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Basic Information on views
Task: views
Purpose: Generate a projection of the datacube
Categories: visual display
VIEWS is a MIRIAD task which generates projections of a cube, viewed
as if the cube was rotating around its y axis. The view is also
from an angle "phi" to the x-z plane. The output is intended to be
fed into a tvmovie program, to view a rotating cube. The projection is
a thresholding operation -- pixels values less than the threshold are
transparent, a pixel greater than the threshold is opaque, with a
brightness given by the pixel value.
Key: in
This is the standard name for an input dataset -- usually
an image, though sometimes either an image or visibility dataset
or some foreign dataset format. Some tasks support multiple
input datasets at a time (with wildcard supported) whereas
others can handle only a single one at a time. There is
generally no default input name.
Key: region
the userguide.
This selects a subregion of an image. Multiple subregions can be
selected, which are "ored" together. The following subcommands are
recognized (each of which can be abbreviated to uniqueness).
images(z1,z2)
Select image planes z1 to z2 inclusive. z2 defaults to z1.
quarter(z1,z2)
Select the inner quarter of the image planes z1 to z2 inclusive.
If both z1 and z2 are missing, then all planes are selected. If
only z2 is omitted, z2 defaults to z1.
boxes(xmin,ymin,xmax,ymax)(z1,z2)
Select the pixels within a box with corners xmin,ymin,xmax,ymax.
z1 and z2 are the same as in the "image" subcommand. If z1 and z2
are omitted, all planes are selected.
polygon(x0,y0,x1,y1,x2,y2,...)(z1,z2)
Select the pixels within the polygon defined by the list of vertices.
z1 and z2 are the same as in the "image" subcommand. If z1 and z2 are
missing, all planes are selected. If only z2 is omitted, it defaults
to z1.
mask(file)
Select pixels according to the mask given in the file.
The units of the numbers given in the above commands are, in
general, absolute pixels. But this can be changed (and rechanged)
by using one of the following subcommands.
abspixel
Coordinates are interpreted as absolute pixel values, the default.
relpixel
Coordinates are relative to the reference pixel of the map.
relcenter
Coordinates are relative to the central pixel of the map,
(defined as (naxis1/2+1,naxis2/2+1)).
arcsec
Coordinates are in arcseconds, relative to the reference pixel.
kms
Coordinates in the third dimension are in km/s.
Key: out
The name of the output dataset, either image or visibility.
There is generally no default (although some tasks simply
do not produce an output if this is not set).
Key: phi
The elevation angle, with respect to the x-z plane, of the observer
(degrees). This must be in the range [0,90]. Default is 30.
Key: aspect
Aspect ratio of the different axes. Two values can be given, giving
the y/x aspect ratio, and the z/x aspect ratio. Default should be
fine.
Key: thresh
Threshold used in determining which details appear in the output.
Default is the average of the image minima and maxima.
Key: imsize
Size of the output cube. Default is 128x128x64 (should be adequate).