Utility Shaders - Normal Map
General概述
Normal mapping is a texture-based technique used to give the impression of sub-polygon lighting detail, without having to model it. It is controlled by a 『normal』 texture, which is used to perturb the surface normal. Since only normals are perturbed, not geometry, it does not affect shadows.
法線貼圖是一個基於紋理貼圖的技術，無需建模就能展示子多邊形的光線細節。通過法線紋理擾亂表面的法線來控制法線貼圖，因只是法線被擾亂，而不是真產生幾何體，所以陰影不受影響。
The resolution of the normal map texture is important – you ideally want a one pixel per texel maximum resolution to get the best visual results. Magnifying the texture will blur the results and minifying will lessen the effect with distance.
The output of this shader is a perturbed normal.
法線貼圖紋理的解析度是很重要的-------理想的情況下紋理的解析度要滿足最大特寫時，一個渲染像素佔一個紋理像素，這樣才能獲得最好的效果。紋理被放大時會產生模糊，相反被縮小或者放在遠處時就不會有大問題。
Shader Options著色器選項
General概述
This controls the basic properties of the normal map.
選項控制法線貼圖基本屬性
Texture紋理
Map貼圖
This is the texture map that contains the normals.
法線的紋理貼圖
Texture Space紋理空間
This is the texture mapping space, which defines the uv channel.
定義了UV通道的紋理貼圖空間。
Unbiased Normals無偏法線
8-bit integer texture maps normally store values between 0.0 and 1.0, but normals
have component values between -1.0 and 1.0. When this is the case, the normals will have been pre-biased to fit into the 0.0 to 1.0 range. Check this option only when you know that the texture map is unbiased, meaning the normals were floating point and stored in the -1.0 to 1.0 range.8位整數的紋理映射通常存儲在0.0和1.0之間，但法線分量值在-1.0和1.0之間。在這種情況下，法線將被預先偏移到0.0到1.0的範圍內。只有在已知紋理貼圖是無偏模式下時才需要勾選。也就是說，法線是以浮點數存儲在-1.0到1.0之間的。
Flip Normal Y翻轉Y軸
This allows you to flip the y of the normal map, which is useful if the normal map
was generated using a flipped uv coordinate system.允許你沿Y軸翻轉法線貼圖，如果法線貼圖是使用的UV坐標系統被翻轉過，那麼可以使用這個選項。
Scale Normal縮放法線
This allows you to scale the resultant normal from the normal map, yielding a stronger 『bump』 effect.
允許縮放法線貼圖中的合成法線偏移量，產生更強的凹凸效應。
Tangents切線
Tangents切線
This is the channel for the pre-computed surface tangents, since normal mapping is always calculated in tangent space.
預計算表面節線的通道。因為法線貼圖是以切線空間計算的。
Advanced高級
This gives you extra options for filtering and defined the texture coordinates. For examples, see 『Image Sampler』 document.
提供過濾和定義紋理坐標的額外選項。有關實例，請參見Image Sampler文檔。
Elliptical Filtering橢圓形過濾
Enable開啟
This enables elliptical filtering, which yields the best quality for texture sampling at shallow angles. When this is not checked, bi-linear filtering will be used.
啟用橢圓形過濾可在淺角度得到最好質量的紋理採樣。不勾選這個選項時，將使用雙線生過濾。
Maximum Eccentricity最大偏心率
This specifies the maximum eccentricity for elliptical filtering. The higher the value the better the results, but at the cost of performance. A value of 1.0 is the same as bi-linear filtering.
指定橢圓形過濾的最大離心率。數值越大效果越好，但是以性能作為代價。A數值為1.0的時等同於使用雙線性過濾。
Alternate可選
U / V
This specifies whether alternate texture coordinate repetition should be reversed.
確定是否應該反轉UV紋理坐標。
Repeats重複
Texture Repeats紋理重複
This controls the repetition of the texture coordinates. Normally a texture is mapped with values 0.0 to 1.0, to cover the whole texture. A 『Texture Repeat』 value of 2.0, for example, means that the whole texture will fit twice in the same 0.0 to 1.0 range. Values lower than 1.0 effectively act as magnification.
控制紋理坐標的重複。通常要覆蓋整個紋理， 一個紋理映射值在0.0到1.0之間。比如Texture
Repeat的值為2.0時，意味著整個紋理在0.0到1.0之間重複2次。數值小於1.0會放大紋理。Wrap U/V包裹
This enables U/V wrapping when the values are out of the 0.0 – 1.0 range.
數值不在0.0到1.0範圍內時，啟動UV包裹。
This option is only available in Maya. Softimage does not need this.
這個選項僅Maya 可用，Softimage不需要。
UV Remap UV沖貼圖
Minimum / Maximum最小/最大
This specifies the range in which the texture coordinates will be remapped to.
指定紋理坐標重新映射的範圍。
Normal Map Example
Here is an example of how a normal map can enhance the lighting detail of simple, flat geometry.
此處舉例說明一個Normal Map如何能提高簡單的平面幾何的燈光細節。
The following simple example shows an un-textured surface, with a diffuse and glossy reflected spherical area light.以下是個簡單的例子，物體表面沒有紋理貼圖，區域光源對Diffuse和Glossy Reflected起作用。
The example below noew shows how a normal map can dramatically increase the lighting detail, without paying for the extra polygons.下面的例子顯示了法線貼圖如何顯著地提高燈光細節，且無須為這些多出的細節付出任何渲染成本。
The image below shows the normal map that was used to create the effect.下圖顯示了用來達成效果的法線貼圖。
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