Object snap This chapter lists all object snap modes that can be activated to assist you in positioning reference points and determining coordinates.
For most design and machining steps in QCad, it is necessary to determine coordinates of reference points, start points, end points, centers, or other important points. In order to determine exact positions defined by existing objects, there are the object snap functions. The toolbar automatically displays these functions when they can be used (Figure 19).
Figure 19: The Object Snap Toolbar.
14.1. Free positioning
CAD Toolbar:
Allows free positioning with the mouse. Note that this is almost never the correct way to determine coordinates in a CAD system.
14.2. Catch grid points
CAD Toolbar:
Catches grid points.
14.3. End points catch
CAD toolbar:
Captures endpoints of lines, arcs, and points. (Figure 20).
Figure 20: Endpoints that can be caught with this tool.
14.4. Catch points on objects
CAD toolbar:
Catches the next point on an object (Figure 21).
Figure 21: On object' snaps to any point on the nearest object.
14.5. Snap centers
CAD toolbar:
Figure 22: Centers that can be snapped with this tool.
14.6. Snap center points
CAD toolbar:
Snap centers of lines, arcs and circles (Figure 23). Note that the center of an arc is at the center of the circle line on the arc.
Figure 23: Center points caught by this tool.
14.7. Points with distance to the end point
CAD toolbar:
Options toolbar:
Snap points with a specified distance to the nearest endpoint (Figure 24). The distance can be adjusted in the Options toolbar.
Figure 24: Points that can be snapped with this tool.
14.8. Intersection points
CAD toolbar:
Keyboard shortcut:
Snaps intersections between two objects (Figure 25).
Figure 25: This tool automatically snaps to the nearest (visible) intersection point.
14.9. Intersections (manual)
CAD toolbar:
Sometimes the above described tool for snapping intersection points does not work because the desired intersection point is not on one or both objects but outside of it. The second tool allows the two objects involved to be specified before the intersection point is snapped. This way invisible intersection points outside objects can be snapped as well. (Figure 26).
Figure 26: This tool can also be used to snap intersection points outside objects.
14.10. Snap constraints
In addition to the snap functions described above, QCad can further constrain the position of the snapped coordinate. The snapped point is then moved to the closest point orthogonal to the position of the absolute or relative zero point. Figure 27 shows an example of how snap constraints can be used. The 'snap point' is the point you want to determine. In the example, this is the point on the bottom line of the figure that has the same X-position as the center of the full circle. The mouse pointer is close to the circle line in the example. Because QCad is in snap mode "snap centers" normally the center of the circle would be the coordinate to be determined. A small rhombus highlights this point ("center"). With the snap constraint "Constrain horizontally" Instead, QCad snaps to the point that is horizontal to the relative zero point ("snap point").
Figure 27: Snap constraints further restrict the snapped position to imaginary lines orthogonal to the relative origin.
No constraint
CAD toolbar:
Turns off all constraints.
Orthogonal constraint
CAD toolbar:
Constrain orthogonal to the relative zero point.
Constrain horizontally
CAD toolbar:
Constrain horizontally to relative origin.
Constrain vertically
CAD toolbar:
Constrain Vertical to Relative Origin Point.
14.11. Relative zero point
As already mentioned, there is a relative zero point in every QCad drawing. This is displayed as a small red circle with a crosshair. The relative origin is the reference point for relative coordinates entered from the command line and for snap constraints. Normally the relative zero point moves automatically. For example, when constructing a sequence of lines, the relative origin always moves to the last point set. This allows the next point to be easily determined relative to the last point. Sometimes this is not desired. If you want the relative zero point to always stay at the same position until you move it manually, you can fix the position. The snap toolbar offers two tools to hold the object in place. Manual shifting of the relative zero point.
Set relative zero
CAD toolbar:
Moves the relative zero point to a new position.
Hold relative zero
CAD toolbar:
Menu:
Command:
Description:
When this switch is activated, the relative zero point is held at the current position until it is manually shifted (see above).
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