标签：spec type ESS 大小 des span 图片 body sizeof
ifc方向提供二维或三维空间中的方向，具体取决于所提供的方向比率的数量。ifc方向并不意味着矢量长度，方向比也不必标准化。
注：定义根据ISO/CD 10303-42:1992
此实体定义二维或三维空间中的一般方向向量。分量的实际大小对定义的方向没有影响，只有X:Y:Z或X:Y的比值才有意义。
请注意，此实体的组件未规范化。如果需要单位矢量，则应在使用前对其进行规范化。
注：实体改编自ISO 10303-42中定义的方向。
IFC1.0中增加的新实体
Formal Propositions
| Rule | Description |
|---|---|
| MagnitudeGreaterZero | The magnitude of the direction vector shall be greater than zero. |
| # | Attribute | Type | Cardinality | Description | C |
|---|---|---|---|---|---|
| IfcRepresentationItem | |||||
| LayerAssignment | IfcPresentationLayerAssignment @AssignedItems |
S[0:1] | Assignment of the representation item to a single or multiple layer(s). The LayerAssignments can override a LayerAssignments of the IfcRepresentation it is used within the list of Items. | X | |
| StyledByItem | IfcStyledItem @Item |
S[0:1] | Reference to the IfcStyledItem that provides presentation information to the representation, e.g. a curve style, including colour and thickness to a geometric curve. | X | |
| IfcGeometricRepresentationItem | |||||
| IfcDirection | |||||
| 1 | DirectionRatios | IfcReal | L[2:3] | The components in the direction of X axis (DirectionRatios[1]), of Y axis (DirectionRatios[2]), and of Z axis (DirectionRatios[3]) | X |
| Dim :=HIINDEX(DirectionRatios) |
IfcDimensionCount | [1:1] | The space dimensionality of this class, defined by the number of real in the list of DirectionRatios. | X | |
ENTITY IfcDirection SUBTYPE OF (IfcGeometricRepresentationItem); DirectionRatios : LIST [2:3] OF IfcReal; DERIVE Dim : IfcDimensionCount := HIINDEX(DirectionRatios); WHERE MagnitudeGreaterZero : SIZEOF(QUERY(Tmp <* DirectionRatios | Tmp <> 0.0)) > 0; END_ENTITY;
标签：spec type ESS 大小 des span 图片 body sizeof
原文地址：https://www.cnblogs.com/herd/p/13299627.html
