See­ing the city’s lava caves via dig­i­tal 3D modelling.

Tech­nol­ogy lets us see in­side the city’s sub­ter­ranean lava caves with­out ever set­ting foot in them.

Metro Magazine NZ - - Contents - TEXT — CHRIS BAR­TON

My first en­counter with Auck­land’s hid­den un­der­world be­gan at the bend of a cul-de-sac on the flanks of Te Tā­tua-a-Riuk­i­uta (also known as Three Kings). The walk up the long drive­way gave lit­tle away, other than to in­di­cate we were among the in­hab­i­tants of a gen­teel, leafy sub­urb.

We reached a plat­form that was clearly some­one’s deck. Now more or less sin­gle file, about 50 of us, some clutch­ing cush­ions, si­dled through an out­side shower cu­bi­cle and then down rough step-like rocks around a tree.

There, the ground fell away abruptly in a scree of rub­ble and boul­ders. De­scend­ing the rock­slide crab-like, my part­ner and I caused a traf­fic jam. No one wor­ried. The un­der­neath would wait.

At the base, the ground was still pre­car­i­ous, but flat­tish, the dark­ness re­lieved by strips of light­ing placed at the edges. Now more or less up­right, we picked our way along the cave floor to find a place be­side the side walls on which to perch. The in­sides dripped.

As we looked up through dark­ness in this strange and an­cient place with lit­tle dis­cernible form, there was enough light to see the roof of the cav­ern, cathe­dral-like.

Twenty-eight thou­sand years ago, molten lava had left this sub­lime build­ing, a sinewy, cooled-rock tube. This was Stew­art’s Lava Cave, the ar­chi­tec­ture of an ex­plo­sive nat­u­ral event, a sco­ria shel­ter per­haps in­hab­ited long ago. Caves like this are all over Auck­land’s vol­canic land­scape. Some have been burial cham­bers, oth­ers es­cape routes. One was once used as a mush­room farm, some more re­cently for par­ties, a book launch and now for a mu­sic recital.

Down be­low, ev­ery­thing above ceased to ex­ist, the sur­face a dis­tant me­mory. When com­poser Peter Hobbs played his syn­the­sis­ers and elec­tro-acous­tics, joined by Charmian Keay on vi­o­lin and Max­ine Cun­liffe on cello, the haunt­ing sound seeped into the rock, an­i­mat­ing the oth­er­ness of the be­neath.

Later, as we scram­bled up the rock­slide into the light, the be­low re­ceded into dark­ness and obliv­ion, ex­cept for the me­mory of the mys­tery, the mu­sic, the hol­low rock.

My sec­ond en­counter with Auck­land’s sur­real se­cret at the end of garages, un­der man­holes and in sub­ur­ban back­yards was in Septem­ber, in the cylin­ders of Silo 6 on Auck­land’s North Wharf, where the mu­sic of the ear­lier un­der­ground event was now the am­bi­ent score for Into the Un­der­world, an ex­hi­bi­tion by dig­i­tal artist Chi­rag Jin­dal.

Dig­i­tal artist. The prob­lem with the term is the tech­nol­ogy that makes the art, in this case a li­dar (light de­tec­tion and rang­ing) scan­ner. It was placed, with the help of spele­ol­o­gist Peter Cross­ley, in 11 of Auck­land’s lava caves, to blast pho­tons at the sur­round­ing sur­faces at 100,000 times a sec­ond. When each pho­ton bounces back, the ma­chine cal­cu­lates how far it trav­elled, cre­at­ing a vir­tual dot in 3D

space of wher­ever it strikes. As it tire­lessly re­peats the process, ro­tat­ing on a pivot and scan­ning ev­ery­thing around it in its line of sight, the li­dar cre­ates a 3D “point cloud” of the cave — in Stew­art’s cave, some 98,078,772 points — to cap­ture the 200m of multi-level pas­sages that com­prise the labyrinth. Soft­ware then ma­nip­u­lates the sci­en­tific data to cre­ate a 3D model, which Jin­dal cuts to show as either a ver­ti­cal or hor­i­zon­tal sec­tion.

The im­ages are ex­tra­or­di­nary and un­set­tling — largely black ex­cept for a fine fili­gree of bright white lines mark­ing the tex­ture and bounds of the cave, with hotspots of in­ten­sity in­di­cat­ing where the laser pulsed pho­tons, like a neg­a­tive image in the in­verse. You could ar­gue this isn’t art, but ar­chi­tec­tural rep­re­sen­ta­tion, the shape and form of the caves de­picted with ma­chine-like ac­cu­racy in a way never seen be­fore.

The ex­hi­bi­tion aims to make the hid­den ex­is­tence of the caves ir­refutable — to bring the se­crecy into the open, to re­cover what might be lost and to en­sure these nat­u­ral won­ders are pro­tected and val­ued. Some of these caves have been badly treated, in some cases as rub­bish dumps or filled with con­crete when dis­cov­ered on build­ing sites.

The caves, many be­low pri­vate prop­erty, some­times run­ning un­der sev­eral houses, raise mul­ti­ple ques­tions. Who owns what? How deep do prop­erty rights go? Do prop­erty own­ers own the ground to the cen­tre of the earth? Who went here be­fore?

The ex­hi­bi­tion’s an­swer to these vexed ques­tions of own­er­ship, preser­va­tion and stew­ard­ship is to make pre­cise, ex­act ar­chi­tec­tural draw­ings made of mil­lions of points rep­re­sent­ing spa­tial facts, ac­cu­rate to a mil­lime­tre.

What trans­forms these sci­en­tific im­ages into ar­chi­tec­tural art is the way the un­der­ground is com­bined with what lies above. En­ter the li­dar again, scan­ning the sur­face ter­rain to show the gar­dens, the houses, the cars and some­times the peo­ple of subur­bia above the caves. The two sets of scans to­gether vividly ex­press the sur­real ur­ban con­text, the past be­neath our feet. The above is dream­ily pho­to­graphic, ghostly, some­times cu­bist in the way a van might ap­pear su­per­im­posed twice and the out­line of dwellings is ex­plicit and hy­per-real. Adding to the dif­fer­ence be­tween worlds, some­times trees and veg­e­ta­tion are pho­to­shopped with sub­tle colour. Then there’s the thresh­old, some­times a hu­man in­ter­ven­tion — steps, a lad­der, a grotto, a vestibule — some­times a nat­u­ral rock­slide.

With all this tech­nol­ogy in play, vir­tual re­al­ity might have been ex­pected as the medium of dis­play. But while the ex­hi­bi­tion does have a pro­jected an­i­mated fly­through of a dig­i­tal 3D model of a cave, ev­ery­thing else is pre­sented old-school, in huge curved light­boxes in the man­ner of Louis Da­guerre’s dio­ra­mas. The re­sult is en­chant­ing, the back­lit panora­mas, par­tic­u­larly the sec­tional views, draw­ing the viewer into a mys­ti­cal, fan­tas­ti­cal land­scape. A world cre­ated from light and through light shone from be­hind. A world that in­vites dreams.

Over the cen­turies these caves have ex­isted, peo­ple have used them in a va­ri­ety of ways. But mostly they are pre­cious land­scapes that most Auck­lan­ders are un­likely ever to visit. The irony of these im­ages is that they in­vite just such a mag­i­cal pos­si­bil­ity.

ABOVE— A cave be­neath Shack­le­ton Rd, Three Kings, is re­vealed in a work by artist Chi­rag Jin­dal.

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