...

input metaobj; beginfig(1) fill fullcircle scaled 1cm withcolor red; color t; t:=(1,1,0); %setObjectDefaultOption("Box")("fillcolor")(t); newBox.test(""); Obj(test).c=origin; drawObj(test); endfig;

end.

Your color is not transparent, so it will work as expected: no white box.

??? The example demonstrated that it *IS* drawn white box in the background of every metaobj object. Exactly as you mentioned. But I had a second look into mpobj.mp and probably find out the white box tiger. Comment line 750: unfill BpathObj(n); I am sure this hack will cause some unpleasant side-effects (e.g. with shaded boxes) but in some limited situations... Vit Zyka