Audi A6 Avant – Hummingbird

作者 xdxu 发布于 . 分类 Commercial, Inspire, 幕后制作

Mill 公司制作的 Audi A6 Avant 汽车广告“蜂鸟”,讲述了一只机械蜂鸟(象征着 Avant 的轻巧结构)在梦境般的乡间道路上的冒险。fxguide 采访了 Mill 视效组的四位关键成员,讲述这条广告的设计、模型、动画以及合成。

fxguide 采访

fxg: 蜂鸟是如何动画的?

Montiel: 我们需要保留蜂鸟优美的运动方式(短、快),同时也要在角色运动中反射出奥迪品牌的质量。因此我们测试了不同的动态 — 用优美编舞和曲线来匹配汽车本身的优美,我们将真实的蜂鸟运动变得更有风格、更加优美。蜂鸟的 Rig 不是很复杂,我们希望保留机械蜂鸟的感觉。

fxg: 你能描述一下蜂鸟和金属蜜蜂的贴图、灯光和渲染吗?

Bussell: 贴图使用 Mari 进行绘制,蜂鸟的 anisotropic 高光对表现其真实的金属质感非常重要。

Hammond: Mari 可以在软件内建立 shader,这样不用等待最终渲染就可以看到贴图的最终效果。我们使用 Arnold 渲染,Arnold 能很好地处理高亮和高光部分的曝光(很少有杂点),在过去我们需要 clamp 灯光来去除这些杂点。

Bussell: Arnold 也能很好地处理景深和运动模糊,对于蜂鸟,三维的运动模糊是唯一可用的方案。一些渲染需要一个小时以上,但考虑到这是 HD,带全局照明、模糊反射、运动模糊、景深,我们觉得还是可以接受的。

fxg: 你们如何处理蜂鸟和蜜蜂翅膀的运动模糊?

Montiel: 从动画角度来说,我们需要测试不同的循环、不同的速度,渲染这方面也要测试不同的参数。要注意的是,镜头中鸟的大小不同,运动模糊也不同。一个 3-4 帧的循环,中间会有很多关键帧(不是在整数帧位置),这样渲染器可以读取所有的中间帧形态来得到更好的渲染结果。

Hammond: 最后我们将动画以 5 倍的慢放速度进行 cache(虽然这样 cache 花费的时间比较长),然后将 cache 导入渲染场景,恢复原来的动画速度(循环中有很多非整数帧的中间关键帧),这样可以得到更好的翅膀运动模糊。(注:蜂鸟翅膀循环如果是 3-4 帧,就意味着整数帧位置的翅膀形态和位置差异很大,这样需要很高的运动模糊 sample 来减少噪点,而且对于中间的翅膀形态没有太多的控制。)

fxg: 汽车是实拍的还是电脑制作的?

Hugo Guerra (2D lead artist): 汽车的部分和蜂鸟部分不太一样。汽车是在影棚里用 moco 实拍的,但我们尽量打平光,保持汽车没有反射和高光。然后我们跟踪摄像机,建立数字汽车(CAD 模型)。灯光渲染团队渲染数字汽车的不同 pass:高光、轮廓光、额外光、环境反射等(然后将这些 pass 与实拍的汽车合成,让实拍的汽车融入 CG 制作的环境)。

fxg: 关于合成?

Guerra: 在 Nuke 中我们使用一些脚本和 gizmo 将 EXR pass 重建,使用 position pass 和 normal pass 对局部区域进行后期照明。我们将三维摄像机和点云导入 Nuke,来控制部分镜头的 lens flare 和 volume light。我们希望广告尽量照片真实,所以参考了很多白天拍摄的照片 — 包括太阳的光晕、色散、镜头变形等。渲染结果本身已经很棒了,在后期我们加上环境的运动模糊和景深。我们使用 Arnold 提供的 pass:反射、高光、diffuse、indirect diffuse,不过我们还需要一些额外的 pass:rim pass,normal pass 等,来模拟轮廓光。

    本文概要翻译了有参考价值的部分内容,完整文章可以到 fxguide 阅读。


Mill 博客问答

Q: What was the brief given to you by Audi?

A: They wanted us to design and create a hummingbird made entirely out of car parts, as if he had actually been designed by the Audi team itself. The new Audi A6 car is built on very lightweight technology, so they wanted us to showcase all of the car’s qualities in this agile little bird.
(Rahel Makonnen – Executive Producer, 3D)

Q: What was the main challenge you faced in doing this?

A: Well, it’s very tricky to take something that exists in real life, but to have him made out of entirely different textures and materials, while still acting and moving like the real thing.
(Rahel)

Q: What was the main thing you wanted to achieve?

A: We really wanted to develop the personality of the hummingbird; this was the main tool we had to make our bird believable. He had to be friendly, he had to be cheeky and playful, he had to be elegant and at the same time he had to project all the qualities of the Audi car.
(Jorge Montiel – Head of Animation)

Q: What was the main tool you used to achieve this?

A: The Audi car itself has very elegant and clean lines, so the design had to be a simple one. This meant that the bird’s movement and body language were the main ways we could express his character. As an animator, the most challenging part of this process was working on the animatic, this is where we played around with the timing and the story, and it’s all about the story. Then, in the final animation, this is where we were able perfect the hummingbird’s body expression. It was very time consuming but it was that extra 5% where we worked on all the little details of movement and the quality of our work that made the difference.
(Jorge)

Q: How important was the compositing work in the project?

A: We had a large amount of layers to composite together in order to make the hummingbird and his world believable and realistic. Not only the bird, background and sky but we also added lost of atmospheric affects like dust and pollen and most importantly light, achieving a daytime ‘photo-real’ look was central to the hummingbird’s world.
(Hugo Guerra – Joint Head of Nuke)

Q: How big a part did light play in this world?

A: Huge! We did a lot of research on the lighting; it was one of the few ‘real’ elements we could use in this fully CG world. Our approach was to take a lot of photos taken in bright sun light and to use them as references for all the little subtle effects that happen in normal photography; the small chromatic aberrations of light, the distortion of the lens, and the small little glints of the sun hitting the metal body of the bird. Also, we really didn’t want it to be a cold and unfeeling environment, so we added a lot of warmth by introducing warm light effects and lens flares.
(Tom Bussell – Head of 3D)

Q: Was everyone happy with the result?

A: It’s an amazing piece of work to be a part of and everyone was very happy! It was a joint project with BBH and director Daniel Barber and we are always very excited to work with both of them!
(Rahel)

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