IfcSurfaceStyleRendering
IfcSurfaceStyleRendering保存与特定曲面侧样式相关的可视化特性。它允许通过以下方式定义渲染属性：
颜色组件（从IfcSurfaceStyleShading继承的SurfaceColor属性）
透明度组件（从IfcSurfaceStyleShading继承的透明度属性）
反射率分量，由
将反射系数应用于表面颜色：
漫反射组件（表面颜色*漫反射因子）
传输部件（表面颜色*传输系数）
漫反射透射组件（表面颜色*漫反射透射系数）
反射组件（表面颜色*反射因子）
镜面反射组件（SurfaceColor*镜面反射因子属性与镜面反射高光）
或者，通过明确定义颜色等因素（漫射颜色、透射颜色、漫射透射颜色、反射颜色和镜面颜色）
置换组件，当前仅由TextureType=凹凸的纹理贴图提供
覆盖率分量，目前仅由纹理贴图的alpha分量给出（2或4分量颜色纹理）
注：继承属性SurfaceColour被视为环境光颜色，并指定该表面应反射的光源环境光数量。环境光是全向的，只取决于光源的数量，而不是它们相对于表面的位置。
注：如果IfcReflectanceMethodEnum给出的反射法为“玻璃”，则透射系数控制玻璃中的透明度水平，在这种情况下，透明度系数被解释为透射系数。
注：如果包括透明度和透射率颜色（或系数），则以下定义适用：
透明度是2*PI sr（一个半球）立体角中透射通量的比率。这是一种简单的颜色过滤，不考虑折射。
材料的透射系数是给定立体角中的透射通量与在相同立体角中100%透射的完全漫反射材料的透射通量之比。它是穿过材料并可能被折射的光的一部分。
注意：有关反射方程式以及有关曲面样式特性及其处理的更多信息，请参见：
ISO/IEC 14772-1:1997：虚拟现实建模语言
IFC2x中增加的新实体。
Attribute inheritance
| # | Attribute | Type | Cardinality | Description | C |
|---|---|---|---|---|---|
| IfcPresentationItem | |||||
| IfcSurfaceStyleShading | |||||
| 1 | SurfaceColour | IfcColourRgb | [1:1] | The colour used to render the surface. The surface colour for visualisation is defined by specifying the intensity of red, green and blue. | X |
| 2 | Transparency | IfcNormalisedRatioMeasure | [0:1] | The transparency field specifies how "clear" an object is, with 1.0 being completely transparent, and 0.0 completely opaque. If not given, the value 0.0 (opaque) is assumed.
NOTE The definition of 1 being transparent and 0 being opaque is the opposite of the definition in alpha channels, where 0.0 is completely transparent and 1.0 is completely opaque. This definition is due to upward compatibility to previous versions of this standard in different to the definition in IfcIndexedColourMap. |
X |
| IfcSurfaceStyleRendering | |||||
| 3 | DiffuseColour | IfcColourOrFactor | [0:1] | The diffuse part of the reflectance equation can be given as either a colour or a scalar factor. The diffuse colour field reflects all light sources depending on the angle of the surface with respect to the light source. The more directly the surface faces the light, the more diffuse light reflects. The diffuse factor field specifies how much diffuse light from light sources this surface shall reflect. Diffuse light depends on the angle of the surface with respect to the light source. The more directly the surface faces the light, the more diffuse light reflects. The diffuse colour is then defined by surface colour * diffuse factor. | X |
| 4 | TransmissionColour | IfcColourOrFactor | [0:1] | The transmissive part of the reflectance equation can be given as either a colour or a scalar factor. It only applies to materials which Transparency field is greater than zero. The transmissive colour field specifies the colour that passes through a transparant material (like the colour that shines through a glass). The transmissive factor defines the transmissive part, the transmissive colour is then defined by surface colour * transmissive factor. | X |
| 5 | DiffuseTransmissionColour | IfcColourOrFactor | [0:1] | The diffuse transmission part of the reflectance equation can be given as either a colour or a scalar factor. It only applies to materials whose Transparency field is greater than zero. The diffuse transmission colour specifies how much diffuse light is reflected at the opposite side of the material surface. The diffuse transmission factor field specifies how much diffuse light from light sources this surface shall reflect on the opposite side of the material surface. The diffuse transmissive colour is then defined by surface colour * diffuse transmissive factor. | X |
| 6 | ReflectionColour | IfcColourOrFactor | [0:1] | The reflection (or mirror) part of the reflectance equation can be given as either a colour or a scalar factor. Applies to "glass" and "mirror" reflection models. The reflection colour specifies the contribution made by light from the mirror direction, i.e. light being reflected from the surface. The reflection factor specifies the amount of contribution made by light from the mirror direction. The reflection colour is then defined by surface colour * reflection factor. | X |
| 7 | SpecularColour | IfcColourOrFactor | [0:1] | The specular part of the reflectance equation can be given as either a colour or a scalar factor. The specular colour determine the specular highlights (e.g., the shiny spots on an apple). When the angle from the light to the surface is close to the angle from the surface to the viewer, the specular colour is added to the diffuse and ambient colour calculations. The specular factor defines the specular part, the specular colour is then defined by surface colour * specular factor. | X |
| 8 | SpecularHighlight | IfcSpecularHighlightSelect | [0:1] | The exponent or roughness part of the specular reflectance. | X |
| 9 | ReflectanceMethod | IfcReflectanceMethodEnum | [1:1] | Identifies the predefined types of reflectance method from which the method required may be set. | X |
EXPRESS Specification
ENTITY IfcSurfaceStyleRendering
SUBTYPE OF (IfcSurfaceStyleShading);
DiffuseColour : OPTIONAL IfcColourOrFactor;
TransmissionColour : OPTIONAL IfcColourOrFactor;
DiffuseTransmissionColour : OPTIONAL IfcColourOrFactor;
ReflectionColour : OPTIONAL IfcColourOrFactor;
SpecularColour : OPTIONAL IfcColourOrFactor;
SpecularHighlight : OPTIONAL IfcSpecularHighlightSelect;
ReflectanceMethod : IfcReflectanceMethodEnum;
END_ENTITY;
#######################################