Overlapping "fill to next" areas on a graph?


I have 4 lines of the same slope but with different offsets. For visualization, lets say they all have slope 1 and the offsets are +1,+2,+3, and +4.

I would like to have 2 areas of the graph shaded, so shade the region between the +1 and +3 offset lines and between the +2 and +4 offset lines. When I do this with "fill to next", the overlapping region between the 2 areas is simply overwritten by one or the other segments. This happens with a solid fill or pattern fill. Is there any way to do what I want to do?

Thanks for any help!
Since the current Igor version is incapable of rendering transparency (or other ways of blending for that matter), you have to take care of the overlapping area manually. What would you like to achieve for the overlapping area? Do you want to see an effect as if the colors of the two areas blend into each other? Anyway, you would have to set up a pattern to fill the areas between +1 and +2 as well as +3 and +4. Then set 'fill to next' separately for the +2 to +3 area, using a different fill to simulate what you want to achieve. If it's color mixing, then just select a color which resembles an intermediate between the colors of the top and the bottom area.
If you execute
ModifyGraph patBkgColor=2
the background of fill patterns will be transparent. Then the crosshatch patterns, for instance, will show what's behind between the crosshatch lines. Not real transparency, but better than nothing and may be good enough.

John Weeks
WaveMetrics, Inc.