Metallic mode: Metallic Parameter 金屬模式： 金屬參數
本文檔主要是對Unity官方手冊的個人理解與總結（其實以翻譯記錄爲主：>）
僅作爲個人學習使用，不得作爲商業用途，歡迎轉載，並請註明出處。
文章中涉及到的操作都是基於Unity2018.1版本
參考鏈接：https://docs.unity3d.com/Manual/StandardShaderMaterialParameterMetallic.html
When working in the Metallic workflow (as opposed to the Specular workflow), the the reflectivity and light response of the surface are modified by the Metallic level and the Smoothness level.
在金屬工作流程中(與高光工作流程相反)，表面的反射率和光照響應通過金屬層和平滑層進行調整。
Specular reflections are still generated when using this workflow but they arise naturally depending on the settings you give for the Metallic and Smoothness levels, rather than being explicitly defined.
使用這個工作流時仍然生成高光反射，但它們是自然產生的，取決於您爲金屬和平滑層所提供的設置，而不是顯式定義的。
Metallic mode is not just for materials which are supposed to look metallic! This mode is known as metallic because of the way you have control over how metallic or non-metallic a surface is.
金屬模式不僅僅適用於那些看起來像金屬的材料! 這種模式被稱爲金屬模式，因爲你可以控制一個表面是金屬的還是非金屬的。
Metallic parameter 金屬參數
The metallic parameter of a material determines how “metal-like” the surface is. When a surface is more metallic, it reflects the environment more and its albedo colour becomes less visible. At full metallic level, the surface colour is entirely driven by reflections from the environment. When a surface is less metallic, its albedo colour is more clear and any surface reflections are visible on top of the surface colour, rather than obscuring it.
材質的金屬參數決定了表面的“金屬性”程度。當一個表面越金屬化時，它會更多地反射環境，反照率顏色變得不那麼明顯。全金屬表面顏色完全由環境反射驅動。不那麼金屬化時，它的反照率顏色更清晰，任何表面反射的顏色上都是可見的，而不是模糊。
A range of metallic values from 0 to 1 (with smoothness at a constant 0.8 for all samples)
金屬值範圍從0到1(平滑度爲0.8，適用於所有樣品)
By default, with no texture assigned, the Metallic and Smoothness parameters are controlled by a slider each. This is enough for some materials. However if your model’s surface has areas with a mixture of surface types in the albedo texture, you can use a texture map to control how the metallic and smoothness levels vary across the surface of the material. For instance if your texture contains a character’s clothing including some metal buckles and zips. You would want the buckles and zips to have a higher metallic value than the fabric of the clothes. To achieve this, instead of using a single slider value, a texture map can be assigned which contains lighter pixel colours in the areas of the buckles and zips, and darker values for the fabric.
默認情況下，沒有賦值紋理，金屬和平滑度參數由滑塊控制。這對於某些材質來說已經足夠了。然而，如果你的模型表面在反照率紋理中有混合表面類型的區域，你可以使用紋理貼圖來控制材質表面的變化金屬和平滑度。例如，如果你的材質包含一個角色的衣服，包括一些金屬扣和拉鍊。你會希望鈕釦和拉鍊的金屬價值高於衣服的面料。爲了達到這個目的，我們不能只使用單一的滑動條值，我們可以賦值紋理貼圖，紋理貼圖在鈕釦和拉鍊的區域中包含更亮的像素顏色，在布料的區域中包含更暗的顏色。
With a texture assigned to the Metallic parameter, both the Metallic and Smoothness sliders will disappear. Instead, the Metallic levels for the material are controlled by the values in the Red channel of the texture, and the Smoothness levels for the material are controlled by the Alpha channel of the texture. (This means the Green and Blue channels are ignored). This means you have a single texture which can define areas as being rough or smooth, and metallic or non-metallic, which is very useful when working texture maps that cover many areas of a model with varying requirements - for example a single character texture map often includes multiple surface requirements - leather shoes, cloth clothes, skin for the hands and face and metal buckles.
賦值金屬參數紋理後，金屬滑塊將消失。代替，材質的金屬性由貼圖的紅色通道中的數值控制，材質的平滑度階由貼圖的Alpha通道控制。(這意味着忽略綠色和藍色通道)。這意味着你有一個單一的紋理，它可以定義區域是粗糙的還是光滑的，以及金屬的還是非金屬的，這在處理紋理映射時非常有用，紋理映射覆蓋了模型的許多區域，並且有不同的需求——例如，一個角色紋理圖通常包括多個表面需求-皮鞋，布料衣服，手和臉的皮膚和金屬鈕釦。
This image shows a case model with no metallic map
In the example above, the case has an albedo map, but no texture for Metallic. This means the whole object has a single metallic and smoothness value, which is not ideal. The leather straps, the metal buckles, the sticker and the handle should all appear to have different surface properties.
在上面的例子中，案例有一個反照率貼圖，但是沒有金屬貼圖。這意味着整個物體有一個單一的金屬性和平滑度值，這是不理想的。皮帶，金屬扣，貼紙和把手都應該有不同的表面屬性。
This image shows a case model with a metallic map applied
In this example, a Metal/Smoothness texture map has been assigned. The buckle now has a high metallic value and responds to light accordingly. The leather straps are shinier than the leather body of the box, however they have a low “Metallic” value, so it appears to be shiny non-metal surface. The black and white map on the far right shows the lighter areas for metal, and mid to low greys for the leather.
在這個例子中，一個金屬/平滑紋理貼圖已經被賦值。金屬扣現在有一個高的金屬值和相應的光照。皮帶比箱體的皮錶帶更光亮，但是“金屬”值較低，所以看起來是有光澤非金屬的表面。最右邊的黑白貼圖顯示了金屬的更亮區域，以及皮帶的中低灰色區域。