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The SEDRIS Data Representation Model
APPENDIX A - Classes Face Direction |
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An instance of this DRM class specifies which side (the front or the back) of the given topological face is associated with the given <Areal Feature> instance.
Consider an <Areal Feature> instance representing a grass-covered region, consisting of a single <Feature Face> instance. The <Face Direction> link data on the relationship between them is set to SE_TRUE, indicating that the front (that is, the top) side of the face corresponds to the <Areal Feature> instance.
In such a case the <Feature Face> would appear twice in the collection of <Feature Face> components of the <Areal Feature>, once with the <Face Direction> set to SE_TRUE (front), and once with the <Face Direction> set to SE_FALSE (back).
In such a case the <Feature Face> would appear once in the collection of <Feature Face> components of each of the two <Areal Features>. For the <Areal Feature> corresponding to the front side of the face, the <Face Direction> would be set to SE_TRUE, while for the <Areal Feature> corresponding to the back side of the <Feature Face>, the <Face Direction> would be set to SE_FALSE.
At feature topology levels 0 through 3, <Face Direction> shall always be SE_TRUE (front). Only at feature topology level 4 can the back side of a <Feature Face> be associated with an <Areal Feature>.
| SE_Boolean | front; | (notes) |
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The <A CLASS="Face_Direction#front">front</A> field specifies whether the front side of the given face instance is that associated with the given SEDRIS object.
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