geometry3cpp

Open-Source (Boost-license) C++11 library for geometric computing.

geometry3cpp is an in-progress port of geometry3Sharp, the gradientspace C# library for geometric computing. (Except the parts of that library that were ported from the C++ WildMagic/GTEngine libraries, we just use those directly)

WORK IN PROGRESS - HARDLY TESTED - BUYER BEWARE

Goals

g3cpp is intended to be a general-purpose high-level geometric computing package, with a focus on triangle mesh processing. It includes other math libraries which provide most of the low-level vector math stuff, solvers, etc.

I would like the library to be a header-only library. However the WildMagic5 dependency is currently structured to produce a compiled library, and GTEngine is also not fully header-only, there are few .cpp files. My intention is to eventually refactor these libraries so that they are fully header-only as well.

Note: I would welcome comments about whether a header-only approach is suitable/desirable for production use.

Current State

The dependencies contain an enormous amount of functionality, much more than geometry3Sharp, at the lower level. At the mesh level the following classes have been ported

• DMesh3 - dynamic mesh, fully ported
• DMeshAABBTree3 - AABB bounding volume hierarchy for DMesh3, only nearest-point and generic traversal currently ported
• Remesher - majority ported, no parallel smoothing/projection currently
• OBJReader and OBJWriter - functional but support for materials/texture maps is not fully ported

Old Code This repository has evolved from an earlier attempt (pre-geometry3Sharp) at a mesh processing library. This previous code has not been fully deleted/updated, but will be.

goemetry3_tests project has some basic sample code in main.cpp. The CMake generators add this as a separate project, and it generates a standalone executable linking to g3Cpp. If you want to just try something out, I would recommend starting here.

Dependencies

All dependencies are included in the repository, for convenience.

1. Eigen , the C++ template library for linear algebra: matrices, vectors, numerical solvers, and related algorithms (according to their website). MPL2 License. Header-only, source included in /external/Eigen for ease of compiling, but you could probably get CMake to look somewhere else. The Vector types (Vector2d, Vector3d, etc) in g3cpp are Eigen vectors.

2. WildMagic5 from GeometricTools, written by David Eberly. Boost License. Only the LibCore and LibMathematics components. Vector math, Geometric intersection and distance tests in 2D and 3D, containment fitters, geometric approximations fitters, Computational Geometry algorithms, Numerical methods, rational number types, 1/2/3D interpolation methods. It's amazing, I've been using WildMagic for 10+ years, since version 2. The source is included in the /external/ subdirectory. This library is no longer maintained and so I have made various local changes to ease porting from the C# version and make it easier to pass vector types between Eigen and Wm5.

3. GTEngine also from GeometricTools and written by David Eberly. Boost License. Only the Math parts, again. This is the "next version" of WildMagic5, however quite a few of the classes from Wm5 were not ported. However it has some new things like Constrained Delaunay. So both are included. The source is included in /external/GTEngine. Namespace for this one is "gte". *(Currently not actually called by the g3cpp code, but it will be)

4. libigl, the C++ header-only mesh/geometry processing library. libigl is built on Eigen and has implementations of most standard geometry processing algorithms/techniques. Source is included in /external/libigl. MPL2 License is used for the core library, and this is all that geometry3cpp will call. However the code includes calls to various other libaries, including CGAL, LGPL/GPL-licensed code, etc. These will not be included in your binaries unless you explicitly call them via the igl::copyleft:: namespace.

Building

Currently only definitely working on Windows, but the code should be portable..."should"...*

1. Run bin\get_cmake.bat to download and unzip the required version of CMake. This will be unzipped in bin\cmake_win, it will not affect your system installation of CMake (if installed).

2. Run external\cmake_install_eigen.bat. This does some cmake stuff so that the Eigen CMake module can be found. Again, it doesn't affect any other Eigen installations/etc. (Not entirely clear why this is necessary, but CMake cannot find Eigen without it)

3. Run top-level StartVS2017_Debug.bat or StartVS2017_Release.bat to run CMake and automatically open the resulting VS2017 solution.

If you are actively working on the g3cpp code, UpdateVS_Debug_2017.bat will regenerate the solution file, which will cause VS2017 to prompt you to reload it.

Packaging / Build Output

Currently a dll, output to visual studio build folders, ie build\Win64_Debug or _Release.

You can switch to a static .lib by editing src\CMakeLists.txt and commenting/uncommenting the relevant block (see comments in file)

No packaging as of yet. You will have to add the various header source folders to other projects. Sorry!! (happy to take PRs here!)

Testing

There isn't any, yet.

libigl interop

Since libigl also uses Eigen, many things are compatible. The main interop required is in passing meshes between the libraries. libigl uses Nx3 Eigen matrices for vertices and triangles (Eigen::MatrixXd and MatrixXi, respectively). More details in their tutorial. g3cpp provides functions to convert to/from DMesh3 as follows:

Eigen::MatrixXd V; Eigen::MatrixXi F;   // your libigl mesh
DMesh3 mesh(V,F);                       // convert to DMesh3
mesh.ToIGLMesh(V,F);                    // convert DMesh3 to libigl mesh. Resizes V and F.

Note that ToIGLMesh() properly handles gaps in the index spaces (ie if vertices or triangles were deleted), so there will not be a 1-1 correspondence between DMesh3 vert/tri indices and libigl row indices unless the DMesh3 is compact.