Interesting John With your model as posted I did not get dual tubes with walls off although I did with walls on. If you remove all of the point passage-height and point dimensions from your scrap, then the behaviour of your model seems to match the behaviour I described. BTW I added my previous post to the wiki examples page http://therion.speleo.sk/wiki/doku.php/examples#loch_models_paperless_survey _plan_scraps_and_lrud Not able to spend more time on this just now (winter sniffles-back to bed), but seems like point dimensions and point passage-height changes the behaviour. A semi automated way of enabling therion to produce accurate model passage heights using splay shots would be useful, and it seems like Footlegs proposal might be convenient (for those of us who don't have to write the code). Bruce _____ From: therion-bounces@speleo.sk [mailto:therion-bounces@speleo.sk] On Behalf Of John Stevens Sent: Wednesday, 24 July 2013 7:03 a.m. To: 'List for Therion users' Subject: Re: [Therion] Loch passage tube behaviour Bruce a very useful article but it differs from my experience in a couple of ways. I thought a couple of months ago I would try and produce a reasonable 3d model of a cave. So I surveyed a short section of passage with more data than I could possibly normally use. I set stations at 5m intervals and took 8 wall measurements every 1m. This would get me a lot of splays that I could then use as vertices for a 3d model (if I could find/write some software to make the model, not done yet) I could then compare this model with the one Therion produces and see which extra splays are really needed. Unlike your models I seem to get the centreline tube in the middle (mostly) of the scrap tube. Unfortunately this centreline tube often protrudes through the scrap tube, ruining the model. How am I getting two tube? I have tried various options with walls on/off/auto or commented out, to no avail. I also found the Dimensions -value [up, down] useful but it sometimes does unexpected things. Passage Height was even worse for this. If a single number was given it distributed the measurement above and below the centreline. If + - was used it appeared on the plan but did nothing on the model. using Therion 5.3.11 This is a work in progress and your mail has come at just the right time Cheers John