3D capture of historic costumes at Helston Museum, Cornwall

Sign reading "3D scanning project. Thanks to Cornwall Museum Partnership with funding from Arts Council England we are learning how to 3D scan our collection"In December 2017 I was asked by Helston Museum to train staff and volunteers in how to use photogrammetry to record their historic costume collection in 3D. The costume gallery had closed and become a much-needed storage area. They decided that online 3D models, and possibly through screens in the museum, would be an interesting and engaging way to present the costumes now in the museum stores. They could record and display many more than there has ever been physical gallery space for.

The best way to capture the costumes is, of course, to use a mannequin. This would allow the costume to be viewed in the way it would have been worn, and rotated and viewed from any angle, an advantage over traditional static photographs. They would use Sketchfab to display the results.

Helston Museum decided to try the project in a very public way. Training was conducted in their temporary exhibition space, with panels explaining what was going on to the public. Projectors were used to display the results, as they happened. Staff and myself were on-hand to answer any questions from the public.

Over the course of a week, I trained both permanent staff, the Director and Assistant Curator, as well as a group of volunteers. They were shown how to light the mannequins, how to photograph them for 3D photogrammetry, and how to process and clean the 3D data on one of the museum’s existing PCs.

A volunteer photographs the dressed mannequin from every angle to ensure good coverage for photogrammetry
A volunteer photographs the dressed mannequin from every angle to ensure good coverage for photogrammetry

Some volunteers were more interested in photography, others in costume handling, and others in data processing and editing. I worked with their strengths, and the museum now have a great team to take the project on themselves. I remain available for questions from the team, and hope to teach some more advanced methods as they gain experience and confidence with 3D digitisation.

Helston Museum are Cornwall’s first museum to create a Sketchfab account, where they will share the results of this ongoing project. Visit Helston Museum on Sketchfab.

 

Hendraburnick ‘Quoit’ – the most decorated stone in southern Britain?

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Last year (2016) I was asked by Dr Andy Jones from Cornwall Archaeological Unit to record and study the surface of Hendraburnick Quoit on Bodmin Moor in Cornwall. The work, funded by Cornwall Archaeological Society, involved detailed 3D recording of the surface of the two stones that comprise the monument (which isn’t actually a quoit, more a ‘propped stone’). It was a complex task for which I used photogrammetry as the 3D scanning method. It involved careful planning and then taking many hundreds of high resolution photographs to guarantee coverage at an even resolution across all sides of both stones to enable careful study with millimetric levels of accuracy.

Our research was covered in the Telegraph who used the curioisty-grabbing headline “Ancient stone monuments may have been used for mysterious moonlit ceremonies, say archaeologists“. A full account of the project and our interpretation of the site can be found in the article Hendraburnick ‘Quoit’: recording and dating rock art in the west of Britain in Time & Mind – the “Journal of Archaeology, Consciousness and Culture”.

Analysis

After processing the 3D data I began the lengthy task of analysing the surfaces in great detail. Each potential feature was subjected to four checks using alternative methods, including virtual RTI and cross sections. I burnt a lot of midnight oil ensuring finding ‘cup marks’ and tracing the grooved lines that connect many of them together. I found 105 cup marks and 47 possible grooved lines connected or radiating from them, following the slope of the stone. This suggests that the lines were made in-situ rather than before the stone was moved in prehistory to its current location. This makes Hendraburnick Quoit the most known decorated or deliberately marked stone in southern Britain – possibly topping even Stonehenge in number of human-made features (152) on its surface.

The result was this plan:

Plan of cup marks on Hendraburnick propped stone
Cup marks on Hendraburnick propped stone

A very reduced resolution model of Hendraburnick can be viewed on Sketchfab, to aid understanding of the monument.

Recording St Piran’s Oratory – 3D model and animation

I have now completed my recent work on St Piran’s Oratory on behalf of St Piran Trust and Cornwall Archaeological Unit. It was a challenging task requiring a huge amount of computer resources and time, with colleagues at Archaeovision helping when my computer broke down, but I am pleased with the results.

Here is a short animation of St Piran’s Oratory, digitally freed from its concrete walls:

Here is an interactive model which you can zoom, turn, and inspect:

[sketchfab id=”f2f60441723f433cb230153768cf5f77″ start=”0″ spin=”” controls=”1″]

And here is an interactive 3D model of the complete Oratory structure with the concrete walls we see today:

[sketchfab id=”b360da3fe0ca4deda9d6d8b03e2cb4cf” start=”0″ spin=”” controls=”1″]

We must now wait for the final report by CAU (to which this data contributes) to better understand the building and its phasing. Watch this space.

It’s All About The Photos

It’s been a busy time for me recently, with much of my recent work focussing upon historic photographs and photogrammetry.

I have been working with the Morrab Library in Penzance to build a digitisation facility so that they may begin, with a volunteer workforce, to scan their wonderful collection of historic photographs. There are about 12,000 photos in the collection, ranging from 19th century glass plate negatives, to recent prints covering the whole of Cornwall. I have collated their Microsoft Works databases (one for each collection) into a single database, undertaken a data cleaning exercise, and mapped fields into Dublin Core metadata element set. The entire database was then imported into Omeka which is running on a local web server. I have tweaked Omeka and the environment in which it runs so that large TIFF files (up to 1GB) can be uploaded, with JPEG derivatives being created, the original TIFF being stored on a different server (separate from Omeka, with dual redundant disks and external backup) with the original filename (the photo’s accession number) being preserved. You can’t be too careful.

Whilst it isn’t designed out of the box to be a cataloguing tool, Omeka is doing exactly what we need. The user interface is well-designed and sufficiently easy for some elderly people to grasp quickly. The customisation to store unaltered original scans on an abstraction layer works well. Automatic database backups are also placed on the same server.

I have also begun working for an organisation called Azook, where I am the Project Officer for a project called MemoryFish. It will collect unpublished historic photos, films and recordings from private collections, documenting the history of the fishing industry in Cornwall. The initial areas are Falmouth, Newlyn and Newquay, and photos will be published on cornishmemory.com.

Then there’s the digital archaeology. I have been working for Cornwall Archaeological Unit and St Piran Trust on the recording of the now fully excavated St Piran’s Oratory. With the help of colleagues at Archaeovision we have processed a point cloud consisting of nearly 300 million points. This project is ongoing, but here is a taster of the work in progress.

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And in other news, in December 2014 I walked into a hairdressers and came out with short hair. It’s the shortest I’ve worn it since I was 17. Here’s the evidence.

Tom with short hair
Tom with short hair

And I’ve retired my famous trademark brown velvet jacket, replacing it with…. an almost identical copy. Some things should never change!

Carwynnen Quoit

Earlier this year I was commissioned by Sustrust to digitally reconstruct the then-collapsed Carwynnen Quoit, a neolithic dolmen, using existing 3D laser scan data. This would be used to inform the physical reconstruction of the monument. I was also asked to investigate and report on a number of stones adjacent to the quoit which were thought to have been worked or decorated in antiquity.

The ‘rock art’ panels (a mixture of natural and hand-made lines, not necessarily as part of a single deliberate piece) were recorded in 3D using Structure from Motion (SfM) photogrammetry.

On summer solstice 2014, the capstone was lowered into place by crane in front of hundreds of spectators, marking an end to a four year project.

The graphical output that I produced was used on leaflets and publicity, as well as extracts from my report on the potential rock art. Below are some of those images, used with permission.

Carwynnen Quoit reconstructed from laser scan data, placed upon the excavation plan

Carwynnen Quoit reconstructed from laser scan data, placed upon the excavation plan

One of the images created for the analysis of the 'Coffin Stone' close to Carwynnen Quoit

One of the images created for the analysis of the 'Coffin Stone' close to Carwynnen Quoit

Visit the Giant’s Quoit website to find out more about the project.

The Mermaid of Zennor – a low-fi 3D scan

The Mermaid of Zennor. A render of the 3D model to show detail of the carving.

Illuminance (occlusion) render of the low-resolution 3D model of the Mermaid of Zennor

At the weekend I had the chance to visit the church of St Senara in Zennor, Cornwall. I spent some time looking at the wonderful medieval carving of the famous mermaid. Despite not having my Canon DSLR with me, I decided to take a series of photos with my iPhone 4S (8MP) with the view of trying to reconstruct a low-resolution 3D model using photogrammetry to see how well opportunistic captures might come out. After processing the data, I managed to extract reasonably detailed geometry, with just over a million vertices (points) after cleaning the data up (removing unwanted elements, removing stray points). A bit of processing and I was able to produce the above image to show some nice details on the carving. The mermaid looks quite different to my eye. Below is a render using a directional surface filter. The data is a very long way from being perfect, and I was unable to take any measurements to scale and check the accuracy of the geometry. However, the results are very usable for interpretative purposes, especially given the nature of how the underlying photos were captured – by hand on a 2.5 year old iPhone.

Render of the 3D model of the Mermaid of Zennor, using a directional material.

The following image is a ‘depth map’ of the Mermaid, where black is far and white is near. Can you see a hint of the Mermaid’s face? Scroll down to see an embedded 3D model (latest Firefox, Safari or Chrome browser recommended).

Depth map of the low-resolution 3D model of the Mermaid of Zennor

[iframe width=”100%” src=”http://studio.verold.com/projects/53a9836fc55d9602000007cd/embed”]

Recording St Piran’s Oratory

For the last couple of weeks, and on St Piran’s Day itself, I have been helping out with the Uncovering St Piran’s Oratory project. Organised by St Piran Trust and run by Cornwall Council Historic Environment Service the project aims to uncover as much of the (potentially) early medieval structure to assess and record its condition.

Following a 15-year-campaign, the St Piran Trust plans to unearth and conserve St Piran’s Oratory, believed to be amongst the oldest Christian buildings on mainland Britain. The site has been of central importance to Cornish people for over 1,400 years as a place of worship and pilgrimage, and as a focus for cultural expression. Today, many hundreds of people gather at the site annually to mark St Piran’s Day. The saint’s flag (which features in a stained-glass window installed in Westminster Abbey in 1888) – a white cross on a black field, is flown the length and breadth of Cornwall.

The scheduled ancient monument is a listed building and was buried in 1980, for “its own protection”. Since then expert opinion has shifted, amid calls for it to be uncovered and conserved in a more sympathetic way.

The Oratory and associated protective concrete structure from 1910 are protected as a Scheduled Ancient Monument. Unfortunately in 1980 as part of the burial programme, the concrete roof was removed – or so we thought. During this year’s excavation we found that part of the roof structure, badly damaged and sitting at an angle, had been left where it fell and simply buried. It has been decided that the pile of broken concrete needs to be removed to safely continue with the project.

Concrete at St Piran's Oratory

I have been commissioned to record concrete remains in-situ using photogrammetry to complement more traditional recording. I undertook the photography aspect of photogrammetric recording on St Piran’s Day (5th March 2014) and am now processing the point clouds. This will result in a highly detailed model of the concrete remains, which include a buttress, part of the reinforced concrete curved roof, and the hollow mundic blocks used to construct the walls.

From a technical point of view it is proving to be a challenge. There is no uniformity to the concrete remains – it is full of overhangs, pockets and voids. The photographic capture strategy was tough to work out, and 16GB of RAW images were taken after careful cleaning of the concrete by trowel, hand shovel, bucket and brush. I have covered as many angles as was safe and practical to do so.

I will be delivering the point cloud and a series of orthographic views to the client.

Once the concrete has been removed, it is hoped to expose more of the Oratory, and I will be able to record the medieval structure in the same manner.

In the meantime, I have the opportunity to get out in the open air and dig, which I love.

The are plenty of photos on the open Facebook group Uncovering St Piran’s Oratory. You can also see a 3D model of the excavation as it stood on St Piran’s Day 2014.

Reprocessing the St John the Evangelist data from Gulval

Since first posting about the images of the Four Evangelists found on the medieval cross-base at Gulval Church, I have been striving to produce clearer images of each saint for inclusion in a publication. The image will only ever be as good as the condition of the stone allows, but it is possible to wring a fair amount of detail from the monument through digital means.

The most difficult image of the Evangelists on the Gulval stone is St John. Depicted as half man, half eagle, his side of the cross base is damaged and worn, especially at the top. The details which I would like to further enhance are the eagle head, and the book he is holding in his hand. This is the only side where the lettering is far from clear, and many people remain to be convinced that there is indeed an “IH” (Iohan) carved on it at all.

As many archaeologists do, I have become rather obsessed with this image. When processing data of this nature one does have to be very careful in the interpretation, and not see what one wants to see. Part of my ‘therapy’, if you like, is to blog about the results as I go.

So, I have re-processed the photographs of the east side of the cross-base using the highest level of detail that my computers will allow, adding in some extra angles which I did not use in my initial images, to try and capture further detail at the sculpture’s head level. The processing took from about 7am until 6pm. After some tidying of the data (and a fair amount of quiet wishing that the computer wouldn’t crash), I produced a 1.7GB point cloud ready to inspect.

The use of false colour can be really useful, as it affects one’s perceptions of the data. Good for ‘getting your eye in’ to the data, and the shapes of the carving.

So without further ado, here are some renderings of St John with his Symbol’s head (the eagle). Can you spot any vertical lettering on his book? Fellow digital specialists please note that this is still rough data!

gulval2-east-ambient-occ-1024-128s-bw-hicontrast-ortho-high
High contrast ambient occlusion.
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Greyscale ambient occlusion.
gulval2-east-ambient-occ-1024-128s-red-yellow-ortho-high
Ambient occlusion using red and yellow colouring
gulval2-east-ambient-occ-1024-128s-redwhite-ortho-high
Ambient occlusion using red and white colouring.

 

A Medieval Discovery at Gulval Church, Cornwall

Gulval Cross-BaseJust to the left of the south porch of Gulval Church, near Penzance in Cornwall, lies a large block of granite. I first came across it on a visit to the churchyard in 2012. However, it really piqued my interest a couple of months ago after reading a short report in Newsletter 132 of the Cornwall Archaeological Society. The article, entitled ‘An unusual stone at Gulval Church‘, by Professor Mick Aston, Teresa Hall, Professor Rosemary Cramp, Ann Preston-Jones and Andrew Langdon, highlighted that the block was a medieval cross-base, and was decorated on all four sides. Aside from the south, pictured here, the images on the other sides were very difficult to see at all. Ann and Andrew visited the stone at night “armed with car batteries, a mirror, two spotlights, a tripod, head torches, and a camera” to capture raking light photos of the decorations to see if controlled shadows could be used to interpret the decorations.

The results were good, producing a set of shadowy atmospheric photos of each side. Professor Cramp began to interpret the scenes from these photos but noted that, while useful, the photos only provided a single fixed view, and she had not seen the cross-base with her own eyes. It was thus difficult to say for sure what was depicted on this rough stone.

It was shortly after receiving the newsletter that I also heard the sad news of Mick Aston’s death. Doubtless that Mick would have had a continued interest in the cross-base, and given that I only live a few miles from the church I became determined to use the tools available to me to record the cross-base and see if I could help with the interpretation.

On 8 June 2013 I visited Gulval Church and recorded in high resolution 3D each side of the cross-base using a photogrammetric approach. Taking a series of over a hundred overlapping 18 megapixel scale photos at a fixed focal length, I covered the whole block.  It was quite a tricky subject to tackle, as there is very limited clearance between the cross-base and two of the church walls.

Over the next few weeks, I began to process the images into 3D point clouds, and from there to solid 3D meshes. Afterwards, I subjected each side to a series of techniques which I have used to analyse prehistoric rock art and inscriptions in the past. The results were fantastic.

What is depicted on the cross-base?

Thanks to this analysis, I believe that we now know what is shown on the cross-base at Gulval. The existing interpretations, as laid out in the CAS Newsletter, didn’t match up with what I have found. The computer-generated images, shown below (and may others that I have created using false colour representations of depth), have been able to provide a slightly clearer representation of the granite carvings, and, I believe, help perceive them in a different way. I can now see many of the details in the original photos now that I know what I am looking for.

Rather than sit on this discovery for ages until everything is just right, I have decided to post my initial findings here. It does not represent a full description of the findings and condition of the cross-base and its imagery, and it builds upon the work already done.

Firstly, I must thank my friend, Nick Ford, for putting me onto the iconography – I believe that he spotted what was depicted in the first image I showed to him straight away, and knew what the others would reveal. It led to an exciting evening searching for comparative images, and further enhancing them. And without the original report in CAS Newsletter 132 (now online) I wouldn’t have got this point at all.

The cross-base depicts the four Evangelists, Matthew, Mark, Luke and John, as the four living creatures described in Ezekiel 10:14 and Rev 4:6-7

Revelation 4:6-7

New International Version (NIV)

6 Also in front of the throne there was what looked like a sea of glass, clear as crystal.

In the center, around the throne, were four living creatures, and they were covered with eyes, in front and in back. 7 The first living creature was like a lion, the second was like an ox, the third had a face like a man, the fourth was like a flying eagle.

The Gulval Four Evangelists

The south side of the stone depicts St Matthew. He is symbolised as a winged man or an angel, and depicted here with a halo, holding a book (Gospels or Book of Life?) with “MT” inscribed on it. The lower part is damaged. This image shows the details picked out using an ambient occlusion filter.

On the west, facing outwards, is St Mark. He is shown kneeling, with haloed lion head. His book, held in his left hand, has “M” on it. It is possible that he is giving the sign of benediction with his right. The folds of his robes are nicely visible.

On the north, facing the church proper, is Luke, depicted here seated with haloed calf head . His book, held in a rather large left hand, has “LS” on it (Lucas). Luke is mainly depicted as an ox, but it isn’t unknown for him to be shown as a calf.

On the east, facing the porch wall, perhaps the most badly eroded of them all, is St John, depicted as the eagle. His robes, especially the folds around his legs, are clearly visible.  It is difficult to discern the presence of any halo. He is holding a book in his right hand, with what looks to be an “H” on it (not easily visible in this image – only range-colouring a very small area shows this). It would be very neat if it said “IH” – Iohan, but archaeology isn’t always a neat discipline. Further work needs to be done here.

We must remember that the stone block onto which these images are carved is a course Lands End granite. Some of the quartz crystals are several centimeters long – fine detail just isn’t possible – and granite can crumble when exposed to the elements.

A Tetramorphic Cross-Base?

So there we have it. Starting on the south side of the stone, if you run the sequence clockwise (South, West, North, East), runs the familiar sequence of Matthew, Mark, Luke and John. Matthew, the best preserved of all, was positioned facing outwards, and the shield-like shape of the carving has, according to some, become thought to be a coat of arms. Now that we know what is really shown here, perhaps we can even call it a tetramorphic cross base, bringing together the symbols of the Four Evangelists together into a single object. One thing is for certain, however, and that is a lot more work needs to be done on the Gulval cross-base, in terms of research, verification, and recording techniques. Reflectance Transformation Imaging (RTI) will certainly be the next approach for further enhancing the panels. Comparative examples need to be sought.

This could have a big impact upon our understanding of Gulval, and indeed have ramifications on how we understand the history of this part of Cornwall in the early Middle Ages.

The authors of the original article in the CAS Newsletter have had copies of the images and my findings in advance of this blog post. Luckily, when I sent my findings to Ann Preston-Jones, she was pleased, as she felt that these were the Evangelists, but lacked firm evidence to back it up. I trust that my arguments, and the images above, will help to win around any doubters.

I have been asked to add the finished images of the Evangelists to the forthcoming Corpus of Early Cornish Sculpture, to which I am honoured to be able to make a contribution. The vicar of Gulval Church is adding the images to his parish newsletter. Who knows, even a sermon may come of it!

Further images and information will be added to subsequent blog posts, and linked from here, so do bookmark this page and check back from time to time.

And now for the plug!

As an independent archaeologist, I am of course pleased to offer my professional services. Please contact me with any enquiries.

Below is a series of images of St John (Eagle) from the east side of the cross-base. The 3D data has been filtered in a number of ways to extract the detail of the carving.

East elevation of a medieval cross base at Gulval, Penzance, depicting St John the Evangelist as an eagle (see Rev 4:6-7 & Ezekiel 10:14). Captured using photogrammetric methods and processed using different filters to interpret the carving.