General HydroStatics
Ship Stability Software
Command of the Week
(New or interesting aspects of GHS that you may not know about)


CHANGE is a boastful command. Like a politician, it promises more than it delivers. But that's where the similarity ends because you can make good use of GHS for many years and not be aware of CHANGE, and your life will not be the worse for it.

As of this writing, CHANGE is able to change only two things: 1) the words we call descriptions that are attached to tanks (also fixed-weight descriptions); and 2) the shades of color assigned to tanks.

Tanks have color attributes which determine the color of the contents when displayed in Condition Graphics (that is via the DISPLAY STATUS command). Without the meddling of CHANGE, the colors sensibly represent the specific gravity of each tank's contents. But if you have another purpose in mind for color, you can make up your own scheme.

To view all the available colors, try this dynamic display:

read SV.GF /quiet
tank *
load 1
display status /sync
macro x
   change * /color:%1
   if %1=0 then wait 3 else wait 0.5
   variable c=%1
   set c={c} plus 1
   if {c}>14 then set c=0
   exit x {c}
.x 1

If you looked over the code above, you noticed that the wait for color zero is longer. Normally zero would be black, but when the background is black, that would make the tank's contents disappear in the graphic. So instead of black, it restores the original color-assignment mechanism, which goes by density. Colors representing density are interesting and informative, deserving of the longer pause.

In Load Editor, your custom tank colors will color the Tank Description column as well. This has been used to mark cargo tanks in like colors according to their association in a piping system. If the color zero is in effect, the description is gray. Why not colored according to density, like in the graphic? Good question. If anyone has an answer, let us know.

One other thing CHANGE /COLOR does for tanks: In the graphics where the outline of the vessel is shown, tank reference points appear as little blobs whenever they have been relocated away from the origin. The color of these points (which normally matches tank outlines), follows the color determined via the CHANGE command. An example of this is shown below.

Did someone go through and string these lights by hand? That would be no fun. The commands that made it happen are those you see on the screen. This will work for any vessel since the tank list is generated automatically. (That should be the topic of a future COW.)

Someone wanted CHANGE /COLOR, believe it or not. Most of GHS is really the product of ideas and requests and demands from its users. Not too many demands, though. GHS users are generally a happy bunch.
Questions, comments, or requests?
Contact Creative Systems, Inc.

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Mailing address:
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Port Townsend, WA 98368 USA

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