[Therion] xtherion - Multiple background sketches

[Bill Gee]

A week ago we had two teams of surveyors working in some very tight side areas of a cave.  In the end we discovered that it was all one room.  We came away with at least five pages of sketch depicting various areas of the room.  It is probably not complete ...

Doing a join on room sketches like this is probably not possible.  Some of the sketches don't have any wall, and for two of them the wall is only along one side.  I think I need to some up with some way to do the whole room in one scrap.

In this case the sketches are all the same scale (1 inch to ten feet), and I rotated the scans so that north is the same direction on all of them.

In xtherion I see that multiple background images can be brought in to a single th2 file.  I tried it and did not immediately see what I want.  So my questions to the group ...

1) Is there a way to drag/drop reposition a background image?

2) Is there a way to make images transparent?  I tried fiddling with the gamma slider but it did not do anything for transparency.

3) Is there a way to crop off arbitrary sections of a background image?  Some of the sketch pages also have cross-sections, and those will seriously confuse things when trying to place objects.  I would like to crop them out.

4) Is this something that I need to do in an external image editor like Gimp?  I have not used Gimp in several years.  The learning curve is daunting.  

Thanks!
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Bill Gee