December 2023 Challenge: 3D Glastonbury Tor

[Redrobes]

Well I appear to have guessed the challenge clue correct for a second month. But this month I might actually have a go at making a map.

I have had a good think about it and realize that the obvious solstice map is for Stone Henge but I will leave that one to another entrant and concentrate on Glastonbury Tor. I am sure the world knows of Glastonbury Festival where there is an annual arts/music festival every year and attracts about 100K people and is a bit of a big deal in the UK. That festival occurs in Pilton a few miles away but often in the background of the shots of the band at the Pyramid stage you can see the Tor in the background.

The Tor is a prominent hill lying in lowland area known as the Somerset Levels. So it sticks out quite a bit and is a well known UK landmark. It is said (by those of a certain persuasion...) that there lies lines of power that emanate from the Tor and connect to the other historic landmarks like Stone Henge. These are known as Lay Lines and make up a web of interconnected lines of power that the ancient people used as part of their worship.

The Druids make up one of many alternative faiths in Glastonbury Town and there are a few days of the year where there are processions of various nature. But on the Solstices the Druids pass through the town high street and proceed up the Tor for usually the Sunrise but also the Sunset too. Lots of people gather up there on those days and its quite a lively place to be.

I could just make a map of the Tor or the Lay Lines but they have been done to death. What I would like to try and have a go at is a 3D model of the Tor hill. I could do my usual 3D stuff virtually using graphics but this time I would like to make one in Paper Craft style.

If anybody has been paying attention to my filters its obvious that I have a paper laser cutter which I have built myself and trying to debug for the last few years. But its working great now and I can make cards and paper craft with a lot of precision. The difficulty would be what cuts to make in order to make a 3D Tor.

So thats my challenge. Its an unusual map and probably not one which might win but I need the impetus to have a go and because its December where there might be some time over the Christmas area when I will have some free time I think I have the chance to try this out.

My intent is to make some cuts in lines like contours in one sheet and pull up the peak of the hill and see whether the cuts allow the paper to expand and the amount, position, spacing and shape of cuts will restrict the paper movement in order to form the shape. It might not work but I would like to see if that is possible. So some of the initial phase might be to try some test cuts and see how much slope I get with different spacing and styles of cuts. If that completely fails then there is the fallback of cutting out polygons and gluing them all together but thats a lot of effort and it would be nice to be able to go from sheet of paper to 3D model in one process.

Wish me luck cos I think I am gonna need it. Normally I have a good idea of how to make the result but this time there is a lot of ambiguity and potential for complete failure !

[waldronate]

Are you going for contour-sliced and laminated or more of a single-sheet fold-up kind of thing?

Ah, reading comprehension. I need to work on that.

Getting the radials sliced out of the sheet without tearing at the top will be the hard part, I would think.

[ChickPea]

This sounds really interesting and I'll be curious to see how you get on. Even if it doesn't quite work out, it'll still be a good learning process and I feel the Guild challenges are all about experimenting and trying new things.

[- JO -]

I really like the experimental, artisanal aspect of your project. I'm looking forward to seeing how it turns out.

[Straf]

I really like the experimental, artisanal aspect of your project. I'm looking forward to seeing how it turns out.

Providing the homemade laser doesn't open a portal into another dimension.

[Ifrix]

This is such a cool idea - excited to see how it turns out!

[Redrobes]

Made a bit of start.

I sketched out the contour lines from various maps I could find of the place. There was a bit of guess work in some places as I could not find a map with all of the contours in isolation. Maybe there is a DEM lidar model of it somewhere but if so then I don't have one.


There has been a few posts I have done about this but its my usual method. I clean up the contour lines and fill them in a zebra pattern. Then you have to make sure that the bands don't overlap at all and also that the rough widths of them are about even. You can do this by blurring it and using the colour curves feature of a paint app to adjust the contours to thicken or thin them up. Once happy, whack the contrast up to max to make it just two colour and then use the fill tool to fill in each band.


Once you have a nice set of zebra stripes count from the the top of the map to the lowest point. That for me was about 30 of them. So I chose to go up in steps of 8 greyscale amounts so that it goes from pure white down to nearly black.


Then a smooth in paint app softens up the wedding cake effect.


That in 3D looks like this - which basically looks about right at first glance.


Its still got some ripples in it because smoothing in a paint app is still done with each pixel in a byte. But ill smooth it a bit more later on in my 3D app which keeps the height in floating point format so it will get rid of them. Once I have done that I will scale it so that the heights are real world based so that the Tor is 157m high.

Before I start making cuts into paper I think ill start with some circles and do a variety of gaps and see how it handles it. The rough pattern is something like this:


So the idea is that as you pull up on the top circle then the contours split apart and are joined up by the tabs not cut. Each pair of contours will make a diamond shape and multiple layers will make a diamond pattern a bit like a wire fence. Hopefully with enough cuts then it will stretch apart and not deform the shape too much. I have to find cuts so that the shape can pull up and therefore increase its surface area whilst at the same time the structure came from a flat sheet of paper which is not changing its surface area so its filling in the new area with air. But it might pull in a bit.

There are some materials which increase in volume when stretched. These have a negative Poisson ratio and are known as Auxetic materials. What I need to do is cut the paper is such a way as to have a zero Poisson ratio or hope that with thin enough cuts it can get close to that. I am kind of expecting that I need to make some bits of it have close to zero and some have negative and then it will stretch up. So yeah not sure how that is going to work out !

Most of these negative ratios depend on cutting a zig zag lines so that when pulled it uncompresses like a spring and expands.

So the first thing to cut are some circles and see if I can get them into a cone shape and whether the sides pull in or out.

If that works out then I think its just a case of applying it to the 3D model in areas with cut density based on the 3D model slope.

[- JO -]

Good job ! It really looks nice !

[Straf]

Dunno if you are aware of this site https://magic.defra.gov.uk/home.htm

At certain zoom levels you can get reasonable contours.

[Redrobes]

Thanks for all the comments.

I had not seen that defra site before but its not appearing properly on this machine as I cant ever seem to get arcgis style maps to work on the browser. I used to have the whole UK lidar link somewhere but its been so long since I used that I have lost the link.

I am just checking the accuracy of the height map and I found some pictures online like this one:
https://live.staticflickr.com/3191/2...c831d2b6_b.jpg

And positioning my height map to match I get this:


which I think is close enough. You can see on the photo that the Tor has these steps in the ground height. I am not sure why this is but normally its where ancient people have constructed palisades of wood but the Tor does not seem to be large enough to offer a village settlement on top. But maybe it did as part of a larger settlement where the town is now.

I am intending to only pull up the Tor hill and not all of this surrounding landscape. So at some point I might have to add in some of these steps.

Looking at these auxetic materials which have been cut by a laser they all seem to share the same sort of property in that they have spots with arms cut so that when stretched it allows the arms to expand or unfurl. I think its just a case of making the cuts to control where the height can be obtained and how much resistance or springiness the paper will have when pulled. If that can be controlled then maybe its not quite such a tall order to make it. The software to calculate the cuts still seems quite tough tho.

So zig zags like this: