[therion] Re: Help - my cave is inside-out

Martin Budaj m.b at speleo.sk
Wed Jan 5 22:44:40 CET 2005


Wookey wrote:

>> I have a bit of a problem with your example fix. Now the wall does not
>> follow the wall on my survey - I have had to distort it a little to solve
>> this problem. This seems to me to be the wrong answer - the original
>> version
>> is a correct drawing of the cave, therion needs to be able to join (and
>> distort if necessary) that drawing without telling me it it 'wrong' and I
>> have to draw the cave a slightly different shape in order for it to be
>> accepted.


There is a problem that therion does some calculations itself and some
lets to MetaPost. When the scraps are joined, therion has no idea if the
border is intersecting itself. When MetaPost examines the border, it's too
late for changing the scrap distortion -- it may only give a warning.

>> I realise this may not be easy, but I don't really think that telling the
>> user their correct drawing causes an error is good enough. Perhaps when
>> the
>> outline intersection happens on a line that is a scrap end line (i.e one
>> that
>> therion invented, not one the user drew) then that should not be an error


It can't be just ignored, because metapost needs non-intersecting outline
to determine the interior of scrap correctly.

>> and therion could adjust its own line to compensate? Is that practical?


It can't right now -- the intersection is detected only in metapost. We
would have to implement the algorithm in therion, which would be not
trivial.

Martin





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