Table of Contents

Name

snapsmooth - adaptive variable length smoothing

Synopsis

snapsmooth in=SnapShot(5) -file out=Image(5) -file [parameter=value]

Description

snapsmooth produces a binary file specifying a smoothed image of an N-body snapshot in the xy plane, with the smoothing length of each point determined by the distance to a nearby neighbor and by user-specified parameters. The headline string of the output file is an image of the parameter values and also shows the number of particles that were smoothed.

snaprotate(1NEMO) has to be used first to image any other than a top-view.

snaptrim(1NEMO) has to be used first to produce an image of any snapshot other than the first in a file.

Parameters

The following parameters are recognized in any order if the keyword is also given
in=SnapShot file
input file, in snapshot(5NEMO) format [no default, reads first snapshot]
out=Image file
output file, in binary image(5NEMO) format [no default].
sl=real slc=real
smoothing length will be (distance to kth nearby-neighbor) * sl + slc. Note that slc is measured in pixels, and is thus dependant on npix [default sl is 1, slc is 2.5% of npix]
k=int
the smoothing length will be a factor of the kth nearby-neighbor. The program uses a two-D tree structure to store the points, and repeatedly finds the point that encloses the smallest square around the target point, excluding those it has found already until it has found k squares [default is 1].
realnn=bool
false for nearby neighbor approximation, true for nearest neighbor (slower) [default false]. The nearby-neighbor approximation finds the point that encloses the kth smallest square around the target point, while the nearest neighbor algorothm takes the box found by the approximation, enlarges by the amount necessary to enclose a circle inscribing the square, sorts all of the points in the enlarged square by distance and returns the kth point.
every=int
read every everyth from snapshot for smoothing [default is 1]: this can help speed up processing of the image.
npix=int
the number of pixels to a side of the square onto which the program will smooth the image. The program will scale the image onto the array without distorting the image such that all the points will fit, with a margin for spread due to smoothing [default is 100].
sfunc=smoothing function name
the smoothing function is either "gauss" or "spline" (a smooth finite-bounded bell-shaped curve). The surface brightness of the image will be the total mass of the image.
gaussminval=real
minimum value of gaussian (maximum 1.0 at origin) [default 0.01]

See Also

snapshot(5NEMO) , snaprotate(1NEMO) , ccddisplay(1NEMO)

Author

Peter Wisnovsky

Files


~/src/pswisnov/snapsmooth    author’s original sources

Update History


xx-jun-87    Braught into system    PSW
12-jul-88    small mods for new filestruct and history    PJT


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