Composite Solids

In the left figure, tetrahedral meshing is performed on two volume elements, and the intersecting face features are retained. In the right figure, the selected volumes are combined, and the intersecting face features disappear.


const std::string cadstr = "./data/imprint.brep";
const std::string jsonPath = "./data/param.json";
NMAPIModel nmapi;
NMAPIModel::InitLogger();
TopoShape shape;
OCCTIO::OCCTTool::Read(shape, cadstr);
nmapi.ImportModel({ shape });
std::vector<NMEntity> composite_entitys_D3;
composite_entitys_D3.push_back(nmapi.GetEntity(DimType::D3, 1));
composite_entitys_D3.push_back(nmapi.GetEntity(DimType::D3, 2));
auto cpD3 = nmapi.AddCompositeEntity(composite_entitys_D3, false);
nlohmann::json paraJ = nlohmann::json::parse(std::ifstream(jsonPath));
paraJ["MeshSize"][0]["MeshingDim"] = 3;
paraJ["MeshSize"][0]["SelectedEntities"][0] = nmapi.EntityGetTag(cpD3);
nmapi.GenerateMesh(paraJ.dump());
auto meshapi = nmapi.GetMesh();

Click here example09 to get the full source code of the composite solid example. Everyone can download it as needed.

Complete Example

The following is a complete example demonstrating how to call the composite function API for multiple nested composites, including the method of removing composite geometric elements.

#include <nextmesh/NMAPIModel.hpp>
#include <nlohmann/json.hpp>
#include<occtio/OCCTTool.hpp>
#include <fstream>
using namespace AMCAX::NextMesh;
using namespace AMCAX;
int main()
{
const std::string cadstr = "./data/zhijiav1.brep";
const std::string jsonPath = "./data/param.json";
NMAPIModel nmapi;
NMAPIModel::InitLogger();
TopoShape shape;
OCCTIO::OCCTTool::Read(shape, cadstr);
nmapi.ImportModel({ shape });
// Composite edges
std::vector<NMEntity> composite_entitys_D11;
composite_entitys_D11.push_back(nmapi.GetEntity(DimType::D1, 210));
composite_entitys_D11.push_back(nmapi.GetEntity(DimType::D1, 211));
auto cpD11 = nmapi.AddCompositeEntity(composite_entitys_D11);
// Composite faces
std::vector<NMEntity> composite_entitys_D21;
composite_entitys_D21.push_back(nmapi.GetEntity(DimType::D2, 66));
composite_entitys_D21.push_back(nmapi.GetEntity(DimType::D2, 67));
composite_entitys_D21.push_back(nmapi.GetEntity(DimType::D2, 68));
composite_entitys_D21.push_back(nmapi.GetEntity(DimType::D2, 69));
composite_entitys_D21.push_back(nmapi.GetEntity(DimType::D2, 70));
composite_entitys_D21.push_back(nmapi.GetEntity(DimType::D2, 71));
composite_entitys_D21.push_back(nmapi.GetEntity(DimType::D2, 79));
composite_entitys_D21.push_back(nmapi.GetEntity(DimType::D2, 80));
composite_entitys_D21.push_back(nmapi.GetEntity(DimType::D2, 81));
composite_entitys_D21.push_back(nmapi.GetEntity(DimType::D2, 86));
composite_entitys_D21.push_back(nmapi.GetEntity(DimType::D2, 87));
composite_entitys_D21.push_back(nmapi.GetEntity(DimType::D2, 90));
auto cpD21 = nmapi.AddCompositeEntity(composite_entitys_D21, false);
// Composite edges
std::vector<NMEntity> composite_entitys_D12;
composite_entitys_D12.push_back(nmapi.GetEntity(DimType::D1, 157));
composite_entitys_D12.push_back(nmapi.GetEntity(DimType::D1, 158));
auto cpD12 = nmapi.AddCompositeEntity(composite_entitys_D12);
// Composite faces
std::vector<NMEntity> composite_entitys_D22;
composite_entitys_D22.push_back(nmapi.GetEntity(DimType::D2, 33));
composite_entitys_D22.push_back(nmapi.GetEntity(DimType::D2, 34));
composite_entitys_D22.push_back(nmapi.GetEntity(DimType::D2, 35));
composite_entitys_D22.push_back(nmapi.GetEntity(DimType::D2, 36));
auto cpD22 = nmapi.AddCompositeEntity(composite_entitys_D22);
// Composite faces
std::vector<NMEntity> composite_entitys_D23;
composite_entitys_D23.push_back(cpD21);
composite_entitys_D23.push_back(cpD22);
auto cpD23 = nmapi.AddCompositeEntity(composite_entitys_D23);
// remove comosite entity
/*
std::vector<NMEntity> remove_entitys;
remove_entitys.push_back(cpD11);
remove_entitys.push_back(cpD21);
remove_entitys.push_back(cpD12);
remove_entitys.push_back(cpD22);
remove_entitys.push_back(cpD23);
nmapi.RemoveEntities(remove_entitys);
*/
nlohmann::json paraJ = nlohmann::json::parse(std::ifstream(jsonPath));
paraJ["MeshSize"][0]["SelectedEntities"][0] = nmapi.EntityGetTag(cpD23);
nmapi.GenerateMesh(paraJ.dump());
auto meshapi = nmapi.GetMesh();
OutParams outp{};
meshapi.Write("./zhijiav1.obj", OutFileType::OBJ, outp);
}
NMAPIModel.hpp
Class of NextMesh Model.
OCCTTool.hpp
Class of read and write shapes from OCCT BRep files.
AMCAX::NextMesh::NMAPIModel
Class of model in NextMesh.
Definition NMAPIModel.hpp:22
AMCAX::NextMesh::NMAPIModel::ImportModel
AMCAX_API void ImportModel(const std::vector< NMShape > &shapes, const bool replace=true)
Load a cad model represented by AMCAX TopoShape. Note: this import method does not specify any entity...
AMCAX::NextMesh::NMAPIModel::GenerateMesh
AMCAX_API void GenerateMesh(const std::string &configJson)
Generates the mesh for the current model based on provided configuration parameters.
AMCAX::NextMesh::NMAPIModel::EntityGetTag
AMCAX_API EntTag EntityGetTag(const NMEntity &ent)
get the tag of the given entity
AMCAX::NextMesh::NMAPIModel::GetMesh
AMCAX_API NMMesh GetMesh()
Get the mesh handle. Note one model only holds a unique mesh.
AMCAX::NextMesh::NMAPIModel::GetEntity
AMCAX_API NMEntity GetEntity(const DimType dim, const EntTag etag)
get the entity handle by entity tag and dimension
AMCAX::NextMesh::NMAPIModel::InitLogger
static AMCAX_API void InitLogger(const std::string &logFileName="", const std::string &logPattern="[%Y-%m-%dT%X%z] [%l] %v", const int64_t logFileSize=20 *1024 *1024, const int maxLogFiles=100)
set the logger. the logger is closed by default, if this function is not called
AMCAX::NextMesh::NMAPIModel::AddCompositeEntity
AMCAX_API NMEntity AddCompositeEntity(const std::vector< NMEntity > &entities, bool ignoreAdjSubEntity=true)
Generate a composite entity by ignoring the boundary entities between the connected input.
AMCAX::OCCTIO::OCCTTool::Read
static AMCAX_API bool Read(TopoShape &s, std::istream &is)
Read a shape from a stream.
AMCAX::NextMesh
Namespace of all interface in the AMCAX NextMesh module.
Definition misc.docu:42
AMCAX
Namespace of all interface in the AMCAX kernel.
Definition misc.docu:8
AMCAX::NextMesh::OutParams
Control parameters for exporting file.
Definition Macros.hpp:120

Click here example10 to get the full source code of the complete example. Everyone can download it as needed.