Re: [pygame] Working with maps

[Thiago Chaves <shundread@xxxxxxxxx>]

Computational geometry alternative:

You can do it with geometric shapes. Make the states/countries
polygons. Triangularize the polygons and then it is a matter of
finding out whether the (x,y) coordinate is inside one of the
polygon's triangles.

See here: http://en.wikipedia.org/wiki/Polygon_triangulation

-Thiago

On Tue, May 18, 2010 at 11:02 AM, Timothy Baldock <tb@xxxxxxxxxxxxx> wrote:
> Hi Kenny,
>
> I'd do this by making each country a sprite with a transparent
> background (colour-key transparency would work), then whenever the user
> clicks doing a collision detection between the position of the mouse
> cursor (first use rect-collision to build a small number of tiles which
> match, then do pixel-perfect collision based on alpha - i.e. using the
> sprite's mask). Easiest way to do this IMO is to draw an "invisible"
> (e.g. position the sprite, but don't actually draw it to the screen)
> 1x1px sprite at the position of the mouse cursor, then collide that
> against the group containing all the country sprites.
>
> This technique means the countries can be any colour you want, or the
> colour can change without messing things up. I used this method for my
> isometric game engine to allow selection of tiles and other objects and
> found it to be quite fast.
>
> Thanks,
>
> Timothy
>
>
> On 18/05/2010 05:09, Kenny Meyer wrote:
>> Hey,
>>
>> I'd like to work with irregular formed geometric shapes like those in of
>> country maps in pygame.
>>
>> I want to do the following:
>> "Divide" a country map into its states and provinces and make each of them
>> "click-able", where the map could be an image (*.png) or maybe a vector graphic
>> (*.svg).
>>
>> The result should be:
>> A game where to guess and click the name of the state and province on a map.
>>
>> Observations:
>> It would be quite difficult to assign each state/province fixed coordinates as
>> those are irregular geometric shapes.
>>
>> Any ideas, pointers to other projects or suggestions?
>>
>