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Hello, Is it possible to calculate the position of something in Metapost, and to export that value to TeX such that I can use it in setups and things? I thought perhaps I could \def inside btex..etex. Here's a minimal example trying to illustrate the idea: \startuniqueMPgraphic{canon} path p, q; h := \overlayheight; w := \overlaywidth; % imagine this is more complex p = (0, 0) -- (w, .5h); q = (0, h) -- (w, 0); draw p; draw q; z0 = p intersectionpoint q; % btex \def\Z{ ypart z0 } etex; \stopuniqueMPgraphic \defineoverlay[canon][\uniqueMPgraphic{canon}] \setupbackgrounds[page][background=canon] \setuplayout[topspace=0pt, header=0pt, height=22cm] % here I would use \Z \showgrid \starttext xyz \stoptext Thanks, -- Kate