Swan View Tunnel is an old railway tunnel east of Perth, in the John Forrest National Park. Since its closure, it has become a popular hiking/Instagram destination. It’s a challenging candidate for 3D recording, due to it’s large size and unlit interior – but as the first rail tunnel is Western Australia it is considered a heritage site of high significance. On a clear Saturday afternoon, I spent 2 hours recording the entire tunnel, end to end.
With my camera on manual and the settings dialled in to correctly expose the inside of the tunnel, I started the main recording. I walked down the center one step at a time, shooting directly down the tunnel at head height. The flash was on from the moment I entered the tunnel, which gave more than enough light to light up the several metres in front of me. Camera details for the inside of the tunnel are listed below.
|Lens||Sony 16-50mm, set to 16mm (24mm full frame eqiv.)|
|Focus||Manual – set to 6m.|
|Resolution||24mp JPEG – Fine detail|
The greatest challenge of the day was unexpected – waiting for the flash to cool down. After 5 or 6 shots in quick succession, the camera would force a wait time of about 20 seconds between flashes, which added up fast. Most of my time was spent waiting. Hikers and bikers were also a challenge; their impact on the model would likely have been small, but once people get close it’s obviously uncomfortable to keep photographing them (especially with a blinding flash).
The next step was to record the entrances, which simply required an adjustment of exposure to preference detail in the shadows without rendering the daylight parts unrecoverable. The ends turned out a bit ugly, I’d recommend spending more time than I did.
The final step was to record the recesses in the side of the tunnel. I took 5 to six photos looking towards each
Processing took the rest of the afternoon. I used
|Align Photos||Medium, Generic Preselection||45 mins|
|Dense Cloud||Low, Mild Depth Filtering||2 hours, 40 mins|
|Build Mesh – Full||High (7,365,748 faces)||49 minutes|
|Decimate Mesh – Web||Custom (200,000 faces)||5 mins|
|Build Texture – Full||4096px by 4. Hole/Ghost on.||50 minutes|
|Build Texture – Web||4096px by 2. Hole/Ghost on.||35 minutes|
I was also able to bring the model into Blender for some relighting and editing. The image below is a simple Cycles render of the web version, with some added lighting for mood. The composite image at the top was also partly made with Blender. I used the decimate modifier, a custom wireframe style and OpenGL Render to render out a black and white image from the perspective of that camera, then I added the exported normals map from Photoscan for it and composited them together in Photoshop.
I’m genuinely surprised this worked, it’s the largest model I’ve recorded so far, with especially difficult lighting conditions. Redoing this I would maintain my strategy of taking photos just one way up the tunnel, with special clusters to resolve complex features. I would investigate using a more robust flash – which would more than half the time required.