TITLE: The Forth Railway Bridge
NAME: David Wilkinson
COUNTRY: Scotland
EMAIL: davidwilkinson@cwcom.net
WEBPAGE: hamiltonite.mcmail.com
TOPIC: Landmarks
COPYRIGHT: I SUBMIT TO THE STANDARD RAYTRACING COMPETITION COPYRIGHT.
JPGFILE: forthbri.jpg
ZIPFILE: forthbri.zip
RENDERER USED: 
    POV-Ray 3.1g

TOOLS USED: 
    PSP for converting tga to jpg

RENDER TIME: 
    parse time 36 seconds; total rendering time 48 minutes 6 seconds.

HARDWARE USED: 
    PII 350 - 64Mb

IMAGE DESCRIPTION: 
    The railway bridge over the river Forth in Scotland is a
landmark in many senses of the word.  Built in 1890 it was the first large
structure built entirely of steel.  It dominates the landscape now, just as it
did when it was first built.  Its design in 1881 by John Fowler and Benjamin
Baker was a tour de force of its age and, following the Tay Bridge disaster of
1879, was a courageously bold statement of engineering endeavour.  The bridge's
full length is 1.2 miles, it took 7 years to build and cost the lives of 57
men.  It was fabricated on site from 51,000 tons of steel plates and steel
sections using over 7 million rivets.
The image shows a view from upstream of Queensferry.  I have shown a 1930's
steam locomotive on the bridge and although this is to scale and is fully
detailed, the size of the bridge's structure is such that the locomotive
appears insignificant.  From being built, the bridge was painted with red lead
paint and it remains that way today - a patchwork of rust and red paintwork.
   

DESCRIPTION OF HOW THIS IMAGE WAS CREATED: 

The bridge is defined to a scale of 1 POV unit = 1 foot.  It is all hand coded
(using POV's built-in editor) of standard CSG elements - boxes, cylinders,
cones and prisms.
Initially I had a struggle getting dimensional information on the bridge.  There
is a web site, but this was not very helpful for my purposes.  My first
breakthrough was locating a book on Amazon(John Fowler, Benjamin Baker, Forth
Bridge; Axel Menges 1997).  This book contains a selection of magnificent
photographs, and, more importantly for me, reproductions of some scale drawings
of the bridge.  This arrived on 30 July and my work on the bridge started from
that date.  A response to an email to the originator of the web site gave me
another lead.  The centenary of the bridge in 1980 was celebrated with a
re-issue of the book by Wilhelm Westhofen published by Engineering magazine in
1880 - and this was freely available for borrowing through my local library! 
This wonderful source document is a detailed account of the design and
construction of the bridge with many scale drawings and contemporary
photographs.
Unfortunately, the possession of source drawings still leaves a lot of
dimensional information to be scaled, calculated, or just guessed.  I now have
dozens of sketches and calculation on pieces of paper, and, on looking back at
those I made just a couple of weeks ago, they are as unfamiliar as my school
notebooks of many years ago.
The image, is, of course, unfinished.  There is the question of the shorelines
for instance - obscured by a convenient sea mist in my image  :-) and there are
many more girders to be painstakingly added.  The stone piers have given me
some problems.  I used the brick pattern with granite textures, and on the
sloping walls of the pier this gave rise to hideous artifacts (courses of
mortar where there should be bricks).  After some experimentation I managed to
minimise this by rotating the texture to 10 degrees greater than the slope of
the walls.
In spite of these imperfections and missing details, I think the image gives a
pretty good idea of the power of the structure.  I hope you like it.
Image Statistics;
69,047 objects;  memory used 65,691,942 bytes;
Antialias=On; Sampling_Method=2; Antialias_Depth=2; Antialias_Threshold=0.1;
Radiosity=1
(The zip file contains the macro for the lattice girder used extensively in the
bridge and the source for the Pier seen in the image.)

