[starlogo-users] patch and global variables...

[Ken Kahn]

Hi. Interesting points.

When there is a good use of patches, like the terrain example you give, then
I would rather see language support for modelling that with agents rather
than patches. I repeat -- what is a patch other than an immobile agent? From
a modelling perspective (rather than a programming one) why should trees be
modelled by patches while sheep by agents? I agree that terrain seems
different but I'm OK with using agents for that as well.

2D applications are based upon pixels which are small patches but 3D ones (
e.g. your "sophisticated VR environments") are typically based upon
triangles whose corners have x, y, and z coordinates. The graphics card
converts them to pixels for the display but those pixels are not part of the
programming model only the vectors making up the triangles.

Best,

-ken

On 12/03/07, josh <jbuhl_nospam at gmx.de> wrote:
>
> Dear Ken,
>
> I disagree with your statement whole-heartedly.  The idea that the
> agents can react to the different types of terrain they are standing on
> or in front of, etc., is very useful for the simulation/modeling nature
> of starlogotng. The /concept/ of patch variables is exactly how this
> should be done cleanly. What you suggest could be done internally to
> implement the patch variables efficiently and save computing resources,
> but as far as the programming interface and programming style go your
> suggestion is a not too pretty hack.
>
> While you are correct that sltng is currently confined to a rough grid,
> this is only a question of resolution. Digital fotography is also made
> up of little squares, but there are simply a lot of them, so a circle
> still looks like a circle.
>
> It would be interesting to be able to make the grid variable in size,
> then by adjusting the agent size, you could have whichever resolution
> you need to model the environment you want. I'm sure the most
> sophisticated VR environments we have today still can be  broken down at
> the lowest level into tiny pixels, i.e. a grid.
>
>
> -j
>
> Ken Kahn wrote:
> > Your patch variable example points to a shortcoming with the concept of
> > patches. If indeed only a few patches are poisoned then why not keep a
> > global variable listing the coordinates of the poisoned patches and
> > check for membership. The check may take a few extra nanoseconds but you
> > don't waste 10,000 memory locations.
> >
> > I'm glad to hear that "Patches are a less active part of StarLogo TNG"
> > since I dislike the idea of having something that are really agents but
> > they can't move. It just complicates the computation model. There can be
> > an efficiency argument for low-level support of non-mobile agents but I
> > think it is often less efficient to support patches -- e.g. the poison
> > example. Also it pushes one's model towards a uniform rectangular grid
> > while there are plenty of other ways to model the environment. Maybe
> > poison is spread out over circles of radius 10 while other variables are
> > at different patch sizes. Patches are too special purpose to be part of
> > a language.
> >
> > Best,
> >
> > -ken
> >
>
>
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