Re: [pygame] Isometric Math

[Jasper <jasper@xxxxxxxx>]

> -How do I do "picking," identifying the tile or character a user has
> clicked on? I can imagine calculating it for a flat iso landscape, but
> taking height into account all I've come up with so far is to save a
> bunch of bounding rectangles and test them inefficiently.


Sorry for replying indirectly.  I'd deleted the original email, and the 
archives seem to be down.

Anyway, if you're rendering things in 3D w/ opengl, there is a straight 
forward trick that'll handle this, and I imagine something similar could 
be done for a strictly 2D isometric game.

For example I have a hex map, which is rotated into the screen to a 3/4 
perspective, along with various "billboards" for game-pieces that stand 
on the map.  You can find screenshots showing what I'm taking about here:
http://brass-golem.com/?page_id=7

Each hex and piece has an associated "mouseMap", which is the same shape 
with all opaque pixels converted to pure white.  When reading what the 
mouse is pointing to, I draw one frame of the scene off screen using the 
mouseMaps, with each having a colorFilter that encodes a number (this 
way the hexes can all share the same texture, and varry only their 
colorFilter).  So each hex mouseMap is drawn with an RGB color of 
(x,y,0), while game-piece mouseMaps are drawn with RGB = (0,0,id).  Then 
I read the color of the screen pixel the mouse points to, and decode it 
to precisely determine what hex/piece is picked.

Hope this helps,
-Jasper