That makes sense.

Two comments/questions.

When I was a new user I had difficulty obtaining a LRUD envelope, because by default it is white on a white background. 

You have to know to include a statement like;

  colour map-fg [97 86 38]  # yellow brown

or

  colour map-fg 90  # grey

to get a meaningful pdf output.

Perhaps for the case where there are no scrap drawings, Therion should detect when the user has not explicitly set the map-fg to match the background, and when ‘walls on’ or ‘walls auto’ is set, then it could make the LRUD envelope a slightly different colour to the background?

Or an easier option, if therion detects that the background matches the foreground, issue a warning, say <centerline map-fg matches map-bg.  Adjust layout colours to make LRUD envelope visible>?

And the second question, for those people who like to see a thin line bounding the LRUD envelope (or even a fill pattern-not me, but the question has been asked in the past), perhaps a metapost hack to change area dimensions would work?  (I should just try it instead of asking the question I suppose – too lazy for now)

Bruce

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From: therion-bounces@speleo.sk [mailto:therion-bounces@speleo.sk] On Behalf Of Stacho Mudrak

This symbol is used to export centerline LRUD envelope when you have map created from survey centerline.

Basically, you can just set color and visibility of this symbol.

S.

On 13 November 2012 08:21, Bruce <bruce@tomo.co.nz> wrote:

I notice in the Therion source metapost there is an ‘area dimensions’.

It seems to be a clone of ‘area bedrock’, but perhaps there is a more cunning purpose?

What is it for and how is it used?

Bruce