This fork is a triangle-only surface mesh-only version of Netgen which is optimized for use in real-time 3D graphics applications. With a small CSG mesh, defining the CSG, meshing, and drawing can perform at > 60 fps.
I originally wanted to use the functionality provided from Nglib as part of Netgen to do realtime CSG operations and produce a triangle surface mesh for rendering with OpenGL. However, this library does not:
- Include access to the CSG functionality.
- Provide for surface mesh generation from a CSG operation.
- Break apart the extra features, such as tetrahedral volumetric mesh generation, into separate modules.
Because my intended application of Netgen -- realtime 3D graphics/games -- is not the same as most users of Netgen -- Finite Element Analysis or Computational Fluid Dynamics -- I forked the library to remove features I would not be using, attempted to improve performance, and gained access to the functionality buried inside Netgen.
The projects I wrote to take advantage of this fork have been put on indefinite hold, so this project has also been put on indefinite hold.
- Only triangle surface meshing functionality (from a series of C++ commands or from a .geo file) is available.
- The directory structure is been flattened.
- Some early optimization attempts have been made.
- Access to the geometry specification / mesh generation APIs have been rewritten for ease of access.
File loading and mesh generation with default meshing parameters
From a .geo file
#include "ng\csg.hpp"
/* Your other code */
netgen::Mesh *pMesh = NULL; // Resulting triangle surface mesh
std::string filename ("scripts/ngdemo.geo");
netgen::CSGeometryRegister regr;
netgen::CSGeometry *pGeom = regr.Load(filename);
netgen::MeshingParameters mParams;
pGeom->GenerateMesh(pMesh, mParams);
delete pGeom; // Done with the geometryIn the C++ code
#include "ng\csg.hpp"
/* Your other code */
netgen::CSGeometry *pGeom = new netgen::CSGeometry;
// Define a cube
netgen::Point<3> pa = netgen::Point<3>(0, 0, 0);
netgen::Point<3> pb = netgen::Point<3>(1, 1, 1);
netgen::Primitive *ncube = new netgen::OrthoBrick(pa, pb);
pGeom->AddSurfaces(ncube);
netgen::Solid *cube = new netgen::Solid(ncube);
// Define a cylinder
netgen::Point<3> pac = netgen::Point<3>(0.5, sidePos, -1.1);
netgen::Point<3> pbc = netgen::Point<3>(0.5, sidePos, 1.1);
netgen::OneSurfacePrimitive *surf = new netgen::Cylinder(pac, pbc, 0.3);
pGeom->AddSurfaces(surf);
netgen::Solid *cyl = new netgen::Solid(surf);
// Yet another cylinder
netgen::Point<3> pad = netgen::Point<3>(0.5, -1.1, sidePos);
netgen::Point<3> pbd = netgen::Point<3>(0.5, 1.1, sidePos);
netgen::OneSurfacePrimitive *surfr = new netgen::Cylinder(pad, pbd, 0.2);
pGeom->AddSurfaces(surfr);
netgen::Solid *cylr = new netgen::Solid(surfr);
// Subtact the cylinders from the cube
netgen::Solid *cylinder = new netgen::Solid(netgen::Solid::SUB, cyl);
netgen::Solid *solid = new netgen::Solid(netgen::Solid::SECTION, new netgen::Solid(netgen::Solid::SECTION, cube, cylinder), new netgen::Solid(netgen::Solid::SUB, cylr));
// Setup the top level object for meshing
netgen::Flags flags;
pGeom->SetSolid("Root", new netgen::Solid(netgen::Solid::ROOT, solid));
pGeom->SetTopLevelObject(solid);
pGeom->SetFlags("Root", flags);
pGeom->FindIdenticSurfaces(1e-8*pGeom->MaxSize()); // Initializes surfaces
// Generate the mesh
netgen::Mesh *pMesh = NULL;
netgen::MeshingParameters mParams;
pGeom->GenerateMesh(pMesh, mParams);
delete pGeom; // Done with the geometry.Extracting indexed triangle mesh from the resulting mesh
/* Included in the header */
struct vertex
{
float x, y, z;
};
/* After the mesh generation code provided above */
// Vertices
int pointCount = pMesh->GetNP()*3;
vertex *pVertices = new vertex [pointCount];
for (int i = 1; i <= pMesh->GetNP(); i++)
{
const netgen::Point3d& p = pMesh->Point(i);
pVertices[i - 1].x = (float)p.X();
pVertices[i - 1].y = (float)p.Y();
pVertices[i - 1].z = (float)p.Z();
}
// Indicies
int indexCount = pMesh->GetNSE()*3;
GLuint *pIndicies = new GLuint[indexCount];
for (int i = 1; i <= pMesh->GetNSE(); i++)
{
const netgen::Element2d& el = pMesh->SurfaceElement(i);
for (int j = 1; j <= el.GetNP(); j++)
{
pIndicies[(i - 1)*3 + (j - 1)] = (el.PNum(j) - 1);
}
}For a full example, see this library as used in the Volumetric-CSG-Texture-Mapping application, available on GitHub.
- There's a lot of optimization work that could be done.
- Making this library compilable into a DLL would be nice (even though this is LGPL licensed, just like Netgen).
- Making it easier to create basic shapes.
- Adding more basic shapes.