原理化 BSDF

原理化 BSDF 将多层材质合而为一，形成单个简单易用的节点。它能够模拟多种多样的材质。

该着色器基于 OpenPBR 表面着色模型，并提供了与其它同类软件中类似的物理渲染（PBR）着色器兼容的参数设置，例如迪士尼（Disney）和标准表面（Standard Surface）。通过 Substance Painter 等软件绘制或烘焙生成的图像纹理，可直接连接到该着色器的对应输入接口。

层

基础层由金属（Metal）、漫反射（Diffuse）、次表面散射（Subsurface）和透射（Transmission）等部分混合构成。大多数材质会使用其中一种组件，但也可在它们之间实现平滑过渡混合。

金属成分（Metal）是不透明的，仅反射光线。漫反射（Diffuse）完全不透明，而次表面散射（Subsurface）则包含物体表面下方浅层的光线散射。漫反射与次表面散射部分均位于高光层（Specular Layer）下方。透射（Transmission）部分则同时包含反射与折射效果。

在所有基础层之上，还有可选添加的清漆涂层（glossy coat）。最后，光泽层（sheen layer）位于所有其他层之上，可用于添加绒毛或灰尘效果。

此外还可添加自发光效果（Light emission）。自发光的光线从清漆涂层（coat）和光泽层（sheen layers）下方发出，可用于模拟带有保护涂层或灰尘覆盖的自发光显示设备效果。

输入

基础色

材质的整体颜色，用于漫反射、次表面散射、金属和透射成分。

多种材质类型公用的基础色

粗糙度

指定表面的微观粗糙度，该参数控制镜面反射与透射。数值为 0.0 时会产生完全清晰的反射，而 1.0 时则会呈现漫反射效果。

从 0.0 到 1.0 的粗糙度变化过程

金属度

控制类塑料与类金属材质模型之间的混合过渡。当数值为 0.0 时，材质由具有漫反射或透射特性的基层构成，并在其上方叠加镜面反射层；当数值为 1.0 时，材质将呈现完全由基色着色的镜面反射效果，不含漫反射或透射成分。

从 0.0 到 1.0 的金属度变化过程

IOR

Index of refraction (IOR) for specular reflection and transmission. For most materials, the IOR is between 1.0 (vacuum and air) and 4.0 (germanium). The default value of 1.5 is a good approximation for glass.

IOR（折射率）从 1.0 到 2.0 的变化过程

Alpha

控制表面的透明度，数值设定为 1.0 时，表面完全不透明。通常连接到图像纹理着色器节点的 Alpha 输出接口。

从 0.0 到 1.0 的 Alpha 值变化过程

法向

控制基础图层的法线方向。

漫反射

糙度 仅限 Cycles

表面粗糙度；值为 0.0 时，给出标准的 Lambertian 反射，更高的值则激活 Oren-Nayar BSDF 。

次表面

Subsurface scattering is used to render materials such as skin, milk and wax. Light scatters below the surface to create a soft appearance.

方法

Rendering method to simulate Subsurface scattering.

克里斯坦森-伯利:

基于物理的体积散射的近似值。此方法不如 随机游走 准确，但是，在某些情况下，此方法将更快地解决噪声。

随机游走:

Cycles Only Provides accurate results for thin and curved objects. Random Walk uses true volumetric scattering inside the mesh, which means that it works best for closed meshes. Overlapping faces and holes in the mesh can cause problems.

随机游走(皮肤):

Cycles Only Random walk method optimized for skin rendering. The radius is automatically adjusted based on the color texture, and the subsurface entry direction uses a mix of diffuse and specular transmission with custom IOR. This tends to retain greater surface detail and color and matches measured skin more closely.

权重

漫反射表面和次表面散射之间的混合。通常应为 0 或 1（完全漫反射或次表面）。

权重位于 0.0 至 1.0 之间

半径

光散射到表面下方的平均距离。较高的半径可以使外观更柔和，因为光线会流入阴影区域并穿过物体。散射距离是针对RGB通道单独指定的，对于具有较强红光散射的面板材质，渲染效果较佳。X，Y和Z的数值会分别映射到R，G和B的值。

半径位于白色到红色之间

缩放

应用于半径的缩放值。

缩放位于 0 cm 至 50 cm 之间

IOR 仅限 Cycles

Index of refraction (IOR) used for rays that enter the subsurface component. This may be set to a different value than the global IOR to simulate different layers of skin.

IOR（折射率）从 1.0 到 2.0 的变化过程

各向异性 仅限 Cycles

次表面中体积散射的方向性。零为所有方向上均匀散射，值越高，向前散射越强烈。例如，皮肤已被测定为具有0.8的各向异性。

各向异性位于 0.0 至 1.0 之间

高光

Controls for both the metallic component and specular layer on top of diffuse and subsurface.

分布

要使用的微面分布。

GGX:

A method that is faster than Multiple-scattering GGX but is less physically accurate.

多重散射GGX:

Takes multiple scattering events between microfacets into account. This gives more energy conserving results, which would otherwise be visible as excessive darkening.

折射率等级

Adjustment to the IOR to increase or decrease intensity of the specular layer. 0.5 means no adjustment, 0 removes all reflections, 1 doubles them at normal incidence.

This input is designed for conveniently texturing the IOR and amount of specular reflection.

IOR 等级位于 0.0 到 1.0 之间

色调

Color tint for specular and metallic reflection.

For non-metallic tints provides artistic control over the color specular reflections at normal incidence, while grazing reflections remain white. In reality non-metallic specular reflection is fully white.

For metallic materials tints the edges to simulate complex IOR as found in materials such as gold or copper.

染色位于白色到黄色之间

各向异性 仅限 Cycles

镜面反射的各向异性量。较高的设定值可提供沿切线方向的细长高光；设定为负值则会给出垂直于切线方向的高光。

各向异性过滤位于 0.0 至 1.0 之间

各向异性旋转 仅限 Cycles

旋转各向异性的方向，取值 1.0 表示旋转一整圈。

Compared to the Glossy BSDF node, the direction of highlight elongation is rotated by 90°. Add 0.25 to the value to correct.

各向异性旋转位于 0.0 至 1.0 之间

切向 (正切)

控制各向异性的切向。

透射

Transmission is used to render materials like glass and liquids, where the surface both reflects light and transmits it into the interior of the object

权重

Mix between fully opaque surface at zero and fully transmissive at one.

权重位于 0.0 至 1.0 之间

涂层

Coat on top of the materials, to simulate for example a clearcoat, lacquer or car paint.

权重

Controls the intensity of the coat layer, both the reflection and the tinting. Typically should be zero or one for physically-based materials, but may be textured to vary the amount of coating across the surface.

权重位于 0.0 至 1.0 之间

粗糙度

涂层的粗糙度。

从 0.0 到 1.0 的粗糙度变化过程

IOR

Index of refraction (IOR) of the coat layer. Affects its reflectivity as well as the falloff of coat tinting.

IOR（折射率）从 1.0 到 2.0 的变化过程

色调

通过创建一个吸收层，给涂层添加一个带颜色的染色。随着光在介质中传播得更远（取决于涂层IOR），在较浅的角度饱和度增加。

染色位于白色到蓝色之间

法向

Controls the normals of the Coat layer, for example to add a smooth coating on a rough surface.

光泽

Sheen simulates very small fibers on the surface. For cloth this adds a soft velvet like reflection near edges. It can also be used to simulate dust on arbitrary materials.

权重

控制光泽层的强度。

权重位于 0.0 至 1.0 之间

粗糙度

边缘光泽的粗糙度。

从 0.0 到 1.0 的粗糙度变化过程

色调

边缘光泽的颜色。

染色位于白色到绿色之间。

自发光(发射)

来自表面的自发光。

颜色

表面自发光的颜色。

自发光颜色变化

强度

自发光的强度。取值 1 意为确保图像中的物体具有与 自发光颜色 完全相同的颜色，或者说使其“无明暗(shadeless)”。

强度位于 0.0 至 10.0 之间

薄膜 仅限 Cycles

Thin Film simulates the effect of interference in a thin film sitting on top of the material. This causes the specular reflection to be colored in a way which strongly depends on the view angle as well as the film thickness and the index of refraction (IOR) of the film and the material itself.

This effect is commonly seen on e.g. oil films, soap bubbles or glass coatings. While its influence is more obvious in specular highlights, it also affects transmission.

Note

Thin-film interference is currently only applied to dielectric materials. Support for thin films on top of Metallic is planned in the future.

厚(宽)度

The thickness of the film in nanometers. A value of 0 disables the simulation. The interference effect is strongest between roughly 100 and 1000 nanometers, since this is near the wavelengths of visible light.

IOR

Index of refraction (IOR) of the thin film. The common range for this value is between 1.0 (vacuum and air) and roughly 2.0, though some materials can reach higher values. The default value of 1.33 is a good approximation for water. Note that when the value is set to 1.0 or to the main IOR of the material, the thin film effect disappears since the film optically blends into the air or the material.

输出

BSDF

标准着色器输出。