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README
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psa - Point Set Analysis
A tool for the analysis of two-dimensional point sets with applications in
graphics.
Overview
psa is a command line tool that takes two-dimensional point sets as input
and analyzes these point sets with respect to several spatial and spectral
statistics important for sampling problems in computer graphics. These
statistics include:
- Global minimum distance (smallest separation between any two points)
- Average minimum distance (average nearest-neighbor distance)
- Bond-orientational order (similarity to the hexagonal lattice)
- Effective Nyquist frequency (equivalent to Nyq. freq. in uniform sampling)
- Oscillations (metric for potential aliasing caused by the point set)
- Radial power spectrum
- Radial distribution function
- Anisotropy
- Fourier amplitude/power spectrum
For more information regarding these measures, consult our papers:
Daniel Heck, Thomas Schl\"omer, Oliver Deussen:
Blue Noise Sampling with Controlled Aliasing.
ACM Trans. Graph., 32(3):25:1-25:12, 2013.
Thomas Schl\"omer, Oliver Deussen:
Accurate Spectral Analysis of Two-Dimensional Point Sets.
Journal of Graphics, GPU, and Game Tools, 15:3, 152-160, 2011.
The latest version of psa can always be found at https://github.com/nodag/psa.
Any suggestions regarding the concepts or the implementation of psa are very
welcome. Feel free to contact us via http://thomas-schloemer.org.
Dependencies
- cairo (http://www.cairographics.org) for PDF and PNG output
- CGAL (http://www.cgal.org) for the bond-orientational order
The CGAL dependency is not strict and can be removed by setting HAVE_CGAL to 0
in the accompanying Makefile. The computation of the bond-orientational order
is then omitted. psa also makes use of OpenMP if available.
Usage
Type
./psa filename [options]
to analyze the given file(s). When called without any parameters, psa
generates a single PDF containing all measures. Use --avg if you want to
average all measures over the given files, e.g.
./psa --avg points/mypoints*.txt
Type
./psa --help
for a list of available options.
File Formats
Point set files are supported in three flavors:
- TXT: plain text files with a pair of coordinates for each point
- RPS: raw single-precision floating point data
- EPS: coordinate pairs for each point with a basic EPS header that is
understood by most EPS viewers
An example for each format is included in /points. Use --convert to convert
files between the three formats. Note that psa cannot read arbitrary EPS
files.
License and Acknowledgements
psa is free software and published under the GNU GPL. For further information
see the file COPYING. This software has been partially funded by DFG, German
Research Foundation, and the PhD Program 'Explorative Analysis and
Visualization of Large Information Spaces'.
Copyright (C) 2011-2015
Thomas Schl\"omer
Daniel Heck
Version History
v1.1a
- Fixed some Linux/gcc compile issues
v1.1
- Made oscillations metric independent of effective Nyquist frequency; the metric is now in line with the upcoming ACM TOG paper
v1.0
- psa has been totally rewritten
- Added new statistics: effective Nyquist frequency, oscillations metric, and
orientational order (the latter needs CGAL)
- Added new 1D measure next to radial power spectrum and anisotropy: radial
distribution function
- Added option --raw to write the raw data of all 1D measures for better
post-processing using external tools
- 1D measures are now written as TEX source files based on the TIKZ package
for cleaner integration into larger documents and potential final touches
- Added options to generate every measure separately
- Added configuration file 'common/psa.cfg' for most important variables
- Can now directly read points from certain EPS files next to TXT and RPS
- Added option --convert to convert points between these formats
- Dropped need for fftw-library
- Dropped computation of star discrepancy
v0.2.2
- Added average mindist measure
- Removed non-toroidal distance measure
- Normalized radius is now called normalized mindist
- Changed default plot colors to black
- Improved code readability
v0.2.1
- Bug fixes with respect to cairo version >1.10.0
- Fixed some MS VS compilation issues
v0.2
- Integrated an optional DFT using the fftw-library
- Non-spectral measurements are now also rendered into summary files
- Added non-toroidal minimum distance computation
- Support for more arbitrarily many point sets in a single directory
- Bug fixes
v0.1
- Initial release