Screen space Reflections 屏幕空间反射 后期处理系列7

Screen space Reflections 屏幕空间反射

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Unity2018.3版本
参考链接：https://github.com/Unity-Technologies/PostProcessing/wiki/Screen-space-Reflections

Screen-space Reflection is a technique for reusing screen-space data to calculate reflections. It is commonly used to create more subtle reflections such as on wet floor surfaces or in puddles. Because it fully works in screen-space it can only reflect what’s currently on the screen (no backface reflection, no object living outside of the screen).
屏幕空间反射是利用屏幕空间数据进行计算反射的一种技术。它通常用于创建更精细的反射，如在潮湿的地板表面或水坑。因为它完全在屏幕空间中工作，所以它只能反射当前屏幕上的内容(没有背向反射，屏幕外没有对象)。

Screen-space Reflection is an expensive technique, but when used correctly can give great results. It is only available in the deferred rendering path as it relies on the Normals G-Buffer.
屏幕空间反射是一项昂贵的技术，但如果使用得当，可以产生很好的效果。它仅在延迟渲染路径中可用，因为它依赖于法线G缓冲区。

The current implementation of Screen-space reflections in Unity is tuned for performance over quality to make it usable in production on current-gen consoles and desktop computers. Be aware that this technique isn’t meant to be used to get perfectly smooth reflections, you should use probes or planar reflections of that. This effect is also great at acting as a specular occlusion effect by limiting the amount of specular light leaking.
Unity中屏幕空间反射的当前实现是针对性能而不是质量进行调整的，以使其在当前的主机和桌面计算机上可用。请注意，这种技术不是用来获得完美的平滑反射，您应该使用探针或平面反射。这种效果还可以通过限制高光的泄漏量来起到高光遮蔽的作用。

Properties

Property	Function
Preset	Quality presets. Use Custom if you want to fine tune it.
预设	质量的预设。如果您想对其进行微调，请使用Custom。
Maximum Iteration Count	Maximum number of steps in the raymarching pass. Higher values mean more reflections.Note: only available with the Custom preset.
最大迭代数	步进pass中的最大步数。更高的值意味着更多的反射。注:仅适用于自定义预设。
Thickness	Ray thickness. Lower values are more expensive but allow the effect to detect smaller details.Note: only available with the Custom preset.
厚度	射线厚度。较低的值比较昂贵，但是允许检测较小的细节。注:仅适用于自定义预设。
Resolution	Changes the size of the internal buffer. Downsample it to maximize performances or supersample it to get slow but higher quality results.Note: only available with the Custom preset.
分辨率	更改内部缓冲区的大小。向下采样，以最大限度地提高性能，或向上采样，以获得缓慢但高质量的结果。注:仅适用于自定义预设。
Maximum March Distance	Maximum distance to traverse in the scene after which it will stop drawing reflections.
最大步进距离	在场景中移动的最大距离之后，它将停止绘制反射。
Distance Fade	Fades reflections close to the near plane. This is useful to hide common artifacts.
距离消退	淡出近平面的反射。这对于隐藏公共组件的反射效果非常有用。
Vignette	Fades reflections close to the screen edges.
装饰	淡出靠近屏幕边缘的反射。

Performances

You should only use the Custom preset for beauty shots. On consoles, don’t go higher than Medium unless you have plenty of GPU time to spare, especially when working at full-hd resolutions. On lower resolutions you can boost the quality preset and get similar timings with a higher visual quality.
您应该只使用自定义预设的精彩镜头。在游戏机上，除非你有足够的GPU时间，否则不要超过中等，尤其是在全高清分辨率下。在较低的分辨率下，您可以提高质量预设，并获得类似的时间与较高的视觉质量。

Known issues and limitations

• Screen-space reflections doesn’t support AR/VR.

Requirements

• Compute shader
• Motion vectors
• Deferred rendering path
• Shader Model 5.0