Getting all records in a relationship - how can I do this in a cleaner way?

http://pastie.caboo.se/79914 - i'd like to get all of the graphics of
a certain *category* (not theme) by specifying the category id, but
none of the graphics are associated with a category_id, just a
theme_id. I included a solution I wrote that works fine, but it looks
incredibly ugly and there has to be a "cleaner" way. Any ideas?

http://pastie.caboo.se/79914 - i'd like to get all of the graphics of
a certain *category* (not theme) by specifying the category id, but
none of the graphics are associated with a category_id, just a
theme_id. I included a solution I wrote that works fine, but it looks
incredibly ugly and there has to be a "cleaner" way. Any ideas?

Graphic.find(:all, :include => [:themes => :categories],
:conditions => ["categories.id = ?", params[:id]])

Or something close to that.