Introduction說明

Area lights in Redshift can have a predefined shape (such as rectangle, disc, cylinder or sphere) or can have their shape defined by a user-specified mesh, in which case the light is referred to as a 「mesh light」.

Area Light 形狀可以在預訂義形狀裡面進行選擇（比如：Rectangle、Disc、Cylinder或Sphere），也可以使用多邊形自定義自定光的光源形狀（Mesh Light）。

Mesh lights can reproduce lighting emitted from complex shapes like a neon sign. While a similar result can be achieved with a combination of incandescent geometry and GI, that can be considerably noisier than mesh lights.

Mesh Light的光源可以像現實中的霓虹燈一樣擁有複雜的形狀。儘管也可以用自發光幾何體結合GI達到相同的目的，但這種方式產生的噪點要高於使用多邊形光源。使用多邊形光源取代自發光幾何體在被照物體距離光源很遠時降噪優勢最明顯。

Using mesh lights instead of incandescent geometry can produce less noise, especially around on places further away from the light.

用Mesh Light取代自發光物體可以避免噪點，距離越遠越明顯。

In certain cases, mesh lights can also help optimize rendering times by facilitating the combination of multiple simple lights into fewer mesh lights.

在特定情況中，可以將一些普通光源與很少的Mesh

Light組合使用，這樣可以優化渲染時間。

Scene with 64 rectangular area lights.Rendered in 11 seconds

場景中包含64盞Rectangular Area Light。用時11秒。

Scene with a single mesh light containing 64 quads. Rendered in 2.8 seconds

場景中包含一個由64個四邊形組成的Mesh Lights。用時2.8秒

How To Use如何使用In Maya

To create a mesh light in Maya you have to create a Redshift Physical Light, go to

its 『Area』 settings and set the 『Shape』 type to 『Mesh』.

在Maya中創建多邊形光源的方法是：在Area下的Shape中類型Mesh。

Then,in your scene, left-click select a mesh and then shift-select the light itself.

Then click the 「Link」 button on the light』s properties.然後在場景中左鍵選擇多邊形，再Shift增選這盞光源，然後點擊屬性中的Link按鈕。

Texturing紋理貼圖

Just like any area light in Redshift, mesh lights can be textured.

與Redshift中的其它區域光一樣，Mesh Lights可以使用紋理貼圖。

To texture a mesh light, you』ll need to ensure that the referenced mesh contains a

UV coordinate set.

要給Mesh Lights貼圖，首先要確保原始參考多邊形已經被正確展開了UV。

You can then texture your mesh light just like you』d texture any other area light:

by connecting a texture to the light』s 「Color」 parameter.

然後，就像其它區域光一樣，將貼圖與光源的Color屬性做連接即可。

Texturing a mesh light using a simple checkerboard pattern

使用簡單的棋盤格在多邊形光源上貼圖

Noise噪點

Typically, noise originating from a mesh light can be

reduced or eliminated by increasing the samples of the light itself. However,for mesh lights to be effective, GI has to also be enabled in the scene andmust be using enough samples. Similarly, if the mesh light can be seen throughlow-gloss reflections or refractions, then the reflection/refraction samples ofthe material itself might have to be increased.

通常，只要增加光源自身的採樣屬性（Samples），就可以降低甚至去除噪點。但是想要有效的使用多邊形光源，就應該在場景中打開GI，並設定足夠的採樣值。類似的，假如光源出現在高磨砂度物體的折射或者反射中，那麼需要提高這個物體相應折射或者反射的採樣值。

Please note that this is a special requirement for mesh lights and is not the casewith other light types!

請注意，只有Mesh Light才需要進行這種調整，其他光源類型不需要！

For non-mesh-lights, GI doesn』t have to be enabled and the number of samples of GI

or material reflection/refraction doesn』t affect the noise produced by the light!

對於非多邊形光源，GI不一定非要開啟。GI的採樣值或者折/反射的採樣值對不會對光源產生的噪點影響。

The images below show the type of artifacts that can be seen when GI is disabled.

下圖中可以看到，關閉GI之後，產生了瑕疵。

GI disabled. Even though the mesh light is using enough samples, there is still noise and some missing lighting around the hoofs

取消GI。儘管已經將採樣值設定得足夠大，但仍有噪點，而且馬蹄周圍缺乏光照。

With brute-force GI enabled, the artifacts around the hoofs are gone

開啟Brute-force GI，馬蹄周圍的問題消失了

Using Mesh Lights To Optimize Many-Light Situations

適合用Mesh Lights來優化燈光組情況

As shown above, if your scene contains many simple lights, you can use mesh lights to optimize your rendering times. Most renderers can render faster when there are fewer lights in the scene and Redshift is no exception!

像上面顯示的，假如場景包含許多簡單光源，就可以用Mesh Light來減少渲染時間。對於絕大多數情況，都是燈光越少渲染越快，Redshift也是如此。

Please note, though, that this type of trick can』t always be used. If the grouped lights are far away from each other or blocked from each other (because they are, say, in different rooms), then this kind of grouping can introduce significant noise!

請注意，這個技巧並不是總能奏效。假如燈光組的燈，相互距離很遠，或者之間被物體隔開（如比在不同的房間里），那麼這種單個Mesh Light替代燈光組的優化方法就可能產生明顯的噪點。

Ideally, you should try to group lights that are close to each other. Office lighting (i.e. a grid of overhead panels) or a grid of LED lights are the ideal situations for this type of optimization.

理想的情況是，將之間距離很近的簡單光源用一個Mesh Light組在一起。辦公室照明（比如一組頂光陣列）或者LED燈陣列最適合使用這種方法優化加速。

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