CGIL

Computational Geometry Interpolation Library

Prerequisite

• C++ Compiler supporting C++17 or newer
• CMake >= 3.19.0
• Boost C++ headers only portion
• CGAL headers only portion
  • Automaticaly downloaded during Build phase

Configuration

1. Create a build directory (for instance inside the source tree):

cd CGIL
mkdir build
cd build

2. Configure your system to have the proper libraries visable to the CMake build system:
   Note: These rules and variables used by CMake and not part of the CGIL application

• Boost
  • CMake will check BOOST_ROOT then system paths for Boost libraries

> export BOOST_ROOT=/my/dir/to/boost/1.71.0     # Boost Installation

3. Run cmake to generate the Makefile:

cmake ..

Build

Building the application has one extra complexity the way it's currently configured. If the CGAL library is not already found it will download and configure CGAL within your build directory. Therefore, you will need internet access and ports that allow access to the GitHub repository of CGAL.

To build the command is the same.

> make

Installation

Standard process to install into the bin directory

> make install

How to Use

At this stage several programs have been installed into the bin directory

> cd bin
> ls
cgil2  cgil3  make_random_sources  make_random_targets

We can use these to see the program behavior and expected file formats

Create random source values

To create random source values we can use the "make_random_sources" application. The program accepts 3 command line arguments or will defualt them if not provided.

make_random_sources <num_dim> <num_points> <num_variables>

Here we will create 1000 3D points with 2 made up variables and save to a file name "source.txt"

> ./make_random_sources 3 1000 2 > source.txt

Create random target locations

To create random target locations we can use the "make_random_targets" application. The program accepts 2 command line arguments or will defualt them if not provided.

make_random_targets <num_dim> <num_points>

Here we will create 1000 3D points and save to a file name "target.txt"

> ./make_random_targets 3 1000 > target.txt

Run Interpolations

To interpolate source values to target locations we use the "cgil2" or "cgil3" programs depending on 2D or 3D data. Again we can provide 2 command line arguments which in this case are the source and target file names. If none are provided it will expect the default names which we just used in the previous steps.

cgil2 <source_file> <target_file>
cgil3 <source_file> <target_file>

In this case we used the default names "source.txt" and "target.txt" so we can run without arguments and save the answers to a file named "interps.txt"

> ./cgil3 > interps.txt

Potential Issues

1. Interpolated values are 0's

If a target location is not found inside the convex hull of the source locations this will occur.
In fact, special steps were taken inside the "make_random_" applications to ensure all targets would be inside the convex hull of the sources.

2. Others?