消失的元素 non-existant in destination collection
The special geometric restrictions like parallelism and perpendicularity implicated in vanishing elements are deeply studied. In single-view case,the theory is presented to interpret relationship between two planar lines by applying 3D invariants of vanishing points.
详细论述了消失元素(消失点、消失直线、消失平面等)所体现的垂直、平行等特殊几何约束关系；对单视图，提出了一种利用消失点列的3D不变量解释平面直线关系的方法；对双视图，提出了利用自共轭三角形和对极几何约束，提取任意直线的消失点的算法，并在此基础了提出了一种利用消失元素的3D不变量解释直线间、直线与平面间、平面间等多种空间几何关系的方法。
参考来源 - 目标3D不变特征的提取与应用·2,447,543篇论文数据，部分数据来源于NoteExpress
注意当光标在元素上移动时工具提示是如何出现和消失的。
Notice how the tooltips appear and disappear as you move your cursor over the elements.
使用消失点来配置各平面的位置，可以让我能够顺着平面变化的趋势来增加元素。
With this setup in position I was now able to add elements that will be flowing along these planes.
另外，根元素的名称消失了。
Also you notice that the name of the root element has disappeared.
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