Transforming Chinese temple archway into a magnificent 3D model with Artec scanning technology

Challenge: To 3D scan a large, ornately carved archway in a tight space

Solution: Artec Eva, Artec Space Spider, Artec Studio

Results: A highly-detailed, watertight 3D model of an architectural landmark at a sacred Buddhist site was created using a combination of handheld 3D scanners

“Playing with pearls, two dragons will be soaring high in the sky.” That’s how the prodigious Chinese artist and stonemason Hu Mingzhu envisioned the scene to crown an architectural masterpiece that would immortalize his name across the sacred region of Mount Wutai, northern China. 100 years later, his ornate dragon-themed archway, embellished with exquisite, multi-layer carvings of fruit, flowers, and both mythical and real-world animals is back in the realm of the intangible, recreated as a 3D model in its finest detail in the framework of a conservation project.

The archway in front of Longquan Temple on Mount Wutai

Acknowledged as a World Heritage Site by UNESCO and an AAAAA (top-tier) tourist attraction by the Chinese National Tourism Administration, Mount Wutai, or the Five Terrace Mountain, is the first of China’s Four Sacred Mountains of Buddhism. Mount Wutai has been a place of homage for millions of pilgrims from across the country since as early as the 1st century CE, when monasteries started to be built on its five flat peaks.

The first ever 3D model of the Longquan Temple archway in geometry-only mode

Today, Mount Wutai is home to more than 40 temples, among which Longquan Temple is distinct for its unique architectural style that the legendary Hu Mingzhu (1895-1968) contributed to.

Hu Mingzhu’s rise to fame

A son of a school teacher, Hu Mingzhu started working as an apprentice at a carpentry shop on Mount Wutai when he was 10 years old. In addition to masonry, he took great interest in calligraphy and painting. Touted as diligent and persevering, yet daring and free-spirited, young Hu Mingzhu was admired by both his teachers and peers. “The disciple has surpassed his master,” his mentor Liu Yuancheng once said about him.

However, it wasn’t until his mid-20s that Hu Mingzhu was trusted with his first major project. At the time, Longquan Temple had lined up a bid to design and build a sanctuary for the late monk Puji. Hu Mingzhu drew up and presented his project, among other contestants. This one topped the competition alongside one pitched by a group of artisans from the neighboring Hebei Province. Lamentably, following an interview with the abbot of the monastery, Hu Mingzhu was turned down due to being too young and inexperienced.

The Hebei team embarked on construction but, when it was well underway, requirements were toughened, especially with regards to the carving that the walls of the sanctuary were to be adorned with. Falling short of skilled masons to complete the project, the Hebei team just abandoned it only halfway through. The abbot of the monastery had to turn to Hu Mingzhu, who didn’t take long to round up talented assistants from far and wide, refine the initial sketches, and distribute tasks among his men so as to see the project through in the speediest manner. When the sanctuary was unveiled, everyone marveled at the beauty of the stonework featuring gurgling waters of a mountain stream.

Creating the masterpiece archway

A year later, Hu Mingzhou won his next bid, one to erect a carved archway in front of Longquan Temple, in order to magnify the glory and significance of the latter. The artist first shaped his vision of the archway design in a miniature prototype made of yellow wax. Combining the best of the two worlds, Hu Mingzhou interlaced China’s traditional woodwork patterns with his own stone carving techniques. “A gem of gems!” one member of the review panel exclaimed while gazing upon the prototype.

Ornate carving above the main gate of the archway

A total of 50 craftsmen toiled doggedly under Hu Mingzhou’s supervision six years straight, and in the fall of 1930 the archway was finished. This architectural wonder rests atop a staircase made up of 108 steps – a sacred number in Buddhism. Its three gates are formed by four square-shaped piers supported by four columns on the front and four on the back. All sides of the pillars feature artistic representations of dragons. The vaults of the gates are remarkable for their meticulously carved blossoming peonies, ripe persimmons, traditional Chinese writing brushes, paper fans, treasured books, etc. As well, more than 20 stone-carved lions in different postures are to be found in the middle of the archway. Its centerpiece comprises depictions of scenes from the life of the Buddha, above which one can see a lotus-petal-shaped vertical plaque with words of wisdom engraved on it, “Buddha’s light shines through.”

A figure of a lion poised for attack

Scanning challenge taken

All this bustling variety of elaborate shapes needed to be reconstructed in digital form in order to preserve this cultural treasure for posterity.

Two requirements were set:

  • First, each element of the archway was to be rendered in 3D with utmost accuracy. No gaps in the final 3D model would have been acceptable.
  • Second, it was requested that it should be possible to break down the master 3D model into the structural parts the archway consists of, so each of them could be examined separately.

There was no better way to meet both criteria than by employing 3D scanning technology. With a handheld 3D scanner, you can move around the object, capturing its surface section by section, from all necessary angles.

Portable 3D scanning is what the team of Artec 3D’s Gold Partner Beijing Onrol Technology Co., Ltd. is truly proficient in. The company was contracted for the archway scanning project that promised to be quite challenging. They decided to go with a combination of two handheld 3D scanners: Artec Eva and Artec Space Spider.

Artec Eva features a larger field of view and a higher scanning speed than Space Spider, and therefore can capture a given surface area faster. The strength of Space Spider is a higher 3D point accuracy (up to 0.05 mm) and a higher 3D resolution (up to 0.1 mm). So Eva was chosen to perform an overall scan of the archway, while Space Spider would digitize its most intricate details.

A close-up view of the front part of the 3D model

Before the job could be started, it was necessary to ensure the entire structure could actually be 3D scanned from top to bottom. The space around the archway is very confined, with not enough room for the use of standard scaffolding equipment to reach its upper parts. Nevertheless, the team devised a secure set of ladders to access areas that couldn’t have been scanned from the ground, in particular the eaves, which needed to be captured from above.

Another factor to consider was the sunlight: at an altitude of 3,000 meters, it appears to be brighter than at normal altitudes and is reflected more intensely, especially from smooth, polished surfaces, which the archway is abundant in. This could have prevented either scanner from capturing the geometry and texture of the object correctly. Both Eva and Space Spider stream the 3D data they collect to Artec Studio software, which reconstructs the shape of the object by analyzing every minor distortion in the rays of structured light the scanners emit after the light reaches the object surface and bounces back to the scanners. Normally, you can use shading to avoid overexposure, but in this case, given how confined the space was, this option was left out. On cloudless days, some of the scanning had to be done after sunset.

Capturing parts of the archway with Artec Eva 3D scanners at night

The scanning was completed in 14 working days, with about 500 GB of raw data collected – that roughly equals 100,000 photos taken with a good smartphone. Scans from both Eva and Space Spider are compatible with each other and can be easily fused in Artec Studio. Every release of the software sees enhancements which expedite data processing and offer new tools for editing scans the most convenient way.

The brilliant results

A month later, the project was finished, and the quality of the 3D model amazed the customer, just like the beauty of Hu Mingzhu’s original stonework had many monks and lamas of Mount Wutai’s temples spellbound when they first saw it.

The front view of the 3D model of the archway

The 3D model of the archway is preserved for generations to come and can be studied by architects, artists, and sinologists, even if they never make the journey to Mount Wutai itself. Likewise, the 3D model can be displayed in classrooms, serving as supplementary material for teachers of Chinese history. It’s especially valuable that the upper parts of the archway, normally eluding any close look, can now be viewed in high resolution. Thanks to 3D scanning technology, for the first time in history, every tiny corner of this landmark is clearly visible to anyone interested in it.