The se­crets be­hind 3d scan­ning

Pro­fes­sional 3D scan­ning com­pany, Pixel Light Ef­fects, re­veals its pho­togram­me­try process for get­ting ac­tors into the dig­i­tal realm

3D World - - CONTENTS -

Pro­fes­sional 3D scan­ning com­pany, Pixel Light Ef­fects, re­veals its pho­togram­me­try process for get­ting ac­tors into the dig­i­tal realm

When­ever you see a comic-book hero fly­ing through space or crash­ing through a wall, chances are they’re a dig­i­tal dou­ble of a real ac­tor ex­pertly crafted by a vis­ual ef­fects stu­dio.

But how is an ac­tor’s like­ness cap­tured with such ab­so­lute pho­to­re­al­ism? These days that’s of­ten the do­main of 3D scan­ning providers, which rely on por­ta­ble – and of­ten cus­tom – pho­togram­me­try rigs that they can bring right onto the set. That way they can whisk ac­tors in and out of the scan­ning process and gen­er­ate a CG model of their face and body as fast as pos­si­ble, help­ing save the film stu­dio a lot of ex­pen­sive pro­duc­tion time.

One com­pany in the 3D scan­ning ser­vices fold is Vancouver-based Pixel Light Ef­fects. Us­ing its mo­bile pho­togram­me­try setup, the stu­dio re­cently scanned prin­ci­pal ac­tors and ex­tras on lo­ca­tion in Bri­tish Columbia for Matt Reeves’ War

for the Planet of the Apes, cre­at­ing de­tailed CG mod­els to give to Weta Dig­i­tal for the sub­se­quent dig­i­tal dou­ble work.

3D World asked Pixel Light Ef­fects, which also has a pres­ence in Bei­jing, how it tack­les a typ­i­cal ac­tor pho­togram­me­try scan – from the cap­ture process right through to pro­duc­ing a use­able high­res­o­lu­tion CG model.

The ba­sis of a 3D ac­tor scan

Over the years, sev­eral meth­ods have been used to ac­cu­rately cap­ture the essence of an ac­tor in CG. These in­clude laser scans, spe­cialised ‘light stage’ con­trap­tions, and now most com­monly, pho­togram­me­try. This process essen­tially in­volves tak­ing hun­dreds of pho­to­graphs of the ac­tor from mul­ti­ple an­gles. The pho­tos are fed into com­puter soft­ware, which then sets about com­par­ing the im­ages and us­ing them to build a 3D model.

Pho­togram­me­try is con­sid­ered an ef­fi­cient method of cap­ture be­cause it is quick, es­pe­cially in a cam­era rig that has many cam­eras at many an­gles tak­ing all the

pic­tures at the same time. In­deed, that’s what Pixel Light Ef­fects uses, and fur­ther mo­bilises the scan by hav­ing it take place in the back of a truck that has the pho­togram­me­try rig per­ma­nently in­stalled in­side. The truck can be driven di­rectly to the set where the ac­tors are, or just about any other lo­ca­tion.

“Mo­bil­ity is the big­gest is­sue with a rig con­sist­ing of hun­dreds of cam­eras,” says Pixel Light Ef­fects’ CEO, Jingyi Zhang. “Tak­ing them apart and putting them back to­gether is very time-con­sum­ing and labour in­ten­sive. It just doesn’t feel right. How­ever, due to the tight sched­ule of the pro­duc­tion, some­times it’s just im­pos­si­ble to have the tal­ent come to us. Be­ing able to per­form the ser­vice on set is very es­sen­tial.”

What’s in the truck?

Pixel Light Ef­fects’ pho­togram­me­try rig, contained in a mod­i­fied Mercedes-benz Sprinter van, is made up of 144 Canon DSLR cam­eras. These are all syn­chro­nised us­ing a pro­pri­etary ‘Cam­era Hub’ de­vice, which sup­plies power and trig­gers 16 cam­eras at once. “It’s de­signed to be daisy-chained to­gether, so we use mul­ti­ple de­vices to trig­ger the larger ar­ray,” ex­plains Zhang.

Light­ing is an es­sen­tial part of the pho­togram­me­try rig. For this, mul­ti­ple flashes and bounce light en­sure that there is enough depth of field in the re­sult­ing im­ages, and that the ac­tor is lit evenly. The van in­te­rior is also decked out

“Ev­ery­one who does pho­togram­me­try knows you just can’t have Enough cam­eras” Jingyi Zhang, CEO, Pixel Light Ef­fects

in white and the en­vi­ron­ment is cal­i­brated so that it is as dif­fuse as is pos­si­ble.

The cam­era po­si­tions in­side the rig were R&D’D by Pixel Light Ef­fects for sev­eral months before an op­ti­mal lay­out was reached. “Ev­ery­one who does pho­togram­me­try knows you just can’t have enough cam­eras,” notes Zhang. “You al­ways want more. Hav­ing a con­strained bud­get and space means we must have just enough cov­er­age at every an­gle.”

In­side a scan­ning ses­sion

When an ac­tor comes into the truck for a scan, Pixel Light Ef­fects typ­i­cally has just two tech­ni­cians run­ning the scan­ning ses­sion. First they will ask the ac­tor and on-set su­per­vi­sors if it is okay for the tal­ent to wear a hair net. “This gives a more ac­cu­rate skull shape, which will be help­ful down in the pipe­line,” ex­plains Zhang. How­ever, it may be cru­cial for an ac­tor to re­tain their ex­act wardrobe, such as a hel­met or a faux hair­piece.

For a full-body scan (Pixel Light Ef­fects also car­ries out de­tailed fa­cial scans – see Face­time box­out), the ac­tor will be in­structed to make an A-pose, with their el­bows and knees slightly bent for rig­ging pur­poses. The ac­tor’s face is typ­i­cally posed in a neu­tral way and then aligned with ex­tra wit­ness cam­eras.

The ac­tual cap­ture is like tak­ing a photo, again high­light­ing the ben­e­fits of a pho­togram­me­try rig. “The cap­ture it­self is as fast as tak­ing a photo at 1/1000th of a sec­ond,” says Zhang. “All the cam­eras are syn­chro­nised, which means we can scan an­i­mals – who of course don’t stay still – as long as they fit in the cap­ture vol­ume.”

Scan and de­liver

The re­sult­ing pho­to­graphs are sim­ply raw im­ages, but they are

“the cap­ture is as fast as tak­ing a photo” Jingyi Zhang, Pixel Light Ef­fects

The pho­togram­me­try cam­era ar­ray in­side the Pixel Light Ef­fects van is made up of 144 Canon DSLR cam­eras.

Pixel Light Ef­fects uses both Agisoft Pho­to­scan and Real­i­ty­cap­ture, seen here, to re­solve mod­els from its pho­togram­me­try cap­ture process.

Raw pho­to­graphs of sub­ject Sam Yunussov, pos­ing as a Rus­sian para­mil­i­tary mem­ber, from one of the 144 cam­eras taken dur­ing the pho­togram­me­try scan.

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