General概述

This shader simulates the scattering effect of skin. In real life, skin is made up of three distinct layers:

這個著色器模擬皮膚的散射效果。 在現實生活中，皮膚由三個不同的層組成：

• epidermis - defines the skin tone and waterproof layer
• 表皮 - 定義膚色和防水層

• dermis - contains tough connective tissue
• 真皮 - 含有堅韌的結締組織

• subcutis (hypodermis) - made up of loose connectivetissue, fat and blood vessels
• 皮下組織（皮下組織） - 由鬆散的結締組織，脂肪和血管組成

To model this, the Redshift skin shader has three

equivalent translucent, sub-surface scattering layers:

為了對此進行建模，Redshift的皮膚著色器有三個等效的半透明，子表面散射層：

• Shallow Scatter - defines the pigment/skin tone of the skin淺散射 - 定義皮膚的色素/膚色
• Mid Scatter - defines the dermis layer中間散射 - 定義真皮層
• Deep Scatter - defines the thick, subcutis layer深度散射 - 定義厚，皮下組織層

Redshift also simulates the 『waterproof』 oily property of the top-most epidermis layer by having a 『Primary Reflection』 control. A 『Secondary Reflection』 layer is also available for added sheen from, for example, oily cosmetic products, or for clear-coat effects.

Redshift還通過「主反射」控制模擬最頂層表皮層的「防水」油性特性。 「次級反射」層也可用於從例如油性化妝品添加的光澤，或用於透明塗層效果。

Note that as with all Redshift materials, the reflection layers are energy conserving, meaning with stronger reflection color and weights, the underlying diffuse scattering contribution will appear weaker.

注意，與所有Redshift材料一樣，反射層維持能量守恆原則，意味著具有更強的反射顏色和權重，基本的漫散射貢獻將看起來更弱。

Head model, courtesy of Lee Perry Smith, with a textured skin shader material, illuminated by two quad lights (one in front and one behind). You can see how sub-surface scattering of light affects thin parts of the model (the ear) versus the thick part of the model (the head).

頭部模型，由李佩裏史密斯提供，與紋理的皮膚著色材料，由兩個四燈（一個在前面和一個後面）照亮。 您可以看到光的子表面散射如何影響模型（耳朵）的薄部分與模型（頭部）的厚部分。

Scattering Layers散射層

The Shallow Scatter layer is the thinnest, so it should have the smallest Radius, yielding an almost diffuse scattering response. The Deep Scatter layer is the thickest layer, so it should have the largest radius, adding the blood tone under the skin.

淺散射層是最薄的，因此它應該具有最小的半徑，產生幾乎是漫散射的響應。 深層散射層是最厚的層，因此它應該具有最大的半徑，在皮膚下增加血色。

Each layer uses sub-surface scattering to compute a diffuse lighting result and the results are blended together based on each layer』s individual weight. For physically correct results, the sum of the layers should not exceed 1.0 (see the 『Normalize Diffuse Weights』 parameter). For more information about sub-surface scattering in general you can refer to the documentation on our sub-surface scattering material

shader.

每個層使用子表面散射來計算漫射照明結果，並且基於每個層的單獨重量將結果混合在一起。

對於物理正確的結果，層的總和不應超過1.0（請參閱「Normalize漫射權重」參數）。 有關子表面散射的更多信息，一般可以參考我們的子表面散射材料著色器的文檔。

Note that by setting the weights of the Mid and Deep Scatter layers to 0.0, this

shader can be used as an alternative to the regular sub-surface scattering material shader.

注意，通過將中間和深度散射層的權重設置為0.0，該著色器可以用作常規子表面散射材質著色器的替代。

Common常見屬性

Radius Scale半徑大小

Allows you to adjust the strength of the scattering effect for all the layers. Lower

values means scattered light is absorbed quicker, yielding a more diffuse look. Conversely, higher values yield a more translucent look.

允許您調整所有圖層的散射效果的強度。 較低的值意味著散射光被更快地吸收，產生更漫反射的外觀。

The sub-surface scattering effect is heavily dependent on object scale. Use this parameter to quickly tune the effect based on object scale until it is visually pleasing.

相反，更高的值產生更半透明的外觀。子表面散射效應嚴重依賴於對象尺度。 使用此參數可根據對象縮放快速調整效果，直到視覺效果令人滿意。

Overall Scale整體大小

Allows you to adjust the overall brightness of all the scattering layers.

允許您調整所有散射層的總體亮度。

Diffuse Amount 漫射量

Controls how much of the SSS effect you get. A value of 0.0 means that you』ll only get subsurface scattering. On the other hand, a value of 1.0 will make this surface behave as a perfectly diffuse surface without any SSS. This parameter is useful for materials that need a weaker SSS effect.

控制你獲得多少SSS效果。 值為0.0意味著你只能得到子表面散射。 另一方面，值為1.0將使得該表面表現為沒有任何SSS的完全漫射表面。 此參數對需要較弱SSS效應的材料有用。

Disable Diffuse Bump Mapping 禁用Diffuse Bump映射

This option allows you to switch to using the default un-bumped surface normals

for diffuse lighting calculations.

此選項允許您切換到使用默認的未碰撞曲面法線進行漫射照明計算。

Normalize Diffuse Weights 標準散射權重

In order to be physically correct, by default Redshift shaders conserve energy by not

emitting more light than they receive. When this parameter is checked, we apply physical correctness by ensuring the sum of the weights of each layer do not exceed 1.0.

為了物理上正確，默認情況下Redshift著色器通過不發射比它們接收的更多的光來維持能昨守恆。 當檢查該參數時，我們通過確保每個層的權重的和不超過1.0來確保物理正確性。

When this option is un-checked we leave the weights alone, which can result in

brighter, but not physically correct results.

當取消選中此選項時，我們只保留權重，這可能會導致更亮，但物理上不正確的結果。

Shallow / Mid / Deep Scatter Layers淺/中/深散射層

Color顏色

This is the color of the scatter.

這是散射層的顏色

Weight 權重

This is a multiplier of the scatter layer color and can be used to adjust the

brightness of the layer.

這是散射層顏色的乘數，可用於調整圖層的亮度。

This value is multiplied by the 『Overall Scale』 parameter.

此值乘以「Overall Scale」參數。

Radius半徑

This parameter is scene-scale related. It controls how deep light can travel within this surface. If the value is high, light can go deeper which creates a softer effect. Smaller values, on the other hand, mean that the light reaches extinction early which creates a harder effect.

此參數與場景相關。 它控制光在該表面內的行進深度。 如果該值高，光可以更深，這產生更柔和的效果。 另一方面，較小的值意味著光線較早達到消光，這產生了更強的效果。

This value is multiplied by the 『Radius Scale』 parameter.

此值乘以「Radius Scale半徑大小」參數。

The Overall Scale allows you to adjust the brightness of all the layers together, so you can quickly fine tune the intensity your diffuse lighting for the overall material.

「Overall Scale」允許您將所有圖層的亮度調整在一起，因此您可以快速微調整個材質的漫射照明的強度。

Note that the 『Overall Scale』 is applied prior to any layer weight normalization

(see 『Normalize Diffuse Weights』). This means if your layer weights sum to a value greater than 1.0, you may need lower 『Overall Scale』 values than expected in order to see a difference.

注意，「Overall Scale」在任何層重量歸一化之前應用（參見「Normalize Diffuse Weights」）。 這意味著如果您的圖層權重總和為大於1.0的值，您可能需要比預期更低的「Overall Scale」值才能看到差異

For physical correctness, the 『Normalize Diffuse Weights』 should be left enabled. This will ensure the material does not reflect more light than it receives. However, if you want better control over the overall layers brightness or want your material to be more emissive than physically correct, you can disable this option.

對於物理正確性，應該保持啟用「Normalize Diffuse Weights」。 這將確保材質不反射比它接收更多的光。 但是，如果您想要更好地控制整體層亮度，或者希望您的素材比物理上更正確，則可以禁用此選項。

Below is a side-by-side example showing the difference in lighting with the 『Normalize』 option disabled, using the default layer weights of the material.

下面是一個並排示例，顯示使用材質的默認層重量禁用「Normalize」選項時光線差異。

The 『Diffuse Amount』 lets you control how much of the overall sub-surface scatter effect you want, versus pure diffuse lighting. When the『Diffuse Amount』 is set to 1.0, there will be no sub-surface scattering. Equally, when set to 0.0, there will be only sub-surface scattering.

「Diffuse Amount」允許您控制您想要的總體子表面散射效果的多少，而不是純漫射照明。 當「Diffuse Amount」設置為1.0時，將沒有子表面散射。 同樣，當設置為0.0時，將只有子表面散射。

Now let』s take a look at how each layer can contribute to the scattering effect. While the differences can be subtle in this example, they are noticeable.

現在讓我們來看看每個層如何有助於散射效果。 雖然在這個例子中差異可以是微妙的，但是它們是顯而易見的。

Reflections反射

Primary / Secondary Reflection 主反射/次級反射

Color顏色

This defines the color of the reflection.

定義反射的顏色

Weight權重

This scales the overall amount of the reflection.

這縮放了反射的總量。

BRDF

New to 2.0 Feature 新2.0功能

This allows you to choose the technique for simulating physically correct rough

reflections. Beckmann is generally considered the standard for a good range of materials, but GGX has a wide specular tail, which is good for chrome materials.

這允許您選擇用於模擬物理正確的粗糙反射的技術。Beckmann通常被認為是各種材料的標準，但GGX有一個動態高光，這對鉻材料是有好處的。

Ashikhmin-Shirley(legacy)

Beckmann(Cook-Torrance)

GGX

Ashikhmin-Shirley

The legacy BRDF option uses a non-linear looking glossiness fall-off and exists to maintain compatibility with 1.0 materials.

傳統的BRDF選項使用非線性看起來光澤度下降，並且存在以保持與1.0材料的兼容性。

Glossiness光澤度

This controls the glossiness, or roughness, of the reflection. A glossiness of 1 means almost mirror reflection, while a glossiness of 0 means very rough,almost diffuse reflection.

這控制反射的光澤度或粗糙度。 光澤度1表示幾乎鏡面反射，而光澤度0表示非常粗糙，幾乎是漫反射。

Samples採樣

This defines the number of samples to use for the reflection. More samples means

less noise.

這定義了用於反射的樣本數。 更多的樣品意味著更少的噪點。

IOR

The index of refraction which is used to compute the view-dependent Fresnel

reflectivity effect. Reflections with an IOR value closer to 1.0 will have less facing reflectivity. The recommended default value is 1.44.

用於計算視圖相關菲涅耳反射率效應的折射率。 IOR值接近1.0的反射將具有較小的面對反射率。 建議的默認值為1.44。

General一般

Disable Reflection Bump Mapping禁用反射凹凸映射

This option allows you to switch to using the default un-bumped surface normals for direct and indirect reflection rays.

此選項允許您切換到使用默認的未碰撞表面法線的直接和間接反射光線。

Optimization優化

Specular Highlights Only僅限反射高光

This optimization option will disable indirect reflection ray tracing of the

environment and just capture specular reflections of lights.

此優化選項將禁用環境的間接反射光線跟蹤，並僅捕獲燈的鏡面反射。

Enable Trace Depth Override啟用跟蹤深度覆蓋

This enables the Max Reflection Trace Depth parameter.

這將啟用最大反射跟蹤深度參數。

When not enabled, the global trace depth will be used.

未啟用時，將使用全局跟蹤深度。

Note that when enabled, the override cannot exceed the global trace depth.

請注意，啟用時，覆蓋不能超過全局跟蹤深度。

Max Trace Depth最大跟蹤深度

This parameter controls the trace depth for reflection rays shot from this material. If the reflections of a material are not very defined (meaning: they are blurry because of the glossiness parameter or have a low weight), then multiple reflection bounces can be a waste of rendering time. This parameter allows the user to reduce the trace depth and speed up rendering.

此參數控制從此材料射出的反射光線的軌跡深度。 如果材料的反射不是非常定義的（意味著：它們由於光澤度參數而模糊或具有低重量），則多次反射反彈可能是浪費渲染時間。 此參數允許用戶減少跟蹤深度和加速渲染。

Cut-off Override Enable啟用截止覆蓋

This parameter allows you to override the global cut-off setting for reflections.

此參數允許您覆蓋反射的全局截止設置。

Cut-off Override Threshold截止覆蓋閾值

When the reflections of a material are very dark (because of low 「Weight」 or 「Color」values) they contribute very little to the final image. This parameter defines what is considered 「very dark」 at which point no more reflection rays will be shot - which will speed up rendering. Scenes containing very strong lights might need this parameter set to very low values such as 0.0001 in order to avoid early termination of tracing which can produce a grain-like effect.

當材料的反射非常暗（因為低「權重」或「顏色」值）時，它們對最終圖像貢獻很小。 這個參數定義什麼是「非常暗」，在這一點沒有更多的反射光線將被拍攝 - 這將加快渲染。 包含非常強的光的場景可能需要將該參數設置為非常低的值，例如0.0001，以避免可能產生顆粒樣效應的跟蹤的提前終止。

Bump Mapping凹凸貼圖

Add Bump Input To Material Bump

This is a legacy option for Maya and Softimage, which can have a bump mapping nodes connected straight to the material. When this parameter is enabled, any bump mapping node results connected to this shader will also be added to the bump mapping results of the material.

這是Maya和Softimage的傳統選項，可以使用直接連接到材質的凹凸貼圖節點。 啟用此參數時，連接到此著色器的任何凹凸貼圖節點結果也將添加到材質的凹凸貼圖結果。

Below are some examples of how different reflection settings can affect the look of the material.

下面是一些例子，說明不同的反射設置如何影響材料的外觀。

Texturing The Scattering Layers and Reflections紋理化散射層和反射

There are various tutorials on the web for different renderers that describe how to use texture maps for the sub-surface scattering layers. The tutorials that describe how to map three sub-surface layers also apply reasonably well to the Redshift skin material.

在網路上有不同的渲染器的各種教程，描述如何使用紋理貼圖的子表面散射層。 描述如何映射三個子表面層的教程同樣適用於Redshift表面材質。

Although the best results can be gotten using dedicated textures for the layers and reflections, here we show a simplified example, using a single diffuse texture that can be manipulated to add color detail to the shader, while still maintaining the sub-surface effect.

雖然最好的結果可以使用專門的紋理為圖層和反射，這裡我們展示一個簡化的例子，使用單個漫反射紋理，可以操縱添加顏色細節到著色器，同時仍然保持子表面效果。

The first step is to de-saturate the texture, then adjust its contrast to darken the dark details (such as facial hair). Once you have that texture you apply a red tint for the deep scatter color, a green-ish tint for the mid scatter color (so the sum of which becomes a deep orange) and simply use the diffuse texture for the shallow scatter layer. You can also use the de-saturated texture for the reflection color.

第一步是使紋理去除飽和度，然後調整其對比度以使黑暗細節（例如面部毛髮）變暗。 一旦你有了這種紋理，你可以為深散射顏色應用紅色的色調，為中散射顏色應用綠色的色調（所以它的總和變成深橙色），只需使用漫反射紋理作為淺散射圖層。 您還可以使用反飽和紋理作為反射顏色。

Below is an example showing the different layers, with its appropriate weight, and the other layers having a weight of 0.0.

下面是一個例子，顯示不同的層，其適當的權重，和其他層的權重為0。

Below now shows the layers successively summed together, by setting the layer weights to their appropriate values.

下面顯示了層與層累加的圖層，將圖層權重設置為適當的值。

Below is the equivalent Maya material shader graph

下面是Maya材質連接圖

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