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ksnow & ktrek: displaying tabular data

ksnow and ktrek are simple programs to visualise points whose coordinates are in a table. For example, if you have a list of galaxies with X, Y and Z coordinates (like the table universe.tbl in /applic/viz/doc, courtesy Hélène di Nella, University of New South Wales), with ksnow you can see these points in a 3D representation and rotate this. With ktrek you can fly through these data points. Have a try with this table, the pictures are very nice. They show the local universe out to about 200 Mpc. (see example 3) Be aware that ksnow or ktrek require a lot of resources. They may not work on your workstation. They do work on phoenix.

ksnow and ktrek can be started with:

ksnow [-bg <bgcolour>]


ktrek [-bg <bgcolour>]

The optional switch -bg sets the background colour of the display window, otherwise it will have the default window background colour.

Table Format   

The first line in the table should give the range in X, Y and Z of the data points, in the format:

xmin ymin zmin xmax ymax zmax

The format for the data points is simple: there should be three columns, one for X, one for Y and one for Z. Optionally you can have a fourth column or a fourth value for some of the points. The values in this fourth column are used as brightness of the point. Every point for which there is no value in the fourth column will have brightness 1.0.

Lines in the table file that have # or ! as first character are taken to be commentlines and they are ignored. The extension of the table file should be .tbl.

Loading tables    

To load a table, click (left) on Load Table and click (left) on the name of the table you want to load. Loading the table takes some time because ksnow and ktrek scale the data.


ksnow and ktrek draw the points on the screen using a perspective projection. With the slider Depth you can determine how much perspective is used. The percentage corresponds to how much the depth range of the points is used. 100% is full perspective (i.e. the full depth is used), 0% is no perspective at all (i.e. orthogonal projection). Normally speaking a value of about 50 - 75% gives the best results. After changing the Depth the display is not updated automatically. Use the button Update for this.


The Scale slide sets the linear scale of the image, so can be used to soom in and out.


Update can be used to update the display. This can be used after changing the Depth or the Scale of the image.


The selection of a colourmap and the control of contrast etc. go in a slightly different way compared to the other programs: to modify the colourtable, drag (middle) in the display window. To select a colourtable, click (right) on "Colourmap" and choose one from the menu. To display the current colourtable in a separate window, click (left) on "Colourbar".

next up previous contents index
Next: ksnow Up: ATNF Visualisation Software Previous: kview: playing movies
Richard Gooch