movie in axis low=? high=?
This routine takes a three-dimensional NDF and displays its two-dimensional slices sequentially on a grey or colour graphics device.
The colour table of the display is unaltered so that a previously loaded colour table will be used. Bad values will be displayed in the display background colour, which in general is distinct from the colour for the lowest (or highest) data value. This routine is quite primitive. It does not use axis data or spectroscopic values from the Specdre Extension. Pixels and slices in the cube are addressed by their NDF pixel indices, which are integer numbers, usually starting at 1. The routine also does not pay much attention to the precise timing of the display. The following list gives activities that the routine spends time on and how the user can exert some control over the timing. - Before a frame can be displayed it must be extracted from the cube. The time taken for this depends greatly on whether the frame counting axis is the first or last axis. Taking slices is fastest if AXIS=3 and can be very slow if AXIS=1, so it may be useful to re-arrange the axes of a cube that will be viewed often with the same frame-counting axis. Another way to reduce the time for taking slices from the cube is to use as small a cube as possible: If it is a-priori known that only a certain range of frames will be looked at, or that only a certain part of all frames is interesting, then the input cube can be given as an appropriate subset of the actual disk file. - Also before a frame can be displayed it must be converted according to the colour capabilities of the display. - Each frame needs to be extracted and converted only once and can be viewed several times, converted frames are kept in a workspace until the routine exits. - In the sequence displays each frame is converted and displayed before the routine goes on to the next frame. - When a specific frame is requested it is extracted, converted and displayed (unless it has been viewed before). - When the next or previous frame relative to the displayed one is requested, it is extracted and converted if necessary. Then it is displayed. In anticipation of another request of the same type the next or previous frame is extracted and converted immediately. - Even if a frame has been converted before, it takes some time to re-sample it from cube pixels to display pixels. This time can be minimised by choosing the fast mode, where a cube pixel is only one display pixel. - Disruptions occur in the display of a sequence of frames due to the unpredictable need for the machine to page memory. - Display may be over a network and bandwidth has to be shared with other users. This too causes disruptions of frame sequences. In summary, it may be best to - put on your spectacles and settle for the fast (and tiny) display, - decide which part of the cube is interesting and specify only that sub-cube as input, - begin the forward sequence to convert the whole input sub-cube, - have a cup of tea if AXIS=3 and the cube is not small, - use the options 'I', 'P', 'N' to look at individual frames in your own time. It is not possible to write the cube as converted for display. Such a cube would be of limited use, since it might contain only part of the input cube and since its scaling depends on the colour capabilities of the display used.
FIGARO A general data reduction system