On 2-5-2012 17:35, Alan BRASLAU wrote:
I have a MetaPost question concerning drawarrow withtransparency (or any other compound object).
Is there some clever way to achieve uniform transparency for a compound object? For example, in the minimal example below, how can one obtain a transparent arrow without getting an X-ray vision of the arrowhead?
\starttext \startMPpage drawarrow origin--(1cm,0) withtransparency(1,.5) ; drawarrow origin--(0,1cm) withtransparency(1,.5) ; \stopMPpage \stoptext
This is a side effect of an arrow being a composed graphic. I experimented a bit with transparency grouping and after several variants I settled to the following approach: \starttext \startMPpage[offset=1mm] drawarrow (1cm,0cm) -- (0cm,0cm) withcolor red withtransparency(1,.5) ; draw image ( drawarrow (1cm,0cm) -- (0cm,0cm) withcolor red withtransparency(1,.5) ; ) shifted (0,2mm) asgroup "" ; draw image ( drawarrow (1cm,0cm) -- (0cm,0cm) withcolor red withtransparency(1,.5) ; ) shifted (0,4mm) asgroup "isolated" ; draw image ( drawarrow (1cm,0cm) -- (0cm,0cm) withcolor red withtransparency(1,.5) ; ) shifted (0,6mm) asgroup "knockout" ; draw image ( drawarrow (1cm,0cm) -- (0cm,0cm) withcolor red withtransparency(1,.5) ; ) shifted (0,8mm) asgroup "isolated,knockout" ; addbackground withcolor green ; \stopMPpage \stoptext As we have to use xforms (a pitty that this is needed) there is the usual interference and something fishy with clipping is going on. Hans ----------------------------------------------------------------- Hans Hagen | PRAGMA ADE Ridderstraat 27 | 8061 GH Hasselt | The Netherlands tel: 038 477 53 69 | voip: 087 875 68 74 | www.pragma-ade.com | www.pragma-pod.nl -----------------------------------------------------------------