Unity組件：屏幕空間環(huán)境遮擋圖像特效

Screen Space Ambient Occlusion (SSAO) approximates Ambient Occlusion in realtime, as an image post-processing effect. It darkens creases, holes and surfaces that are close to each other. In real life, such areas tend to block out or occlude ambient light, hence they appear darker.

屏幕空間環(huán)境遮擋技術（SSAO）作為一種圖像的后處理特效來實時模擬場景的環(huán)境遮擋效果。

As with the other image effects, this effect is only available in Unity Pro and you must have the Pro Standard Assets installed before it becomes available.

和其他圖像特效一樣，該特效只能在Unity Pro上進行使用，并且在使用之前必須安裝Pro Standard Assets。

SSAO applied to the scene. 應用于場景中的SSAO效果。

The same scene without SSAO for comparison. Note the differences at the corners where structures or grass meet the ground.
同樣的場景，但沒有進行SSAO操作。注意兩幅圖在建筑物的角落里或草和地面的交接處的差異。

Properties 屬性

• Radius 半徑
  The maximum "radius" of a gap that will introduce ambient occlusion.
  環(huán)境遮擋所需的最大半徑值
• Sample Count 采樣點數(shù)量
  Number of ambient occlusion samples. A higher count will give better quality but with a higher processing overhead.
  環(huán)境遮擋效果所需采樣點的個數(shù)。較高的采樣點數(shù)量可以達到更高的質(zhì)量，但也會造成更高的處理開銷
• Occlusion Intensity 遮擋強度
  The degree of darkness added by ambient occlusion.
  環(huán)境遮擋所加的黑暗程度
• Blur 模糊度
  Amount of blur to apply to the darkening. No blur (0) is much faster but the darkened areas will be noisy.
  應用到黑暗區(qū)域的模糊程度。不使用模糊（0）時，處理效果很快，但黑暗區(qū)域會有需要噪點。
• Downsampling 降低采樣
  The resolution at which calculations should be performed (for example, a downsampling value of 2 will work at half the screen resolution). Downsampling increases rendering speed at the cost of quality.
  決定在何種計算下所采用的分辨率（比如， 四分之一的降低采樣將應用在一半屏幕分辨率的情況下）。降低采樣可以增加渲染速度。
• Occlusion Attenuation 遮擋衰減
  How fast occlusion should attenuate with distance.
  遮擋效果隨距離變化的衰減程度
• Min Z 最小Z軸
  Try increasing this value if there are artifacts.
  如果出現(xiàn)瑕疵，可嘗試增加該值

Details 細節(jié)

SSAO approximates ambient occlusion using an image processing effect. Its cost depends purely on screen resolution and SSAO parameters and does not depend on scene complexity as true AO would. However, the approximation tends to introduce artifacts. For example, objects that are outside of the screen do not contribute to occlusion and the amount of occlusion is dependent on viewing angle and camera position.

SSAO技術使用圖像處理特效來模擬環(huán)境遮擋的效果。它的計算開銷完全取決于屏幕分辨率和SSAO的系數(shù)，而與場景復雜度和真實的環(huán)境遮擋無關。但是，這種模擬也會引入一些瑕疵。比如，屏幕之外的物體將對遮擋效果沒有影響，并且遮擋程度取決于視角和照相機的位置。

Note that SSAO is quite expensive in terms of processing time and generally should only be used on high-end graphics cards. Using SSAO will cause Unity to render the depth+normals texture of the camera which increases the number of draw calls and has a CPU processing overhead. However, the depth+normals texture then can be used for other effects as well (eg, Depth of Field). Once the texture is generated, the remainder of the SSAO effect is performed on the graphics card.

注意SSAO技術在處理時間上來說是非常耗時的，一般應該用于高端顯卡上。使用SSAO技術會讓Unity渲染照相機上的深度+法線紋理，這樣會增加一定數(shù)量的繪制調(diào)用和一定的CPU開銷。但是，深度+法線紋理同樣也可以用于其他特效（比如，景深特效）。一旦紋理生成了，接下來的特效處理就在顯卡上進行了。

Hardware support 硬件支持

SSAO works on graphics cards with Shader Model 3.0 support (eg, GeForce 6 and later, Radeon X1300 and later). All image effects automatically disable themselves when they can not run on a particular graphics card. Due to the complexity of the effect, SSAO is not supported on mobile devices.

SSAO特效需要顯卡支持Shader Model 3.0（即GeForce 6、Radeon X1300以后的顯卡）。所有圖像特效如果無法在用戶顯卡上運行時將會自動被關閉。由于該特效的復雜性，SSAO目前不支持移動設備。