I eventually solved my problem by making sure the line segments overlapped, rather than joining at a single point. After checking that they did indeed join at a single point, as below. I presume the missing area was due to some kind of rounding error making Therion think that the area bounding lines did not form a closed area. Only manifesting at some scale(s). Bruce From: Bruce Mutton <bruce@tomo.co.nz> Sent: Monday, 16 October 2023 18:22 To: 'List for Therion users' <therion@speleo.sk> Subject: Area water visibility inconsistent depending on scale Hello again I'm wondering why my area water displays at scale of 1:1000 but if I compile at 1:500 just one of the area waters does not display? The two water areas are both defined in the same scrap, which I have highlighted in yellow in one of the images. The areas are defined by three lines - a single horizontal line for the water surface and two curved lines to bound each of the areas. All lines and areas have -clip off set. When the lower curved lines have -visibility on, I can see they are there, but the area water still does not display. Thinking that the label about the water supply might be somehow obscuring the area, I deleted it, but that had no effect Other area waters in the same compilation (indeed the same entire project) are OK as far as I know. Have never noticed behaviour like this before. Therion 6.1.8 Images below. I've checked the distortion with debug first and debug second, distortion looks OK, but there is no sign of the larger area. With lower area water boundaries set to -visibility on. I'm wondering if the morphing is shortening the top line at 1:1000 (making the area fail) but not at 1:500. I don't think this should happen, as I made the left-hand line points coincident, so both area boundary lines should join perfectly without a gap. It seems they do, as below. So any ideas as to why visibility of one of the area waters in this project should be scale dependant? Thanks Bruce