Hi Hans and Taco, The latest beta solves the problems metioned by Thomas Schmitz and myself concerning \uniqueMPgraphic: many thanks for your attention. However, I observed the following regarding \processMPbuffer: some grahpics don't show up when tyepset with mkiv, while they are fine with mkii. (This with mkiv, LuaTeX revision 2, (LuaTeX date stamp 2008102016), ConTeXt version 2008.10.23 17:32). (For the Chief of Rumour Control: it is not crucial to address the reported bug urgently…). Best regards: OK %% begin bug-processMPbuffer.tex \setupcolors[state=start] \starttext \startbuffer[axes-1] textextoffset := ExHeight ; numeric u ; u := .5cm ; vardef arrowheadonpath (expr p, s) = save autoarrows ; boolean autoarrows ; autoarrows := true ; set_ahlength(scaled ahfactor) ; % arrowhead p if s<1 : cutafter (point (s*arclength(p)+.5ahlength) on p) fi enddef ; path xox ; xox := (-u,0)--(8u,0) ; path yoy ; yoy := (0,-u)--(0,7u) ; draw xox withcolor blue ; draw yoy withcolor blue ; ahfactor := 4 ; % default is 2.5 fill arrowheadonpath(xox,1) withcolor .625blue ; % try .25 fill arrowheadonpath(yoy,1) withcolor .625blue ; % try .25 \stopbuffer \startbuffer[chemin-1] textextoffset := ExHeight ; numeric u ; u := .5cm ; z1 = (5u,0) ; z2 = z1 rotated 60 ; z11 = z1 rotated 15 ; z12 = z1 rotated 30 ; z13 = z1 rotated 45 ; z0 = (2u,0) rotated 30 ; path gamma ; gamma := (0,0)--(5u,0) ; draw gamma withpen pencircle scaled .4mm withcolor .625yellow ; path gammaR ; gammaR := z1..z11..z12..z13..z2 ; draw gammaR withpen pencircle scaled .4mm withcolor .625yellow ; dotlabel.bot (btex \switchtobodyfont[10pt] \strut $R$ etex, z1) ; path gammaRR ; gammaRR := z2--(0,0) ; draw gammaRR withpen pencircle scaled .4mm withcolor .625yellow ; dotlabel.top (btex \switchtobodyfont[10pt] \strut $R{\rm e}^{2{\rm i} \pi/n}$ etex , z2) ; dotlabel.rt (btex \switchtobodyfont[10pt] \strut ${\rm e}^{{\rm i}\pi/ n}$ etex , z0) ; label.rt (btex \switchtobodyfont[10pt] \strut $\Gamma_{R}$ etex , z11) ; fill arrowheadonpath(gamma,.4) withcolor .625yellow ; fill arrowheadonpath(gammaR,.4) withcolor .625yellow ; fill arrowheadonpath(gammaRR,.4) withcolor .625yellow ; \stopbuffer This file has been typeset on \currentdate{} at \currenttime, with \doifmodeelse{mkiv} {mkiv, LuaTeX revision \luatexrevision, (LuaTeX date stamp \luatexdatestamp)} {mkii, using the command: \type{texexec basic-test.tex}}, ConTeXt version \contextversion. % LuaTeX version \luatexversion, This MetaPost graphic is shown with mkiv: \placefigure[middle][-]{none}{\processMPbuffer[chemin-1]} {} \blank but not this one \placefigure[middle][-]{none}{\processMPbuffer[axes-1]} {} \blank nor this one \placefigure[middle][-]{none}{\processMPbuffer[axes-1,chemin-1]} {} \stoptext %% end of bug-processMPbuffer.tex