杂谈：关于特效
原文节选自《驯龙高手设定集》，由龙崖社·龙之书翻译组汉化整理，本合集仅供Bilibili，爱发电（最先更新），Lofter平台龙崖社社团官方账号发布，未经授权禁止转载！
特效团队负责创造CG电影中角色动画之外的所有与运动相关的元素。考虑到《驯龙高手》中描绘的动作规模，这一职责需要耗时耗力的、专注的努力。除了明显的喷火龙的特效，该团队还负责制作复杂的火焰破坏，大规模的岩石碎裂，和可交互的云彩效果。
喷火龙对他们的目标造成巨大的火焰破坏，所以特效团队必须想出有效的方法点燃道具和布景。该团队基本上建造了火焰基元方块，就像按扣式玩具建筑装置一样，可以根据需要固定在屋顶、船上或树上。这些方块的放置经过深思熟虑，以展示火焰包裹了它的主道具。“看到火在这些环境中相互作用和卷裹是非常重要的。“我们的火有有机形状的发射图案，因此它可以包裹物体，创造出更真实的外观，我们在电影中的所有火盆上也使用了这种图案。”特效指导马特·贝尔解释道。
龙引起的岩是破碎另一个关键特效。为了刻画红死神破岩而出、山体崩裂的场面，团队在岩壁里面建造“饼干切割机”把它裂成碎片。拜耳说：“首先，我们在岩石模型表面覆盖满种子粒子，然后将这数千个可覆盖的对象输入刚体模拟器里。之后我们分配各种选项，比如大小不一的页岩碎屑、沙子或火山岩碎片，当两个拼合在一起的碎片断裂的时候，我们就让它爆发出大量的这种元素。“为了配合这一特效，特效团队开创了一种立体渲染的新技术，堪称本片的开创性成就。
虽然云一般是由天空中的水蒸气形成，但在电影里，它们是由特效、灯光、和数字绘景团队制作的。在小嗝嗝和无牙在云层中飞翔的部分镜头里，一簇簇球体的云就像一串串葡萄，首先它们被放到适当的位置，然后是数字绘景师门“设计精美、细致的绘画作品让它们看起来像
云。因为图像存在于3D空间中，随着摄影机的移动，那些图像也会相应移动，形成视差，就像真正的云一样，”视觉效果主管克雷格.琳说。特效和灯光团队也用发光的半透明物填充这些云，给大气层一种梦幻的感觉。
人物和云彩发生实际接触的时候，特效团队制作了，可以跟人互动的积雨云。这些元素管理起来更具挑战性，因为它们有不同的细节变化：在单个云中，它们可以从纤细到更具结构性，就像我们看到的小嗝嗝、无牙、亚斯翠一起飞翔的镜头里的拱形云彩，云层透出来的光必须根据需要调整强弱和大小。特效指导马特.拜耳说：“我们使用自定义着色器结合立体渲染技术，从而达到云层密度和光亮的平衡，调和不同细节处的光源。”
事实证明，综合多种特效的镜头——比如电影结局中的红死神之战，当红色死神最后释放了他的强大的火焰时，空中翻滚着像凝固汽油弹燃烧浓密的黑烟，整个画面布满了火焰——由于巨大的文件，给宣传的工作带来了极大的难度。“我们的解决办法是通过两位分别位于格伦戴尔工作室和一个北加州POI工作室的特效开发师共同编写一个新的渲染。我们最终在超过1/3的镜头里使用了这个程序。”特效指导马特.贝尔回忆道。另外，以前的渲染工具需要把背景元素分层，但在立体动画电影里，这种设置在银幕上看起来就像一堆卡片，事实证明，这个程序在各个层面都发挥了重要的作用。
原文：
The effects team is charged with creating all elements with motion outside of character animation in a CG film.Considering the scale of action portrayed in How to Train Your Dragon, this responsibility required ambitious, focused effort. Beyond the obvious fire breathing dragon complexities , the team was also responsible for producing complicated fire destruction, extensive rock shattering, and interactive cloud effects.
Fire-breathing dragons inflict massive fiery destruction upon their targets, so the effects team had to come up with efficient ways to ignite props and sets. The team essentially built modular fire blocks that, like snap on toy building sets, can be stuck on a roof, boat, or tree as needed. These elements are placed thoughtfully to show fire that Envelopes its host prop." Seeing the fire interact and curl around these environments was really important. Our fire has organic shaped emmission patterns so it can wrap around objects to create a more authentic look, which we use on all the braziers in the film as well," explains Head of Effects Matt Baer.
Dragon-induced rock shattering was another key effect. To portray the damage incu rred by the Red Death smashing through a volcanic rock wall, the effects team built "cookie cutters" into the cliff wall to break it up into fragments. "First we paint seed particles all over rock models and feed thousands of them into rigid body simulators, which can be layered. We then assign options such as variably sized shale rock debris, sand, or pyroclastic dust, and where each of the cracks between the pieces propagate, we blast out huge emissions of these elements," explains Baer. This effect required the development of new technology for volumetric rendering- an appropriately "ground-breaking" accomplishment for this film.
While clouds are generally made by water vapor in the sky, here they are made by the effects, lighting, and matte painting teams. In several sequences where Hiccup and Toothless fly through the clouds, simple clusters of spheres- almost like a bunch of grapes-are placed in space and then matte painters "project beautiful, detailed paintings onto them to make them look like clouds. Since the paintings exst in 3D space, as the camera moves around, they move and parallax just like real clouds do," explains Visual Effects Supervisor Craig Ring. The effects and lighting teams also fill these clouds with a glowing translucency to give a magical look to the atmosphere.
For sequences in which characters actually come in contact with clouds, the effects team created cumulonimbus clouds with which they can interact. These elements are more challenging to manage because they requ ire varying detail: Within a si ngle cloud, they can range from wispy to more structural, like the archways seen in the ·flight that Hiccup and Toothless share with Astrid. The amount of Iight that scatters with in them must also be dialed up or down as needed, and "we achieve the desired balance of density and light by using volume rendering with custom shaders that allow us to blend from one frequency of detai I to another," says Head of Effects Matt Baer.
Putting multiple effects together in shots- such as during the big battle at the end of the film, when the Red Death finally unleashes his powerful fire and the sky fills with big, napalmlike, churning smoke illuminated by fire and haze in full frame- proved to be an enormous challenge to render, based on huge file sizes. "We solved this by having two effects developers, one in the Glendale Studio and one in the Northern California POI facility, work together to write a new render program, which we ended up using in more than one-third of our effects shots," recalls Head of Effects Matt Baer. Also, previous rendering tools would call for the layering of atmospheric elements, but in a stereographic film, such a setup would look like cards on the screen, so this new system proved important on several levels.
