Draft Snap/zh-cn

描述
在底图工作台工具中，您可以通过指针单击3D视图来拾取图形中的点、距离、半径与角度.

但是，当这些参数需要特别精准时，可能就要在工具对话框中输入准确的底图坐标.

选择更加精确点的另一种方式是借助捕捉（snapping）功能. 所谓捕捉，意即将您设置的下一个点“黏”在某个已存在的点或另一对象的某部分上.

捕捉功能可用于底图工作台与建筑工作台（Arch Workbench）中的大多工具，利用捕捉工具栏中的按钮即可对此功能进行全局开启或关闭. 而通过菜单便可以激活捕捉工具栏. 通过点选捕捉工具栏中的各按钮，即可开启或关闭对应的捕捉方法.

同时采用多种捕捉方法，可能会便于您将对象绘制在预期位置上. 但如果您的鼠标指针频繁被导向在一个错误的点上，那也许就是采用多种捕捉方法所带来的副作用，此时，请尝试仅采用一种捕捉方法.



Available snap locations

 * [[Image:Snap_Near.svg|32px]] Near: snaps to the closest point or edge on the nearest object.
 * [[Image:Snap_Extension.svg|32px]] Extension: snaps on an imaginary line that extends beyond the endpoints of line segments. Hover the mouse over the desired object to activate its extension snap.
 * [[Image:Snap_Parallel.svg|32px]] Parallel: snaps on an imaginary line parallel to a line segment. Hover the mouse over the desired object to activate its parallel snap.
 * [[Image:Snap_Grid.svg|32px]] Grid: snaps to the intersections of the grid lines, if the grid is visible.
 * [[Image:Snap_Endpoint.svg|32px]] Endpoint: snaps to the endpoints of line, arc and spline segments.
 * [[Image:Snap_Midpoint.svg|32px]] Midpoint: snaps to the middle point of line and arc segments.
 * [[Image:Snap_Perpendicular.svg|32px]] Perpendicular: on line and arc segments, snaps perpendicularly to the latest point.
 * [[Image:Snap_Angle.svg|32px]] Angle: snaps to the special cardinal points of circles and arcs, at 45° and 90°.
 * [[Image:Snap_Center.svg|32px]] Center: snaps to the center point of arcs and circles.
 * [[Image:Snap_Ortho.svg|32px]] Ortho: snaps on imaginary lines that cross the last point, and extend at 0°, 45° and 90°.
 * [[Image:Snap_Intersection.svg|32px]] Intersection: snaps to the intersection of two line or arc segments. Hover the mouse over the two desired objects to activate their intersection snaps.
 * [[Image:Snap_Special.svg|32px]] Special: snaps on special points defined by the object.
 * [[Image:Snap_Dimensions.svg|32px]] Dimensions: shows temporary X and Y dimensions while snapping.
 * [[Image:Snap_WorkingPlane.svg|32px]] Working plane: always places the snapped point on the current working plane, even if you snap to a point outside that working plane.

Advanced snapping

 * Additional snap locations can be obtained by combining two snapping methods, such as Draft Ortho and Draft Extension, that will give you a snap point at the intersection of their imaginary lines.
 * Other snap locations can be obtained by using Draft Constrains, that is, by holding or pressing,  or  while drawing.
 * Press while drawing to insert a "hold point" at the current location of the cursor. You will then be able to snap orthogonally to these hold points, and at the intersections of their orthogonal axes. If Draft Midpoint snapping is enabled, you will also be able to snap at the mid distance between any two hold points.

Options

 * [[Image:Draft_ToggleGrid.svg|32px]] Toggle grid: turns the working plane grid on and off.
 * [[Image:Snap_Lock.svg|32px]] Lock: turns snapping on and off globally.
 * The maximum distance at which a point is considered a snapping point is specified in the Draft Preferences, and can also be changed on-the-fly by pressing (increase) or  (decrease) keys.
 * Pressing while drawing locks the current angle of the line segment being drawn.