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Chang Qiao

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The ChangQiao Bridge is a sculpture in the Yedo_Basilica sculpture gardens by Lillie Yifu. SURL.

It was created in December 2007.

Historical Information

Late antiquity on the Eurasian continent is an under studied period in the West, and in China it is a period whose existence is generally denied in order to underline the long imperial continuity. These are both mistakes.

On the Eurasian continent, antiquity ended with a thump, and the coming of a series of migrations which tore at the fabric of the old centers of empire. In Europe this was seen as the "migration period," or barbarian invasions (100 – 500 CE) but it must also include the rise of Islam (622 – 732 CE), and the collapse of the Han dynasty through the era of disunity (200 CE – 589 CE). But during this time immense technological innovations were put into use, only to be swamped by the pressures of what was to be a chaotic age.

China as the cradle of the blast furnace

In China late antiquity evolved a process to manufacture iron and steel in larger quantities than before, or anywhere else in the world. In China the blast furnace dates from 500 BCE, almost two thousand years before its introduction into the west. A blast furnace introduces ore at the top, and oxygen at the bottom, with the air rushing upwards and the ore falling downwards. This leads to chemical reactions taking place over the entire length of the furnace. The earlier technique, the bloomery, produced a result with blooms of usable, low carbon, iron, where as the full blast furnace produces a high carbon iron called "pig iron" which is uniform. The next challenge is to reduce the carbon content of this brittle metal to make it workable, or to produce steel. This is done by allowing molten pig iron to "puddle," reducing it's carbon content, and then mixing pig iron in with the de-carbonized iron to produce steel, an alloy of iron with a small percentage of carbon.

Iron in Chinese Bridge Building

China used iron chain bridges by 600 CE, and soon afterwards built the celebrated ZhaoZhou bridge ( ) which uses iron reinforcement, and is the first bridge known to have used "open spandrels," or spaces between the arches, to reduce weight and material. It was spans the Xiao River, and was completed around 605 CE.

The Chang Qiao Bridge

This piece is entitled Chang Qiao, for "Lady in the Moon Bridge." Chang is the name given to the beautiful woman in the moon in China.

Use of Huge Prims

In Second Life terms this bridge uses huge prims, primitives larger than can be created by standard editing, and an illusion to create a reflection effect. There is no pure reflective surface in Second Life exactly, instead, in the many builds where a shiny reflective surface effect is desired, the standard method is to make a copy of the original, flip it upside down, and make the surface between them semi-transparent. Our eyes learn as children to interpret seeing this as a reflection, and not an object "beyond" the mirror, though in this case that is exactly what happens. Here the surface is the water, which creates the shimmering effect.

It is possible by shifting the camera angle to points below the ground to see the full shape of the bridge that produces this illusion.

Meaning of the Name

The shape of the bridge is a reference to the Chinese character for the Moon, ( ). In China the traditional bridge shape is called the half moon.

Use of a rezzing alignment script

The other important technique shown here is the use of a script to align primitives. While primitives can be aligned by hand, the results for curves and arcs are too imprecise. Instead, the walk way sections of the bridge were built by each section rezzing the next, and aligning it to the center of the circular shape of the bridge.


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