3D Compositing Guide (Part 01)-3D合成指南（第一部分）cwws 翻译

cwws

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片子地址；http://www.simonreeves.co.uk/diversion-film/

3D Compositing Guide (Part 01)
3D合成指南（第一部分）

Before I start I should say that this is based on what I know and learnt from people at uni, and at work, and the internet.

在我开始之前，我想说这些都基于我从UNI，工作中以及互联网上向人们学习获得的知识。

Other people you may learn from prefer more or less passes etc. for more control or to save on excess files - so just keep in mind there are usually different ways to do things all with their own advantages and disadvantages (and don’t blame me).
In this tutorial I’ll be using examples from a couple of shots from our short film ‘Diversion’. Directed by myself and Aidan Gibbons

你所了解的别人或许倾向于更多或更少步骤，以取得更大的控制权或者节约过剩的文件量，-不过请牢牢记住这些不同的做法通常都有他们各自的优点和缺点，（所以请别因为我的做法和别的不同而责怪我。）

在这个教程里，我想会用到一些镜头，来自于我和Aidan Gibbons 一起导演的电影短片：‘Diversion’
Types of Passes
Passes的种类（这里的Passes是指渲染得不同效果层，比如阴影，高光，反射等等———译者注）
If you want very fine control in post over every element of the scene, you could render the the objects in tons of passes with a different one for every element in the render, ambient texture, different light passes, shadows, reflection, refraction, GI the list goes on.but generally thats not really necessary.

如果你希望很好的控制场景里面的每一个物体，你可以把每一个物体单独渲染，同时渲染出好多不同的Passes层。比如mbient texture（环境材质）, different light passes（不同的灯光层）, shadows（阴影）, reflection（反射）, refraction（折射）, GI（全局光），等等，这个列表可以继续排下去，但是，通常，这些并不是真正需要的。

So if you like you may want to include lighting/shadows/specular/GI all in this one pass and maybe just add a couple of additional passes to this ‘Beauty’ pass.

所以如果你愿意，你可以把lighting/shadows/specular/GI（灯光/阴影/高光/全局光）包含在一个Pass里面，另外或许只需要再增加一两个额外的Passes到这个“漂亮”的Pass里面就行了。
For compositing with live action in ‘Diversion’, we generally used a standard set of passes on all shots, and then on some shots we needed some other specific passes to help out with mattes, masks and the like - which I’ll try and mention a couple of later.

So here is an example from excitingly named ‘Shot14′.
First of all, here is the background plate from the footage:

在为实拍的电影‘Diversion合成的时候，我们通常为所有的镜头使用相同一套标准的Passes设置，然后在某些镜头上我们会需要一些特殊的Passes来帮助我们制作遮罩，Masks和后面我将会提到的一些技巧，所以这里就有一个例子是关于令人兴奋的镜头，叫做“Shot14”。
首先，这里是一个地板像镜子一样光亮的背景序列：

Don’t think there’s much to explain on that one.
这个基本上没什么好解释的，
Beauty (RGBA could be named ‘Diffuse’ or ‘RGB’ perhaps)
（需要RGBA通道，一般会被叫做为Diffuse或者RGB层）

This is the base for the cg elements in the shot, and it can vary a lot what is included in this pass.

上图是这个场景中最主要也是最基础的CG元素，包括这个RGBA的Passes，它可以有很大的变化。

Our standard beauty pass included shadows cast onto the objects but not shadows cast onto the plate (separate pass for them) but as there isn’t any shadows in this shot, I won’t go into why now.

我们标准的完美的Pass需要包括物体投射在彼此上面的阴影层，但是不包含物体投射在地面上的阴影层，（需要把这两个阴影分开为不同的Pass），但是，在这个场景里面是没有任何阴影的，我现在先不说我们该怎么创造这些阴影。

When we light the diffuse pass, I find it helps to make it a bit brighter than you want in the final shot, especially to take into account the ‘Ambiant Occlusion’ (or ‘Dirtmap’) pass which adds the darker areas in this shot.

当我们照亮不同的Pass获得灯光层，我会发现在最后的镜头效果里，它会帮着把镜头调得比你预期的要更加亮一点，特别是把‘Ambiant Occlusion’ (or ‘Dirtmap’)层加在这个镜头比较暗的区域的时候。

Specular Pass (RGB, Alpha channel not needed)
（不需要Alpha通道的RGB图像）

 This pass is for specular only, and is layered over the top of the beauty pass with ’screen’ (or you could ‘add’ (additive) it). Screen or Add basically remove all the black in the pass, leaving just the highlights (the specular in fact.)

This is the same for a Reflection pass, and if you want to render a light in a separate pass - as again you just want to hide all the black pixels values and keep the white values.

这个层只用于高光调整，同时它被放在完美的Pass设置的上层，并且给与Screen层叠模式（或者你可以用Add模式）。用这两个模式可以去除这个Pass所有黑暗的部分，只留下高光部分，实际上的specular（镜面反射高光）部分。

Reflection Pass (RGB, Alpha channel not needed)
（不需要Alpha通道的RGB图像）

Whoops, I seem to have got a little ahead of myself there. Anyway this reflection pass, is on the plate, so instead of compositing it onto the last two passes, we can lay it straight onto the plate. Smashing.

噢，我似乎有点赶超我预先订下的进度了，无论如何，这是地面上金属板的反射层，所以不用把它放到上面两个金属板层之上，取而代之我们可以直接把它放到地面层上面。

Reflection Matte Pass (RGB, Alpha channel not needed)
（不需要Alpha通道的RGB图像）

Now you can’t just slap the reflection onto the plate in this instance, because there are already reflections on the floor that would be occluded by the signs were actually there (they would block them).

但是现在你不能直接把反射拍到地面上面，因为地板上的反射会被金属牌子的形状遮挡住

So I found a good way to create a matte for where the reflections will be is to make a pass where the signs materials to a constant white material, and have that as the only thing reflecting in the scene.

所以我发现了一个很好的方法来创建一个遮罩，来遮挡一部分的反射，这需要用金属牌子来获得一个赋予了白色材质的层，然后用它来作为场景中唯一反射的物体。

N truthfully in the film I made the objects black, and rendered them on a white surface and a white environment - but now I realise that is way to overcomplicated as you can just invert it.

说实话，在电影里面我是把这个物体弄黑，然后在一个白色的表面和白色的环境下面渲染它们，但是现在我明白了，那个方式可以变得更加简单，只要你把环境和物体的颜色颠倒一下就成（也就是上一段说的物体白，环境黑。）

You can multiply this pass onto the plate before the main reflections to matte out those reflections you don’t want.

你可以复制这个Pass，并把它放在在主要反射层之前，背景地面之上，使得你不想要的反射部分被遮住。

Another note about the reflections I’m afraid. If you look at the plate, you can see the differences between the soaked floor, and the standing water/puddles, the puddles are sharp reflections while where the water has soaked in, the reflections are blurred.
So before those passes are rendered I painted a matte based on the plate - and used a camera projection to apply that texture onto the floor, to control the amount of blur for the reflection.

另一个关于反射我担心的问题是，如果你仔细看地面，你会发现地面上潮湿的部分和小的水坑，他们的反射式不同的，水坑的反射非常直接税利而潮湿地面的反射则有些模糊，所以在渲染这些Passes之前，我花了一张基于地面不同区域的遮罩图片，然后使用Camera Projection（摄像机投射）来给地面赋予一种材质，通过它来控制地面反射的程度。

Hopefully that made sense.

希望这些能说明问题。
Ambient Occlusion (RGB, Alpha channel not needed)
（不需要Alpha通道的RGB图像）

This pass effects the CG elements as well as the plate (although often you may want to render 2 separate AO Passes), so to layer it onto both, before this we need to layer the CG passes we have so far, over the plate (including the reflections).
For this pass, we just want to keep the darker values, so to remove/hide the white, we will use ‘Multiply’.

这个Pass同时对CG元素和背景地面起作用，（或者你经常会把他们分开来渲染，地面归地面，CG物体贵CG物体），然后把他们分别放到两者上部，在这之前，我们首先需要放好我们已经拥有的所有CG渲染层在地面背景层之上（包括反射层）

对于这个Pass而言，我们只需要它的暗部，所以为了去除/隐藏白色的亮部，我们使用Multiply层叠方式。

ID Pass (RGBA)
（需要RGBA通道）

This should come earlier in the comp, I mainly use it to colour correct the diffuse pass before anything else is layered on top (so maybe earlier in this guide? But its a bit special so I thought I’d leave it till now). This is a very useful pass for making multiple matte’s (masks) in one pass.

这个实际上因该早一点就说明的，我主要用它来做不同Pass的校色，它需要在任何渲染层之前放在CG元素上面一层（就是说紧贴着CG层，所以或许我应该一开始就在教程里面讲这个部分的，但是因为它有一点特殊，所以我把它留到现在才讲。）这是一个非常有用的Pass，在一个Pass渲染层中创建出多种遮罩（Masks）

By giving certain objects materials that are either, 100% Red, 100% Blue or 100% Green we can extract just one of these channels (R, G, or B) in post as a matte to do colour correction on specific objects or whatever you please. As you can see by this gif below, which cycles through the RGB, then Red, then Green, then Blue channels.

通过给于特定的物体特定的材质，比如100%红，100%蓝，100%绿，我们就能通过在合成时扣出相关的通道（R, G, or B）来产生一个遮罩进行对特定物体或任何你喜欢的部分的校色或调色，你可以看下图，依次通过红色，绿色没，蓝色通道得到的结果。

If you’re feeling fancy you can use the A channel too, currently the A channel will show the objects that are in the R,G,B channels (as they have an alpha of 1 / 100%), but if you assign everything else a black material with an alpha of 1, you could specifically assign some objects with a black material with alpha 0.
Hope that made sense, don’t have any images for that at the moment. 

如果你感觉非常奇怪，你也可以就用一个通道来表示，现在这一个通道会显示物体在RGB通道上的样子，（当他们有一个1 / 100%的Alpha通道），但是如果你给物体赋予任何除了黑色材质的

Alpha值为1的材质时，你可以特别地赋予另一些物体黑色的材质，并且把Alpha值设为0。
希望你能明白我上面的说明，不过这里没有任何的图来解释我上面的话

If you want to watch the shot, and the film infact you can find it here: Diversion Film Website..
如果你想要看这个完成的镜头，和实际的影片，你可以在这里发现它：Diversion Film Website..

Hopefully I will write another part to this if its useful about the actually comping process, Multiplying/Adding/Over using ID mattes and so on.

如果这些对实际的合成有帮助的话，希望我会再写另外一部分，主要关于Multiplying/Adding/Over层叠模式和使用ID遮罩等等的内容。

I personally use the FxTree within XSI but Shake/Nuke/Combustion are all the same principles so it shouldn’t be a problem.

我个人使用XSI内部的FxTree合成系统，但是Shake/Nuke/Combustion都是基于同样的原理，所以你把以上方法运用到别的软件上面应该不是问题。

If you see any mistakes or have any comments please email me or use the comments thing on here - Cheers.

如果你发现任何错误或者有任何的建议，请给我发邮件或者使用这里的留言功能，谢谢了。