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This chapter lists all snap modes that can be activated to assist you to position the mouse cursor to an exact location.
For most constructions and modifications in QCad, it is necessary to specify the coordinates of reference points, startpoints, endpoints, centers or other identifying points. In order to make it possible to pick exact positions defined by previously drawn entities or by the grid, QCad offers a set of object snap modes. The toolbar that features those modes is shown in Figure 20. It is automatically shown whenever object snap modes can be used .
Figure
20: The object snap toolbar.
CAD Toolbar:
Menu:
Snap - Free
Hotkey:
os
Command:
free, fre
Description:
Allows the user to set the coordinate freely using the mouse. Note, that this is almost never the recommended way of setting coordinates in a CAD system.
CAD Toolbar:
Menu:
Snap - Grid
Hotkey:
sg
Command:
grid, gri
Description:
Snaps to grid points.
CAD Toolbar:
Menu:
Snap - Endpoints
Hotkey:
se
Command:
endpoint, end
Description:
Snaps to endpoints of lines and arcs and to points (Figure 21).
Figure
21: Endpoints found by the snap
tool.
CAD Toolbar:
Menu:
Snap - On Entity
Hotkey:
sn
Command:
near, nea
Description:
Snaps to the closest point that is on an entity (Figure 22).
Figure
22:'On Entity' snaps to any point
on the line of an entity.
CAD Toolbar:
Menu:
Snap - Centers
Hotkey:
so
Command:
center, cen
Description:
Snaps to centers of lines and arcs and to points (Figure 23).
Figure
23: Centers found by the snap
tool.
CAD Toolbar:
Menu:
Snap - Middle
Hotkey:
sm
Command:
middle, mid
Description:
Snaps to middle points of lines and arcs and to points (Figure 24). Note that the middle point of an arc is in the middle of the arc line while the center is at the center of the arc.
Figure
24: Middle points found by the snap
tool.
CAD Toolbar:
Menu:
Snap - Distance from Endpoint
Command:
distance, dist
Options Toolbar:
Description:
Snaps to points with a given distance from endpoints (Figure 25). The distance can be adjusted in the options toolbar.
Figure
25: Example snap points for the snap
tool 'Distance from Endpoint'.
CAD Toolbar:
Menu:
Snap - Intersection
Hotkey:
si
Command:
intersection, int
Description:
Snaps to intersections between entities (Figure 26).
Figure
26: The Intersection Snap tool finds
automatically all visible intersection points.
CAD Toolbar:
Menu:
Snap - Intersection Manually
Description:
Sometimes the intersection snap mode cannot be used to snap to an intersection point because the point is not on one or both of the entities. The second intersection tool lets you specify the two entities and then snaps the intersection point even if it is outside the entities (Figure 27).
Figure
27: The Manual Intersection Snap tool
also lets you specify invisible intersection points.
In addition to the snap functions described above, QCad can further
restrict the position of the mouse cursor orthogonally to the position of
the relative zero point. Figure
28 illustrates an example of how
to use snap restrictions.
The 'Snap Point' is the point the user wants to specify. It is the
point on the bottom line of the shape that has the same X-coordinate like
the center of the full circle.
The mouse cursor is located at the circle line. Because QCad is in
the snap mode "Snap to Center Points", the center of the circle would
normally be the snap point. A small rhombus highlights that point ("Center
Point"). With the snap restriction "Restrict Horizontally" activated, QCad
snaps to the point on the horizontal position of the relative zero point
("Snap Point").
Figure
28: Snap restrictions further
limit the snap position to imaginary lines orthogonally to the relative
zero point.
CAD Toolbar:
Menu:
Snap - Restrict Nothing
Description:
Disables all restrictions.
CAD Toolbar:
Menu:
Snap - Restrict Orthogonally
Description:
Restricts orthogonally to relative zero point.
CAD Toolbar:
Menu:
Snap - Restrict Horizontally
Description:
Restricts horizontally to relative zero point.
CAD Toolbar:
Menu:
Snap - Restrict Vertically
Description:
Restricts vertically to relative zero point.
As mentioned previously, there is a relative zero point in every QCad
drawing. It appears as a small red circle with a hair cross. The relative
zero point is the reference point for relative coordinates you enter in the
command line and for snapping restrictions.
Normally, the relative zero point moves around automatically. For
example if you are drawing a sequence of lines,
the relative zero point always moves to the last point you have just set.
The next point of the sequence can then be defined in coordinates relative
to that last point.
Sometimes this is not convenient and you would rather want to set the
relative zero point to another position or lock its position so it stops
moving around automatically. The snap toolbar offers two tools to do
this.
CAD Toolbar:
Menu:
Snap - Set Relative Zero
Command:
relativezero, relz
Description:
Lets you set a new location for the relative zero point.
CAD Toolbar:
Menu:
Snap - (Un-)Lock Relative Zero
Command:
lockrelativezero, lrel
Description:
When enabled, this switch locks the position of the relative zero point. This means it does not move around automatically. You can still move it manually using the tool described above.
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