CSG-EB

This library is for parsing Constructive Solid Geometry (CSG) for use in AMReX Embedded Boundaries (EB).

CSG is a file format used by the open source CAD modelling tool OpenSCAD. CSG is a subset of the SCAD language, equivalent in the kinds of geometries that can be expressed, but with fewer primitives (OpenSCAD can export .scad files to .csg). SCAD code is easier to read and write by humans; CSG files are easier to parse and process by software.

Dependencies:

• PEGTL for parsing
• Catch2 for testing framework
• CGAL for geometry computation

How to Build

Build dependencies

• C++17 compiler (GCC >=7.x, Clang >=5.x)
• CMake >=3.14
• Conan (CMake will try to install Conan if conan is not in PATH)

CMake will try to install Conan if conan is not in PATH. However, installing Conan (pip install conan) is recommended for faster builds.

Build

> cmake -S . -B build -DCMAKE_BUILD_TYPE=Release
> cmake --build build

Run tests

> cd build
> ctest

Using CSG-EB in your project

• Include the header file csg.hpp
• Call csg::get_csgif with the path to a CSG file to create an Implicit Function object.

#include <csg.hpp>

// for EB2::makeShop
#include <AMReX_EB2_GeometryShop.H>

...


auto csg_file = "~/my_geometry.csg";
auto is_internal_flow = true;

auto csg_if = csg::get_csgif(csg_file, is_internal_flow);

auto gshop = EB2::makeShop(*csg_if);

Note on the return value

If is_internal_flow==true, the CSG geometry defines a hollow space for the domain:

• csg_if(x, y, z) < 0 ⇒ (x, y, z) is INSIDE
• csg_if(x, y, z) > 0 ⇒ (x, y, z) is OUTSIDE

If is_internal_flow==false, the CSG geometry defines a solid boundary to the domain:

• csg_if(x, y, z) < 0 ⇒ (x, y, z) is OUTSIDE
• csg_if(x, y, z) > 0 ⇒ (x, y, z) is INSIDE

Add to the CMake build

• Add this repo as a CMake subdirectory in your CMakeLists.txt:

add_subdirectory(/path/to/repo/csg-eb)

• Add the csg target to the CMake target that uses code like in the the above example:

target_link_libraries(<target> PRIVATE csg)