[Therion] Wall visibility affecting lox model

[Bruce]

>KML looks fine, as does the lox model.

>I understand that the pit would look like a transparent hole if
>rendered in a map without the lower scrap. Wasn't there are way you
>suggested which might allow toggling the options on a line in
>different maps Bruce? So you could have the pit filled in one map but
>transparent in another?

Yes, the revise statement would allow the user to quite easily change the
outline parameter for any 'non-standard' outputs without having to manually
edit it each time.  

If the pit is defined in scrap1 as Martin suggested ('-outline in -clip
off' or whatever is required) and it has -id scrap1pit1,
then perhaps in the map definition with the lower scraps offset, the revise
statement could be included...

map LowerScrapOffset -proj plan
   revise scrap1pit1 -outline none          # restore shading to top scrap
   scrap1 at s1
   MapofScrap2 preview 100 000 metres below # MapofScrap2 contains scrap2 at s2
endmap
 
Must admit I've not used revise in this context, and not sure if revise
would need to be inside the map definition or out.  Still, one way or
another it should work and be relatively painless unless you have 400 pit
lines to revise.

To digress a little...
If your resolution was not as seamless as it appears to be I was going to
cancel my support of the -2d [in out] and -3d [in out] idea and suggest a
new entity;

area void

Area void would have no effect in 3d models and would erase the passage fill
in 2d drawings (and as a nice to have bonus- except where no scrap is
rendered beneath it in the particular output).  
It seems there is no need though.

Bruce