Thursday, 3 April 2014

A Word or Two From Phil About Belah

Phil Baines talks us through the process of building the incredible structure that is Belah Viaduct:

The Building of Belah Viaduct - Part 1

Sir Thomas Bouch was a famous railway engineer particularly noted for his lightweight bridge designs, unfortunately he is mainly remembered for the infamous Tay bridge disaster. However, Belah Viaduct is another of his designs and is considered an iconic structure of the Stainmore route, hence was an obvious choice to be built in the early development stages of this new route for TS2014.
The first problem with building a model of the viaduct is that it no longer exists, torn down for scrap in 1963 all that remains are the two abutments, only accessible across muddy fields and with the farmers permission.

Fortunately there are a number of photographs available and Peter Waltons excellent book, "The Stainmore and Eden Valley Railway", contains a number of drawings detailing  the structure.
The viaduct was 347 yards long, 24 feet wide, with 16 spans, and at 196 feet, it was the highest bridge in England when it was built. Consequently it was going to be a large model and some discussion was held between team members about how detailed to make the model. It was estimated a 3D model would run about  150,000 polys, which could be radically reduced by using transparent 2D textures for some elements, such as the handrails. After discussion it was decided that, as such an important element of the route, it should be highly detailed, particularly as the area around the site was open country with very few other assets and, even at 150,000 polys, it would be less than the consist on top of it!
So work began and the starting point was the handrail. These were very attractive cast iron rails as seen in this drawing from Peter Walton's book.

These railings appear on three of the viaducts on the Stainmore route, Belah, Deepdale and Tees Viaduct, so it made obvious sense to create a lofted version of the handrail so it could be easily added to all three bridges. Also. the repetitive nature of the design lends itself to a lofted model.
There were a number of potential methods for creating the handrail model, extruded splines for instance, but the simple geometric design made me choose the following method.
 I started with a simple box which, always remembering to build it 0.36 meters below ground level as the loft it populates will be at railhead height, which is that distance above ground level. I then subdivided the box into the geometric pattern.

Next, I selected the relevant polys and beveled them inwards.

Then it was a simple matter to punch through the highlighted polys and with a little manipulation of the top section to create the wooden handrail and with the addition of a supporting I-beam, I had a section of handrail ready for unwrapping, texturing and shadow baking.

Three  jobs left to do.
Firstly, when I make a lofted item like this I like to extrude and taper one end so that one piece fits inside the other to avoid nasty gaps showing when the loft bends. You can just make these out in the above picture, they are the dark pieces at the right-hand end of the model.
Secondly, I need an end geometry for the loft. This was achieved by extruding the wooden handrail part of the model then using the bend modifier.

Finally, off to the blueprint editor and create an invisible LoftSectionBleprint which is populated with my handrail model as middle geometry and the end geometry as above, then try it in game.

Success! be continued.

Next, Phil will show us how he created the viaduct supports

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