Hi, I'm using Therion to map waterfilled caves, and some systems have 'air-locks' (air chambers), so it's necessary to distinguish between air filled cave, waterfilled cave and water surfaces. But the waterfilled area should show details (be transparent) in same way as dry cave. Is there any way to adjust the opacity value (in meta code?) when setting a transparent color? I have made a test to show my issues: The files can be found on http://www.staven.no/cavetest/ The cave (ca 100m long) plan: -> http://www.staven.no/cavetest/testcave_plan.pdf elevation: -> http://www.staven.no/cavetest/testcave_elevation.pdf This doesn't work to well draw underwater maps. *** Changing the water color: layout test code metapost def a_water (expr p) = T:=identity; thfill p withcolor (0.8, 0.8, 1.0); enddef; endcode endlayout -> http://www.staven.no/cavetest/testcave_elevation_2.pdf Looks better but the cave and line 'behind' doesn't show thru the water. *** Try with transparent water color: def_transparent_rgb(tr_lblue, 0.80, 0.80, 1.00); def a_water (expr p) = T:=identity; thfill p withtransparentcolor tr_lblue; enddef; -> http://www.staven.no/cavetest/testcave_elevation_3.pdf *** Almost perfect, but I like to adjust the opacity value so it looks like this: def a_water (expr p) = T:=identity; enddef; # no drawing of water color map-fg [80 80 100] -> http://www.staven.no/cavetest/testcave_elevation_4.pdf (NB You won't see the difference in Adobe Reader, but it shows up in SumatraPDF) Is there any way to adjust the opacity value when setting a transparent color? Or should I do this another way?