草图工作台中的根据中点创建椭圆工具

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Sketcher Create Ellipse by center

Menu location
Sketch → Sketcher geometries → Create ellipse by center
Workbenches
Sketcher
Default shortcut
None
Introduced in version
0.15
See also
Sketcher Ellipse by 3 Points, Sketcher Circle, Sketcher Arc of Ellipse

描述

本工具会根据用户拾取的三个点:中点、长半轴点与短半轴点来绘制一个椭圆。 在开启此工具时,鼠标指针会变为一个附有红色椭圆图标的白色十字。同时还会将当前的指针坐标实时显现在侧。

绘制椭圆所选中的一系列点以带数字的黄色箭头表示。C为中点,a - 长轴,b - 短轴,F1、F2为焦点。

如何使用

  • 通过点击工具按钮,选择对应菜单项或借助键盘快捷键(首先需要在Interface Customization中为之分配快捷键)来调用对应绘制椭圆命令。
  • 在3D视图中第一次点击所设置的是椭圆的中心。第二次点击所设置的是椭圆的第一个半径及其方向。第三次点击所设置的是另一种半径(前两次点击所定义的直线至第三次点击位置的距离即为第二个半径)。
  • 第三次点击后,椭圆就创建好了,与之共存的还有一系列对齐于它的构造几何对象(长轴、短轴、两个焦点)如果不需要这些构造几何对象,可将其手动删除,以后还可以重新创建。参见内部对齐约束在草图工作台中显示隐藏的内部几何图形
  • ESC键或单击鼠标右键来退出此功能。

Peculiarities

  • Major and minor axes of ellipses are strict and cannot be swapped by resizing the ellipse. This is a consequence of the solver parametrization used (center (x,y), focus1 (x,y) and minor radius length (b)) and the same strict behavior of OpenCascade. The ellipse must be rotated to swap the axes.
  • Ellipse can function as a circle when its major and minor diameter lines are deleted, and one of the foci is constrained to coincide with the center. But radius constraint won't work on such a circle.
  • Moving the ellipse by edge is the same as moving ellipse's center.