近期有朋友在后台留言询问关于ILM在Mocap上的解决办法，尤其是现在ILM在演员动捕服装上的设计，有朋友很好奇究竟演员身上穿的是什么？什么材质？为什么这么设计……刚好，HI VFX近期发现一篇非常详细的介绍，一起分享大家。 版权声明：本文著作权归原作者所有，奇番小编欢迎分享本文，您的收藏是对我们的信任，QFanW谢谢大家支持！
往期关于Mocapx相关知识推荐阅读：
1.动作捕捉(Mocap)的五种形式及各自优缺点分析
2.Mocap的电影拍摄使用/预算注意事项/具体技术选择
3.如何跟踪标记（Tracking Markers）最能协助视效工作
4.Motion Capture的简称叫什么；Encode Cam如何帮助导演和视效完成画面
5.什么是motion control，何时使用，需要哪些基本设备和注意事项
When most people think about the motion capture of actors, they are probably thinking about eitheroptical capture (where cameras pick up markers on a suit)orinertial capture systems (which make use of magnets, accelerometers and gyroscopes inside a suit).
当大多数人想到演员的动作捕捉时，他们可能会想到光学捕捉(摄像机捕捉衣服上的标记)或惯性捕捉系统(利用衣服内的磁铁、加速度计和陀螺仪)。
Butanother kind of capture, image-based capture (sometimes dubbed ‘faux cap’) is now also very common in helping to re-create on-set performances by utilizing suits with specific tracking markers on them and sometimes multiple witness cameras to help triangulate the performance in 3D space.A pioneer in this area was ILM, which launched its patented IMocap technology during the second Pirates of the Caribbean film, Dead Man’s Chest, in 2006.
但另一种捕捉，基于图像的捕捉(有时被称为“faux cap”)，现在也非常普遍，通过使用带有特定跟踪标记的套装，有时使用多个目击者相机，帮助在3D空间中三角测量性能，来帮助重现现场表演。这一领域的先驱是ILM，该公司在2006年加勒比海盗系列电影《加勒比海盗》第二部期间推出了IMocap专利技术。
On the first Pirates of the Caribbean movie, The Curse of the Black Pearl, ILM had, among several other effects challenges, realized a number of fully CG skeletal pirates, with a combination of optical motion capture and keyframe animation.Visual effects supervisor John Knoll, now chief creative officer at ILM, and animation supervisor, Hal Hickel, felt that something different was needed for the sequel, especially to realize the tentacled star Davy Jones.
在加勒比海盗系列电影的第一部《黑珍珠号的诅咒》中，ILM在众多特效挑战中，结合了光学运动捕捉和关键帧动画，实现了一系列完整的CG骨骼海盗。视觉效果总监John Knoll现在是ILM的首席创意官，动画总监Hal Hickel认为续集需要一些不同的东西，尤其是要实现触手可及的明星Davy Jones。
“The original inspiration for IMocap came out of a conversation that Hal Hickel and I had with director Gore Verbinski on the first Pirates of the Caribbean film,” relates Knoll. “Gore had told us that he intended Davy and crew to be all digital characters on the second film in the series.From the team’s experiences on Pirates 1, the manual matchamation done was time consuming and not particularly accurate. We had also had a failed attempt at doing optical mocap later to match, but Gore rejected it because we were essentially substituting a different performance into the shot.”
“IMocap最初的灵感来自我和Hal Hickel与导演Gore Verbinski在《加勒比海盗》第一部中的一次对话，”Knoll说Gore曾告诉我们，他打算让Davy和摄制组在这部系列电影的第二部中都扮演数码角色。从团队在《加勒比海盗1》中的经验来看，手动匹配非常耗时，而且并不特别准确。我们后来也尝试过用光学mocap来匹配，但失败了，但戈尔拒绝了，因为我们实际上是在用不同的性能来替代镜头。”
Since Davy and crew were always CG and didn’t have to make transitions like the pirates in the first film, Hal, recalls Knoll, thought ILM could put tracking marks on the performers to help get better matchamation.
据Knoll回忆，由于Davy和其他人都是CG，不需要像第一部电影中的海盗那样转换角色，Hal认为ILM可以在演员身上加上跟踪标记，帮助他们更好地适应环境。
“I remembered seeing a demo from ILM’s R&D department on how they did a two-camera mocap solve on Pearl Harbor for tiny digital stuntmen tumbling off the deck of a sinking battleship,” says Knoll. “That got me thinking about a similar witness camera approach, where we suit a performer with tracking marks of some kind, and shoot the performance with witness cameras to triangulate positions.”
Knoll说:“我记得看到ILM研发部门的一个演示，演示了他们如何在珍珠港电影里为一艘正在下沉的战舰的甲板上翻滚的小型数码特技演员制作双摄像头动作捕捉解决方案。”“这让我想到了一种类似的目击者摄像机方法，我们让一名表演者带上某种跟踪标记，用目击者摄像机拍摄表演，以三角定位。”
A meeting was set up with ILM’s R&D group to lay out the challenge for some kind of on-set system that could help with matchamation. “The goal,” notes Knoll, “was to get close to optical motion capture quality, but with a small footprint on set, and able to handle difficult location shooting conditions.”
与ILM的研发团队召开了一个会议，讨论如何开发一种能够帮助匹配现场系统。“这是我们的目标，”Knoll说，“是接近光学运动捕捉的质量，但在设置一个小的足迹，并能够处理困难的位置拍摄条件。”
The stipulation was that there would be no constraints on cameras or lighting (visual effects artists will know that there has traditionally been a stigma associated with VFX taking up precious time on set). “We wanted to come up with a performance capture system that had an extremely small on-set footprint and was portable, since we knew that the upcoming films would involve complicated sets and a great deal of location work,” adds Knoll.
规定是不限制相机或灯光(视觉效果艺术家将知道，在传统上，视效问题占用了宝贵的片场时间)。Knoll补充说:“我们想要设计一种性能捕捉系统，它在片场占用的空间非常小，而且便于携带，因为我们知道即将上映的电影将涉及复杂的场景和大量的外景工作。”
It’s important to note that IMocap is not just about the suit. The system is heavily based in extracting data from the plate and witness cameras.“The original concept was to use ILM’s Academy Award-winning tracking and matchmoving software, M.A.R.S., to see if we could solve the motion of a skeleton,” explains Knoll. “We could already track and solve rigid objects with M.A.R.S. and the idea was to attach rigid, three-dimensional objects of known size and shape to the performer for tracking, and translate their motion into the motion of a simple, mocap-style skeleton. These objects are what became the “ILM IMocap Bands.”
需要注意的是，IMocap不仅仅是关于服装的。该系统主要基于从素材和目击者相机中提取数据。最初的想法是使用ILM获得奥斯卡奖的跟踪和匹配移动软件M.A.R.S.，看看我们是否能解决骨骼的运动，”Knoll解释说。“我们已经可以用M.A.R.S.追踪和解决刚性物体，我们的想法是将已知大小和形状的刚性三维物体附加到表演者身上，让他们进行追踪，并将他们的运动转化为一个简单的、mocap风格的骨架运动。”这些物体就是后来的“ILM IMocap条带附属物”。
Indeed,the original architect of IMocap was ILM R&D supervisor Steve Sullivan (who, along with engineers Kevin Wooley, Brett Allen and Colin Davidson, received a Scientific & Engineering Technical Achievement Academy Award in 2010 for IMocap).
事实上，IMocap最初的架构师是ILM研发主管Steve Sullivan(他与工程师Kevin Wooley、Brett Allen和Colin Davidson一起，于2010年因IMocap获得了科学与工程技术成就奖)。
“Steve has a PhD in computer vision and was the original author of the first version of ILM’s M.A.R.S. tracking system, for which he also won an AMPAS Technical Achievement Award in 2001,” says Knoll. “Colin Davidson was one of the main developers of IMocap. Colin, who also has a PhD in computer vision was responsible for the core solver that was used on Pirates 2. Brett Allen, another computer vision PhD, was also one of the core engineers in the development after Pirates 2, and also developed ILM’s ‘IMocaptain’ tool. Kevin Wooley was one of the system’s champions from the beginning. As a general motion capture expert, he was IMocap’s main ‘power user’ and was instrumental in the design of the overall system, including the design of the bands.”
Knoll说:“Steve拥有计算机视觉博士学位，是ILM的M.A.R.S.跟踪系统第一版的原作者，他还因此在2001年获得了AMPAS技术成就奖。”Colin Davidson是IMocap的主要开发者之一。拥有计算机视觉博士学位的科林负责《加勒比海盗2》的核心解决方案。Brett Allen是另一位计算机视觉博士，也是《加勒比海盗2》之后开发的核心工程师之一，他还开发了ILM的“IMocaptain”工具。Kevin Wooley从一开始就是这个系统的拥护者之一。作为一名普通的动作捕捉专家，他是IMocap的主要‘高级用户’，并在整个系统的设计中发挥了重要作用，包括带子的设计。”
Mike Sanders was also a key person involved in the development of IMocap, leading the hardware/prototype/production side of things, and in particular the design of the suits and bands. He would also go on to supervise several IMocap productions at ILM.
Mike Sanders也是IMocap开发的关键人物，他负责硬件/原型/生产方面的工作，特别是服装和腕带的设计。他还将继续在ILM监督几部IMocap的制作。
Now, back to the IMocap Bands.The R&D team at ILM realized that, by using rigid objects of known size and pattern that could be modeled in software, it wasn’t necessary for each ‘marker’ to be visible from multiple camera views. This is, of course, where IMocap differs from most optical mocap systems.
现在，回到IMocap带子上。ILM的研发团队意识到，通过使用可以在软件中建模的已知尺寸和模式的刚性物体，没有必要让每个“标记”从多个视角的摄像机视图中可见。当然，这就是IMocap与大多数光学mocap系统的不同之处。
“Unlike tracking markers with an optical mocap system,” states Knoll, “which requires a marker to be visible from multiple cameras in order to triangulate its position,if enough points around a band are visible, even from only a single view, we can solve its position and orientation in 3D space.”
“不像光学mocap系统跟踪标记，”Knoll说，“它需要一个标记从多个摄像机可见，再以三角定位其位置。现在我们可以做到如果一个波段周围有足够多的点是可见的，即使只是从一个视角，我们都可以解决它在三维空间的位置和方向。”
Ultimately, the bands would be placed around each body part of the actor; the upper arm, lower arm, upper leg, lower leg, waist, shoulder, head, chest. Then each band was modeled as a piece of geometry wrapped around an oval.The result – as Knoll and Hickel had hoped – was thatILM could track the motion from a minimal number of cameras, greatly reducing the footprint on set.
最终，这些带子将被放置在演员身体的每个部位;上臂，下臂，上腿，小腿，腰，肩，头，胸。然后，每个条带被建模为一个椭圆形包围的几何图形。结果——正如Knoll和Hickel所希望的那样——ILM可以用最少的摄像机跟踪运动，大大减少了拍摄现场的足迹。
Davy Jones actor Bill Nighy, and other actors playing his crew, wore IMocap suits during filming on Dead Man’s Chest and At World’s End (the two sequels were filmed back-to-back), which took place all the way from controlled sound-stages to sunlit and water-affected outdoor shoots.“For most of the Pirates films,” details Knoll, “we only had one or two witness cameras and the plate camera. Many shots were solved from a single camera view.”
Davy Jones饰演的Bill Nighy和其他剧组演员在拍摄《加勒比海盗：聚魂棺》(Dead Man’s Chest)和《加勒比海盗：世界尽头》(World’s End)时都穿着IMocap套装(两部续集都是背对背拍摄的)。对于加勒比系列大多数的电影来说，我们只有一两个现场目击者摄像机和素材摄像机。很多镜头都是用一个角度的摄像头解决拍摄问题的。”
The IMocap suits featured bands with white dots on black squares.This was chosen, says Knoll, because “we knew thatthe pattern would often be out of focus or motion blurred, and using a circular dot meant that it would still be trackable even when out of focus or blurred.”
IMocap套装的特点是黑色方块上有白点的圆点。Knoll说，之所以选择这种方式，是因为“我们知道，图案往往会偏离焦点或运动模糊，而使用圆形圆点意味着，即使在偏离焦点或模糊的情况下，图案仍然可以被追踪。”
Knowing that the shooting environments forPirates 2 and 3 would sometimes be very dark, ILM originally employed LEDs under the white dots to make them glow in the dark. “This worked very well in tests, but on set it became impractical with the number of characters we were dealing with,” says Knoll. On Van Helsing (2004),ILM had designed and built custom active IR tracking markers for its performance capture suits, however, given the scenarios expected in Pirates 2 and to simplify the system, it was decided that we forgo the LEDs and simply find the most high-contrast material possible, with a matte finish to avoid specular highlights.”
由于知道《加勒比海盗2》和《加勒比海盗3》的拍摄环境有时会非常黑暗，ILM最初在白点下使用led使它们在黑暗中发光。Knoll说:“这在测试中运行得很好，但在片场，我们要处理的字符数量变得不切实际。”在2004年的一个电影《范海辛》中,ILM已经设计并建造定制主动红外跟踪标记为其表演捕捉服装,然而,鉴于加勒比海盗第二部和简化系统,我们决定放弃发光二极管和简单地找到最高对比度的材料,避免高光问题。
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