Visualising confined interior scenes elegantly in Blender 3D

Final render: Reconstruction of the kitchens, Orford Castle.

I thought I would quickly pen this article having recently run into some awkward problems while tackling visualisations of some extremely confined interior spaces. I am sharing this in case it may help or offer some pointers to anyone else tasked with a similar problem. I am using my reconstructions of Orford Castle in Suffolk, produced for English Heritage, as an example here.

When setting up my 3D models in the Blender 3D software, the usual and most obvious way to fit most of the scene into the final image is to set a very wide angle camera lens. But the drawback with wide angle lens settings is that they tend to create a lot of distortion in the image which just doesn't look visually pleasing. So, I prefer to use longer focal lengths of between 40mm and 70mm but that means of course, that we won't get to see all of the room in the image. How did I tackle this problem, then?

Well, I cheated.

In Blender 3D, you can bend the rules somewhat. There are some nifty camera settings that emulate often prohibitively-expensive tilt-shift lenses which are used a lot by architectural photographers. Using a combination of camera rotation and adjusting the camera's X and Y shift values, it's possible to correct some of the distortion that comes with the wider angle lens settings. You can also play with the camera's sensor size and choose a setting that emulates a real full-frame camera - and even beyond that! But sometimes even this doesn't quite provide enough flexibility. So this is when it's time to roll out the big hacks.

When visualising Orford Castle's prison, I had faced the following challenges:


  1. I needed to show as much of the interior space as possible,
  2. The room is VERY dark - there is only one tiny natural light source,
  3. I needed to make the image very tall so that we can see how the prison was accessed via a rope-ladder and trap-door,
  4. I have to minimise the amount of lens distortion in the image to create a pleasing image,
  5. The scene needed to be accurately lit.
Positioning the camera inside the room with a wide angle of view resulted in this extremely distorted and completely unsatisfactory image.

 I decided quite early on with this scene that choosing a wide angle lens wouldn't work here. What I needed was a way to position my camera at a distance just far enough away from my model that I could use a focal length of 60mm-70mm to avoid distortion and fit in as much of the prison's interior space as I could.


To do this I positioned my camera well outside of the model and set its image dimensions to 2500 x 5000 px which will produce for me a nice, detailed render of the full prison space. But now I have a wall with a backface obscuring the view of the prison's interior. It might seem like a straight-forward task of just deleting or hiding the wall in the scene, but the problem is that this hides the wall from both the camera AND the scene. The environment lighting that I have set up to illuminate the room (through a small window) penetrates the room through the void left by the missing wall, which is no good at all.

The surprisingly simple workaround here is to employ Blender's Light Path material node which controls what elements in a scene the camera will see in the render. There are some good tutorials out there on the web which explain this very useful node in more detail, but for my example I am using the Is Camera Ray output of the Light Path node as the factor for mixing two of Blender's material shaders -  the Principled and Transparent shaders. This is making the obscuring wall transparent or invisible to the camera, but still visible to the rest of the scene so that lighting can be calculated accurately.

By positioning my camera some distance outside the room and using Blender's Light Path node to hide the backfacing wall from the camera, I could use a much longer focal length resulting in far less image distortion.

The final result of the render. The Prison, Orford Castle. Accurately-lit and no ugly lens distortion!

I used this same technique on Orford Castle's kitchens (image at top of page) - although in this example I did use a slightly wider camera focal length, with some distortion in the lower part of the image, it still gave some reasonably pleasing results.


Allen Smelt Mill visual reconstruction wins digital initiative and innovation award

Illustrated reconstruction of Allen Smelt Mill (1800s)

Two digital reconstruction images of Allen Smelt Mill and Allenheads Mineyard in the North Pennines have won the Association for Industrial Archaeology's Peter Neaverson Award for Digital Initiative and Innovation.


The two reconstruction images were produced by East Lothian-based illustrator Bob Marshall for an industrial archaeology interpretation project in the North Pennines.  

Bob specialises in producing high-detail visual reconstructions of historic buildings and monuments and was commissioned by Differentia Design in Hexham as part of their project for the North Pennines AONB Partnership to bring to life the history of the lead industry in the East Allen Valley in Northumberland.

Bob worked with Tim Crump, a Hexham based interpreter and ex-archaeologist, to turn the scant records and remains on the ground into an accurate representation of two important Northumberland lead production sites at the height of the industry in the mid-nineteenth century, and the images are now displayed on interpretation panels helping to explain the workings of the former industrial site to visitors. 

The panels were produced in long lasting natural materials using Lavastone. This material was chosen for its longevity and robustness as well as it environmental credentials. 

On receiving news of the award, Bob Marshall said: “It has been an enormous joy to create these engaging artworks to contribute to the understanding of our local industrial heritage. It was important to do our research carefully to get this absolutely right and the task of understanding and interpreting this complex site presented us with a difficult challenge. This fabulous award came unexpectedly, and it has made the great lengths we went to on this project even more worthwhile.”

At its peak in the 1850’s, Allen Smelt Mill was one of the largest lead smelting mills in the country and would have generated enormous wealth for the valley. The mill was demolished in the 1950s and 1970s and all that remains are flue openings, the ore hearths, the wheel pit and roasting furnaces which have only recently been uncovered. Bob’s approach to the challenge of reconstructing Allen Smelt Mill was to employ the use of three-dimensional computer models to help visually reconstruct the complex arrangement of buildings and flues.

Image: Detail – Allen Smelt Mill
Bob worked closely with Tim Crump of Wildlight and Steve Pardue of Differentia Design, both based in Hexham, to develop the images and the interpretive panels. With only limited visual references to work from, they carefully researched the mill’s history by extracting what information they could from books, old plan drawings and from some local knowledge. 

The project took several months to accomplish, and it is one of the most technically-challenging visual reconstructions that Bob has attempted. To achieve it, it was necessary for Bob and Tim to understand the lead smelting and refinement process in detail - a subject which neither of them had much knowledge of before they began work on this project. The task was made more complex by the fact that only puzzling fragments remain of the smelting mill. There are no records of its layout apart from a single plan drawing which shows its general arrangement and an indication of which refinement processes  were carried out in the different buildings. Some guesswork had to be employed to try to visualise the arrangement of flues which carried the highly toxic fumes away from the roasting furnaces and smelting hearths and connected to two, horizontal chimneys which end high up on the moors above Allendale, over two miles away. 

Image: Reconstruction of Allenheads Mine Yard
The Peter Neaverson award for Digital Initiative and Innovation recognises the impact that developing digital technologies are having on our interpretation, dissemination and conservation of our industrial heritage and archaeology and is given to the creators of the work which makes the most effective use of digital technologies in industrial archaeology.

Fiona Knox of North Pennines Area of Outstanding Natural Beauty (AONB), who commissioned the panels said: “This is fantastic news and so well deserved. People said it [the reconstruction] couldn’t be done but you pulled it off and so brilliantly. Everyone has been excited and loved the images on the panel.”

Bob Marshall and Tim Crump received the award at the Association for Industrial Archaeology’s conference at the University of Nottingham on 1 September and gave a short presentation explaining the processes and techniques they used to create the reconstruction visuals.

The remains of Allen Smelt Mill today showing the remains of the flue openings.
The remains of one of many refining furnaces.

A floor plan shows the layout of the former smelting mill
Computer 3D models were made to try and understand the mill's complex arrangement.

Detailed 3D models were made of some of the major pieces of equipment on the two sites. These are known as 'buddles' and were used for washing the lead ore prior to refinement.
Detail view - Allenheads Mine yard

Cutaway Detail - Allen Smelt Mill
AIA Prizewinners 2018. Bob Marshall (second) and Tim Crump (third) from right.

Further information and links: 


Allen Smelt Mill (Historic England) 

Bob Marshall – Illustrator & 3D modelmaker

Tim Crump (Wildlight)

Steve Pardue (Differentia Design)

Reconstructing Our Lost Industrial Past

Allen Smelt Mill and Allenheads Mine Yard


At its peak, Allen Smelting Mill was a noisy factory full of fire, fumes and smoke. It is rather hard to imagine such a scene when you visit the site today. Only puzzling fragments remain of the mill which in the 1850s, was one of the largest in the country. It had the capacity to process over 2,000 tons of lead ore each year and would have generated enormous wealth for this valley.

Illustrated reconstruction of Allen Smelt Mill (1800s)

The Smelting Mill was demolished in the 1950s and 1970s. All that remains are flue openings, the ore hearths, the wheel pit and roasting furnaces which have only recently been uncovered. The flues can be described as long horizontal chimneys, which end at chimneys high up on the moors above Allendale, over two miles away. The flue system here is the best preserved in England.

These illustrated reconstructions are the product of a close partnership between myself, Steve Pardue of Differentia Design and Tim Crump of www.wildlight.co.uk. With the help of local experts, we worked together to research and collate historical information from a range of sources including books, old photographs and drawings and written descriptions to help us reconstruct these two lead mining and lead processing sites. The task of reconstructing the lead smelting mill took us several months and is to date, one of the most complicated visual reconstruction projects I have attempted, requiring the use of 3D computer modelling to plot the locations of the various buildings, sheds and complex network of flues designed to carry the highly toxic lead fumes away from the site.

This project required us to research and understand the lead smelting and refinement process which is a subject I had very little knowledge of before embarking on this project. Smelting and refinement was carried out in different furnaces at Allendale. Roasting would prepare the ore for smelting; ore hearths would ‘sweat out’ pure lead from the ore; slag hearths would re-smelt slag from the ore hearths; and silver was refined from lead in the separating house.

The lead ore or galena, was transported to this factory from lead mines across the North Pennines, including that of Allenheads just a few miles up the valley and which I have also reconstructed as part of this project. At the Allenheads mine yard, teams of men and boys operated jiggers and buddles to sift and wash the mined minerals in order to extract every available ounce of lead ore. The process required vast quantities of water. The ore was then taken from here to the smelting mill at Allendale on the backs of small, rugged horses known as Galloways, then deposited into storage bays here called bingsteads, where the material would then await refinement.


Illustrated reconstruction showing the extent of Allenheads Mine Yard and Washing Floor (1800s)
Close-up of the Allenheads Mine Yard reconstruction
First, sulphur in the lead ore was burnt off in the roasting furnace and this prepared the ore for smelting. A coal fire at the front of the furnace was kept separate from the lead ore by a brick shelf or a 'fire bridge'. Heat was drawn through the furnace by the flues at the back.

A draught created by mechanical bellows powered by a giant central water wheel, kept the fires in the Ore hearths hot enough to slowly sweat the lead out of the ore. It provided the oxygen needed for the chemical processes to convert lead ore into lead. Tiny bits of the parent rock, including fragments of ore, were left behind as slag. This was crushed and smelted again in the slag hearths to recover any remaining lead.

Illustrated reconstruction showing a cutaway view of Allendale Smelt Mill. A central water wheel drives mechanical bellows which fed a supply of air to the factory's ore hearths. Fumes from the furnaces used to burn off sulphur and other impurities in the lead ore, are carried away from the factory by a complex network of flues.
A complex network of flues carried the toxic fumes away from the site but were also a way of ensuring every last bit of lead was collected. As the fumes cooled, lead and silver particles condensed on the walls. The mill shut down its smelting operations in order for this ‘fume’ to be scraped off and collected from time to time.

The final part of the lead smelting process was to separate out silver. Although it is only a tiny part of lead ore, its value still made it worth the effort of extracting. The silver was separated from the lead in a separate part of the mill by melting it in a line of pots, each about five or six feet across.

Detailed cutaway view of building where silver was separated from the lead by melting it in a series of pans.

As it melted the purified molten lead was ladled into moulds to cool into bars of lead called ‘pigs’ and were then transported down the valley to Newcastle, to be shipped to the rest of the country, or exported overseas.

My reconstructions are to be mounted on new interpretation boards and these will be installed on site at Allendale Mill and at Allenheads mine yard.

This is the only plan drawing we have of Allen Smelt Mill in the 1800s showing the layout of its buildings and the route of its horizontal flues.
The ore hearths and flue openings are all that remains of Allen Smelt Mill today.
The remains of a fire pit - which belonged to one of the many furnaces at Allendale Mill.
A final draft of the 3D model which I made to help work out the arrangement of buildings and the network of horizontal flues (highlighted in green)
The equipment for washing the iron ore of unwanted material were called 'Brunton Buddles'. I made a 3D model of these to try and understand how they functioned. Material was loaded through a hopper at the top and then passed on to a canvas belt where water washed away the unwanted material leaving lead-rich ore to drop into a large tank for collection.