Linear Workflow: A Guide线性工作流程：入门指引

Linear Workflow: A Guide线性工作流程：入门指引
By Dave Fleet
作者：Dave Fleet
Software used使用软件:
3ds Max, V-Ray
翻译by:yipinsucai.com

This has been the subject of discussions on many forums over recent years. I realized that there were all sorts of tutorials offering often conflicting information regarding the process. This is not the only way, just my way. I would like to thank my mates Ben Cowell and Phil Shoebottom for offering some clarity on a few points.
这个问题的讨论在最近几年已经遍布许多论坛，我意识到有各种各样的教程提供相关的信息，但是往往相互矛盾。这不是惟一的方法,只是我的方式。我要感谢我的队友 Ben Cowell和Phil Shoebottom提供一些明确几个要点参考。
What is "Linear Workflow”?
什么是线性工作流程？
Look at Fig.01. What is the difference between the image on the left and the image on the right? The truth is; nothing at all, except the way your monitor is showing you the image.
看Fig.01，,左边的图像和右边的图像有什么区别?事实是,没有任何区别，除了你的显示器的显示方式。

Fig. 01
V-Ray and 3ds Max process the data in which to make an image in "linear space”, also known as Gamma 1.0, but by default all monitors show you the image with a Gamma of 2.2 (sRGB), which basically makes the image look dark, although it actually isn't dark at all. The program just assumes that you are viewing the image with Gamma set to 1.0, instead of 2.2, until you tell it otherwise.
vray和3ds Max通过处理数据在“线性空间”来创造出一个图像,也被称为伽马1.0,但默认情况下所有的显视器显示的图像是伽马2.2(sRGB),它基本上会使得图像显得黯淡,尽管它实际上不是暗淡的。程序假定您正在查看图像伽马设置为1.0，而不是2.2，除非你告诉它。
Unfortunately this has always been the case with 3D rendering, which means that many artists who don't know about linear workflow learn to light scenes by using a handful of tricks to try and get results you'd expect in real life.
不幸的是3 d渲染一直都是这样,这意味着许多艺术家不了解的线性工作流程，而学会通过大量的伎俩试图得到正确的像现实世界中你所期待的结果。
Things like adding more lights, boosting the Environment/GI levels to incredibly high values, adding some ambient lights with shadows turned off, etc.
诸如添加更多的灯光,提高环境光或 GI的值到难以置信的高值,添加一些环境光源与关闭阴影,等等。
This all adds to the amount of calculations being made by the renderer for no real reason, as all of the data is in fact already there, providing you tell the program to show it to you correctly.
这一切都毫无理由地增加了渲染工作的工作量和电脑的计算量。其实所有的数据实际上已经在这里了，只要你告诉程序去正确地显示出来
Setting up 3ds Max/设置3ds Max
As well as the image itself, textures and materials also need to be correctly converted to Gamma 2.2. Note that V-Ray will ignore all of the Gamma settings in the 3ds Max dialog. We do this step in order to set up the Material Editor to render its thumbnails with linear workflow so that we get an accurate representation of what materials in our render will look like. It's worth noting that you can render in linear space in V-Ray without touching these setting at all, but you won't be able to use the Material Editor thumbnails to accurately tune your shaders.
图像本身以及贴图和材质也需要被正确转换成伽马2.2。注意,vray会忽视所有的在3dsMax内部的伽马设置。我们做这一步是为了设置材质编辑器使它用线性工作流程来显示，为了获得一个准确的材质描述。值得注意的是,你可以用VRAY在线性工作流程里完全不改变这些设置,但是您不能使用材质编辑器的缩略图来准确调节您的材质。
Go to Customize > Preferences > Gamma and LUT. Change the settings to those shown in Fig.02.
打开 Customize > Preferences > Gamma and LUT. 改变设置如图in Fig.02.

Fig. 02
As I said, V-Ray ignores the Gamma settings, but it doesn't ignore the Input Gamma in the Bitmap Files box. By setting this to 2.2 you will globally effect how textures are loaded in. Don't change the Output Gamma as this will burn in the Gamma correction to rendered images, which limits what you can do to the image in post.
就像我说的,Vray忽略了伽马设置,但它并不忽视输入伽马。通过将该变量设置为2.2,您将在全局范围内作用于加载纹理。不要改变输出伽马,因为将使用伽马校正来渲染图像,否则它将限制在后期所能做的。
Most images you find on the internet or from your digital camera will be sRGB (Gamma 2.2) already so it is just easier to assume 2.2 from the beginning. Some files are natively linear (like HDRIs) so will not require correcting to 2.2; you also do not want to correct Normal maps or Displacement as they won't work properly. For these images the best thing to do is override the Gamma settings on a case by case basis as you import them into your scene (Fig.03).
大部分在互联网上找到的或用你的数码相机拍摄的的图片都是sRGB模式(伽马2.2)，所以一开始就假设伽马是2.2对以后的工作更方便。一些文件天生就是线性的(如HDRIs)，所以不需要修正至2.2。你也不需要调节法线贴图或置换贴图否则它们将不能正确地工作。使用这些图片最好的方法就是一开始就设置好全局的伽马，然后它们一导进来就自动使用你设置好的伽马(fig03)。
翻译by:yipinsucai.com

Fig. 03
3ds Max is now set up correctly, so set up your scene and create a render using the V-Ray Frame Buffer.
3ds Max 的设置现在就是正确的了，然后设置你的渲染场景然后用V-Ray Frame Buffer来渲染。
Setting up V-Ray/设置VRAY
First step, go to V-Ray's Color Mapping dropdown menu, change the Gamma to 2.2 and tick Don't affect colors (adaption only) (Fig.04).
第一步，找到vray的Color Mapping展卷栏，把伽马设置为2.2并且勾选Don't affect colors (adaption only) (Fig.04).

Fig. 04
The advantage of ticking Don't affect colors (adaption only) is that the Gamma 2.2 will not be burnt in to the final image, however V-Ray will proceed with all its calculations as though color mapping is applied. In effect this enables V-Ray to calculate better noise samples as it is sampling a brighter image, so the differences between light and dark tones are easier to detect.
勾选Don't affect colors (adaption only)，伽马2.2将不会计算最终的渲染图片，当然了vray计算的时候仍然会按照正常的color mapping。实际上,这使得vray计算的时候能更好的采样,因为它会按照计算一张很亮的图片来计算采样,所以亮部和暗部之间的差异能更容易地检测。
The image you save out is still linear, so we still have the flexibility of compositing in linear space.
你存的图片仍然是线性的，所以我们需要在线性空间做一些调节。
The V-Ray Frame Buffer also ignores the 3ds Max Gamma settings, so the render may come out looking very dark. You will need to click the sRGB button at the bottom, which is V-Ray's own Gamma correction. Note that this is only for displaying purposes; the image is still linear. As you can see, Fig.05 – 06 is now displaying a linear image corrected to be viewed at Gamma 2.2.
vray渲染帧缓存同样忽略MAX的伽马设定，所以渲染结果看起来会很暗，你需要点击srgb按钮在按钮栏，那才是vray自己的伽马校正，提示一下，这个只是显示效果，图片仍然还是线性的。如图Fig.05 – 06展示了一张线性的图片被校正到伽马2.2的效果。

Fig.05

Fig.06
You will notice that from now on light will fill every corner of the image without the need to add a load more lights or boost any settings to unnatural levels. You will also notice that the image will not burn out nearly as much as before. This is basically because when you want to brighten the dark areas by adding more lights, this still contributes to the light areas, so you will inevitably end up with ranges that exceed pure white (255, 255, 255).
您将注意到,从现在起,光线会填满每一个角落而不需要添加更多光或增加任何不自然的参数设置。您还会注意到,图像不会像以前那样样经常过爆，这基本上就是因为当你通过添加更多的灯来照亮黑暗的区域的时候同时也影响到了亮部区域的灯光照明，所以你将会不可避免地出现超过纯白色(255、255、255)的亮度范围。
翻译by:yipinsucai.com
File Formats and Rendering/文件格式和渲染
Compositing in 32-bit has been used in feature films for years. Color correction is much more flexible, especially when controlling highlights. The ideal solution is to export a linear image like EXR or DPX for example. With linear images all of the pixel data is mathematically correct as opposed to looking correct, resulting in accurate and predictable results when adding or multiplying in post. After Effects and Nuke can be setup to view linear images in sRGB colorspace, composited in 32-bit and then exported at 8-bit for broadcast.
合成使用32位图像已使用多年了。色彩校正灵活得多,尤其是高端控制。理想的解决方案是输出一个线性图像像比如EXR或DPX。线性文件所有的像素数据在数学上是正确的而不是看起来正确的，从而可以准确地获得在后期中的结果。在After Effects 和 Nuke可以设置图像在sRGB色彩空间为线性影像，合成使用32位,然后输出的时候用8位。
When saving linear images, 8-bit formats will most likely result in some color banding. There often isn't enough range in 8-bit colourspace to represent a complete tonal range when working with linear images. So whenever possible always render out to either 16-bit (TIFs or SGIs) or 32-bit (EXRs, DPX).
当储蓄线性图片时,8位格式将可能导致一些色带。通常8位的图片在处理线性图像时并没有足够的数据量来表现一个完整的色调范围。所以只要可能存储渲染图片时用16位(TIFs或SGIs)或32位(EXRs,DPX)。
Never use JPEGs for rendering as JPEG compression is optimized for nonlinear images and will throw away much of the data required for Gamma translations to and from linear space.
永远不要使用jpegs，因为jpegs已经被压缩过了，不是线性的图像了，而且丢失了很多后期伽马调整时所要用到的数据。
Burning the Gamma in
Burning the Gamma in will limit what you do in post, but if you want to then simply un-tick Don't affect colors (adaption only) in V-Ray's Color Mapping dropdown menu (Fig.07).
Burning the Gamma in 需要你在渲染完以后点击SRGB按钮，但是如果你想简单点，你只要把Don't affect colors (adaption only)选项去掉勾选就行了。

Fig. 07
You can tell this has worked because you can view the same image, but without having to click the sRGB button in the V-Ray Frame Buffer. You will notice that if you click the sRGB button it will preview Gamma correction on top of that, resulting in a washed out image (Fig.08). You get a similar result if you duplicate the image to the Max Frame Buffer. This is because we set Max to Gamma 2.2.
你会看到这个已发挥了作用,因为如果你不点击vray帧缓存里的sRGB按钮您也可以看到相同的图像。如果你点击按钮时,它将预览sRGB伽马校正的效果并导致一个过亮的图像(fig08)。如果你把图像复制到max默认的帧缓存，也会得到同样的过亮效果，这是因为我们设置了MAX的伽马为2.2。

The Magic Linear Workflow Button/一键转换线性流程按钮
This button is a little misleading. It looks like if you tick it, then you will magically get proper linear workflow… but no, you don't. This button is basically a quick and brutal way of correcting the V-Ray materials that were not setup and tuned with linear workflow in mind. I wouldn't use this (Fig.09).
这个按钮容易让人产生误解，看起来如果你开启了这个，你就会自动把场景转为线性工作流程，其实不是的。这个按钮是硬生生地把vray材质转换成线性工作流程，是粗暴的肯定不是你想要的，反正我是肯定不会用的。

Fig. 09
以上是全部教程。
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