deformability maps

[psychotomus]

like in worms... how do you do something like that?

[jeroen79]

In worms the map is a bitmap.
Part of the bitmap is made transparant, thus forming the the part that is not 'ground'.
Bombs then make the part of the map where they explode transparant in a circular pattern.
This can be done with simple bitmap drawingfunctions and blitting.

[Paul M]

The top part of the bitmap should be the alpha layer, to do this just use the magic wand tool and delete key to do this in photoshop

http://www.ziggyware.com/readarticle.php?article_id=154

That article is XNA specific but the same concept applies to any language.