Auto Exposure 自动曝光 后期处理系列10

Auto Exposure 自动曝光

本文档主要是对Unity官方手册的个人理解与总结（其实以翻译记录为主：>）
仅作为个人学习使用，不得作为商业用途，欢迎转载，并请注明出处。
文章中涉及到的操作都是基于Unity2018.4版本
参考链接：https://github.com/Unity-Technologies/PostProcessing/wiki/Auto-Exposure

In ocular physiology, adaptation is the ability of the eye to adjust to various levels of darkness and light. The human eye can function from very dark to very bright levels of light. However, in any given moment of time, the eye can only sense a contrast ratio of roughly one millionth of the total range. What enables the wider reach is that the eye adapts its definition of what is black.
在眼睛生理学中，适应性是指眼睛适应不同程度的黑暗和光亮的能力。人眼可以在非常暗到非常亮的光线下工作。然而，在任何给定的时刻，眼睛只能感知到大约百万分之一的对比度。眼睛适应了黑色的定义范围，这使得它的适应更广。

This effect dynamically adjusts the exposure of the image according to the range of brightness levels it contains. The adjustment takes place gradually over a period of time, so the player can be briefly dazzled by bright outdoor light when, say, emerging from a dark tunnel. Equally, when moving from a bright scene to a dark one, the “eye” takes some time to adjust.
根据图像所包含的亮度范围可以动态调整图像的曝光效果。这种调整是在一段时间内逐渐进行的，所以当玩家从黑暗的隧道中走出来时，他们可能会被室外明亮的灯光短暂地眼花缭乱。同样，当从一个明亮的场景切换到一个黑暗的场景时，“眼睛”需要一些时间来调整。

Internally, this effect generates a histogram on every frame and filters it to find the average luminance value. This histogram, and as such the effect, requires Compute shader support.
在内部，这种效果在每一帧上生成一个直方图（柱状图），并对其进行过滤，以找到平均亮度值。这个直方图，以及它的效果，需要计算着色器的支持。

Properties

Exposure settings:

Property	Function
Filtering	These values are the lower and upper percentages of the histogram that will be used to find a stable average luminance. Values outside of this range will be discarded and wont contribute to the average luminance.
过滤	这些值是指低于或高于当前帧直方图中用于找到稳定的平均亮度的百分比。超出此范围的值将被丢弃，不会影响平均亮度。
Minimum	Minimum average luminance to consider for auto exposure (in EV).
最小值	自动曝光(曝光值)要考虑的最小平均亮度。
Maximum	Maximum average luminance to consider for auto exposure (in EV).
最大值	自动曝光(曝光值)要考虑的最大平均亮度。
Exposure Compensation	Middle-grey value. Use this to compensate the global exposure of the scene.
曝光补偿	补偿值。用这个来补偿场景的总体曝光度。

Adaptation settings:

Property	Function
Type	Use Progressive if you want the auto exposure to be animated. Use Fixed otherwise.
类型	如果你想让自动曝光动画化，可以使用渐进方式。否则，使用固定方式
Speed Up	Adaptation speed from a dark to a light environment.
增加	从黑暗环境到光亮环境的适应速度。（仅Progressive ）
Speed Down	Adaptation speed from a light to a dark environment.
减少	从光亮环境到黑暗环境的适应速度。（仅Progressive ）

Details

Use the Filtering range to exclude the darkest and brightest part of the image. To compute an average luminance you generally don’t want very dark and very bright pixels to contribute too much to the result. Values are in percent.
使用过滤范围来排除图像中最暗和最亮的部分。要计算平均亮度，通常不希望非常暗和非常亮的像素对结果影响太多。值以百分比为单位。

Minimum/Maximum values clamp the computed average luminance into a given range.
最小/最大值将计算出的平均亮度固定在给定的范围内。

You can also set the Type to Fixed if you don’t need the eye adaptation effect and it will behave like an auto-exposure setting.
如果你不需要眼睛的适应效果，你也可以把类型设置为Fixed，它的行为像一个自动曝光设置。

It is recommended to use the Light Meter monitor when setting up this effect.
建议在设置此效果时使用光度计监视器。

Requirements

• Compute shader
• Shader model 5

See the Graphics Hardware Capabilities and Emulation page for further details and a list of compliant hardware.
有关详细信息和兼容硬件列表，请参阅图形硬件功能和仿真页面。