[plt-scheme] Re: Writing a game and have questions

From: Robby Findler (robby at cs.uchicago.edu)
Date: Sat Sep 20 15:51:31 EDT 2008

In the specific case of PLT Scheme's GUI toolkit, probably the easiest
thing to do is to both draw and determine if points are in regions via
region% object or dc-path% objects.


On Sat, Sep 20, 2008 at 2:35 PM, Neil Van Dyke <neil at neilvandyke.org> wrote:
> I don't know the answer to the offscreen buffer question.
> If you decide not to go that route, and these objects like monsters are not
> all bound to particular hex tiles or do not fill the tiles completely for
> purposes of picking (so you can't just find the hex tile and then check a
> data structure to see whether there's a monster associated with the hex
> tile), you might consider implementing this kind of object picking as a
> two-step algorithm.  The first step would be to determine which if any of
> the monster-like objects is clicked  (by, e.g., scanning linearly through
> lists of them and checking for point inside polygons, or by using a fancy
> computational geometry method).  The second step would be, if no
> monster-like thing was clicked, to use the simple arithmetic means of
> determining which hex tile was clicked.  I think that would be more of the
> CAD way of doing things, and it is not subject to some of the limitations
> and potential headaches of the off-screen pixel-peeping method.
> Probably for your game, either approach would be fine, but just thought I'd
> mention it, in case you have trouble with pixel-peeping or you later need to
> implement something that scale better.  (You did ask originally for other
> approach suggestions. :)
> Deep wrote at 09/20/2008 01:54 PM:
>> The reason for the offscreen buffer scheme was that its a bit more
>> general. In the sense that if tomm I was using some ill defined shapes
>> (like say a Monster which would be an image with alpha) I could still
>> render their outlines to the offscreen click map and get the results.
> --
> http://www.neilvandyke.org/
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