StraightSkel is an implementation of the Straight Skeleton in 2- and 3-dimensional space. It is used to animate the computation of offsets of polygons and polyhedrons. StraightSkel was written by Gernot Walzl in the years 2011, 2012, 2013.
- C++ Compiler (≥C++17) http://gcc.gnu.org/
- CMake build system http://www.cmake.org/
- SQLite http://www.sqlite.org/
- OpenGL Utility Toolkit (GLUT) (often part of the graphics card driver) http://freeglut.sourceforge.net/
Optional:
- Computational Geometry Algorithms Library (CGAL) http://www.cgal.org/
- Doxygen http://www.stack.nl/~dimitri/doxygen/
"build.sh" does an "out-of-source build". It creates the binaries in a directory called "build". A database of some given polygons is created also.
CMake is used as build system. Therefore you may use "ccmake" or "cmake-gui" to configure the build process.
This is useful to switch to the exact geometric kernel of CGAL. The included kernel uses double precision only.
Key bindings and various options may be found in the configuration file called "StraightSkel.ini". This file is located in the same directory as the executable itself.
The usage of StraightSkel is printed to standard output when the command is invoked with no options.
Common problems:
- Plane equations are not exact: Many commonly used file formats (like Wavefront's .obj) have a number representation with limitations. It is not always possible that more than 3 points are exactly on the same plane.
- Degenerated input: More than 1 event occurs exactly on the same offset.
Creating animations: The OpenGL window can be dumped to a bitmap file (.bmp) by pressing the associated button. (default: F10) A series of bitmap files may be converted to an animated GIF using ImageMagick's convert:
convert -delay 100 -loop 0 -colors 64 *.bmp animated.gif
To create a movie you may use mencoder:
mencoder 'mf://*.bmp' -mf type=bmp:fps=10 -ovc xvid -xvidencopts bitrate=1000 -o output.avi
The build process can be configured to use doxygen to create documentation from the source code. Once the makefile is configured, "make doc" will invoke doxygen.
Additional documentation may be found inside the "doc" folder.
To avoid segmentation fault errors, standard C pointers are used very rarely. A slightly modified version of Boost's Smart Pointer is used instead. (Modification: Print the stack trace in case of an error.)
Organization of Source Code:
src/ algo/ Algorithms data/ Data Structures db/ Database kernel/ Geometric Kernel (double precision) ui/ User Interface gl/ OpenGL ps/ PostScript util/ test/ Unit Test Cases
Testing: Testing is a very important part to improve the quality of the code. "test.sh" tests the executable by invoking the command on many polyhedrons. A summary is shown at the end.
Unit Test Cases: Unit tests also document the usage of the code. The build process needs to be configured to build the tests. "make test" will sequentially run all "*TestRunner". "*TestRunner --log_level=all" gives detailed output.
Debugging: gdb is useful to detect errors.
gdb ./StraightSkel run 3d load anything.obj
Profiling:
valgrind --tool=callgrind ./StraightSkel 3d load anything.obj --no-window kcachegrind callgrind.out.*
sqlite3 skeldata2d.db3 "SELECT * FROM Polygons" sqlite3 skeldata3d.db3 "SELECT * FROM Polyhedrons"
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