大片扫描：使用LIDAR为Joker和John Wick

作者：约翰·阿什比

John Ashby is LiDAR supervisor at光环外汇, a company providing on-set data acquisition services for the film and gaming industries. Ashby has worked on Hollywood blockbusters includingJokerandJohn Wick: Chapter 3 – Parabellum, capturing 3D scans of film sets and locations. The captured scan data are used in many ways during film production, especially for creating VFX (visual effects).

随着时间压力，这项工作的主要挑战之一，阿什比使用Leica ScanStation P50long-range 3D laser scanner for high-resolution, fast scanning. And with lots of data to juggle, he usesLeica Cyclonesoftware for easy processing of large numbers of scans.

The benefits of reality capture in the film industry

Using LiDAR and other laser scanning technologies is helping the film industry to increase efficiency in production and post-production, and at the same time, create more realistic visual effects. A scan of a film set or location provides an accurate record. which can be used to help match camera angles. This ensures continuity and sets the foundation on which to build any virtual assets, for example, a digital set extension.

Using LiDAR to improve the realism of VFX

Having a scan as a reference point helps VFX teams create more seamless effects. Previously, footage of a film set would be used to make a virtual recreation in 3D. To add realistic-looking effects, the technicians would need to match the same camera angle and motion as in the original shot (‘match moving’). Without laser scanning crews would take detailed measurements but couldn’t achieve 100% accuracy. By capturing the entire 3D world of any shot, LiDAR and laser scanning combined offer a precise map from which to work.

Ashby gives an example from his work on小丑。“I scanned a lot of sets, including Arthur’s apartment, and the TV set for the Murray Franklin talk show, which I scanned because there was all this CG blood that had to get added in post and this allowed them to get a perfect camera track of those sets.”

快速扫描速度要求uired for scanning in a frantic environment

速度对于设置扫描至关重要；凭借大型船员和巨大的运行成本，数据收集不会延迟电影制作。：“这全是关于您在最快的时间内可以得到的最多数据，而无需支撑生产，” Ashby解释说。

When working onJohn Wick 3: The Continental,Ashby had only four hours to scan and photograph a major location. “The building for the shoot-up of the Continental was One Hanson Place in Brooklyn which is huge. It was just a pure race against time.” Ashby needs to get as much data as possible and to be prepared to stop and start scanning to fit around filming, sometimes even grabbing scans between shots.

Ashby explains his process of LiDAR scanning on set or location, “I tend to start with a quick blitz of the particular environment to get a ‘registration’ of it. This is just lots of fast low-resolution scans; it’s just so I know in the worst-case scenario, I’ve got a full registration of the environment. Then I’ll go around and do my luxury scans from different ‘stations’...upping the resolution and sampling quality in order to get the more distant and reflective surfaces.” This is where Ashby uses the ScanStation P50, which he finds twice as fast as the other laser scanners he uses for shorter range work.

Ashby解释说：“我拥有Leica Geosystems扫描仪设置的方式是，在10米处的分辨率为每0.6厘米1分……您正在捕获更多的数据，” Ashby解释说。“扫描仪P50的数据令人难以置信地干净 - 非常快。”

Using LiDAR scanning to improve continuity

通过创建拍摄环境的虚拟3D版本，LiDAR扫描使您可以更轻松地从不同角度看到对象的位置，并确保事物在应该的位置。Ashby解释说：“ LIDAR真正帮助您做的是，当您从不同的相机角度进行多次拍摄时，您可以跟踪LiDAR数据的所有内容，并将所有相机捕捉到同一世界空间。”“这意味着，如果您将某些东西一次放在3D空间中，它将在所有其他镜头中在相同的3D空间中。”

Using an example of a scene from小丑，Ashby talks about a scene with a lot of cuts. The scan helped the technicians to match CG blood from different angles, “What it means is that the blood in shot A lines up perfectly with the blood in shot B.”

Easy-to-use software is essential for checking high numbers of scans

The need to stop and start scanning can complicate the process of registering scans together. “All your scans can get really jumbled around. So a good logging system is key and then it’s much easier when you have to manually align your scans after,” clarifies Ashby.

Ashby uses Cyclone software for post-processing and likes the amount of control that it allows for manual alignment. “The Cyclone software package is very fast for that. You just overlay them [scans] on top, you quickly just line them up and that’s pretty much it…You can get through about 80 scans in about a couple of hours.”

In other industries like construction or manufacturing, a scan would be used to create a highly detailed 3D model of the environment, however, in the film industry an OBJ (polygonal mesh) is often the preferred output, containing all the detail that’s required; “OBJs are pretty unbreakable as a format and generally the most requested deliverable.”

Ashby’s job is then complete as he delivers the scans to others working on the production, “I typically hand off everything to production or a visual effects studio.” Having packed his laser scanners into flight cases, the LiDAR supervisor is ready to head off and use his Leica Geosystems laser scanner on the next set.

基于：激光扫描为小丑和约翰·威克（John Wick）