thanks for the help guys.
i think that the reason i couldn't get it to work using just the one texture was the lack of colour variance between the blocks and the mortar.
i can see how this would work with the bricks you've shown, dwight, and any other contrasting colours. but i think the only way for me is the double texture route - using a transparent one for the bump.
now . . . where are those tutorials . . .
~/archiben
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