The Center Line Snap tool is one of several Snap Tools . This commands
becomes available whenever the
current prompt is for the selection of a 3D point.
If the center line snap command is selected then all available center lines are highlighted (colored green)
for one of them to be selected. In effect the 3D point selection is suspended while a selection of one of the
center lines is made. For the point selection to be resumed one of the center lines must be selected.
A center line is selected by moving the mouse pointer close to a highlighted center line and pressing to
select it. If none of the highlighted center lines are close to the selected point then the system issue a
Beep and center line selection continues.
The center line and point selection process can be aborted at any time using the escape key (ESC).
Once a center line is successfully selected the CAD prompt returns to the point selection. However the
movement of the cross cursor (representing the current actual 3D cursor point) is now restricted to slide
along the object center line. The cross cursor restricts itself to the nearest point on the line to the mouse
pointer position.
The Center Line Snapped Dialog
The center line snap dialog replaces the point selection dialog when the center line snap command is
selected. This dialog is designed to only allow a point along the selected center line to be selected.
Fig: Snap Center Line Dialog
These are the dialog fields of the center line snap dialog:
Object: - Combo box defining the currently selected center line. This combo box can be used to selected
or reselect the snapped center line rather than using the mouse pointer selection.
Node: - The Node combo box has a selection of all the nodes on the currently snapped center line. If the
Node combo box is used to select a node then the selected node point becomes the selected point. The
Node combo box is automatically filled when the cross cursor lands on the node during mouse cursor
movement. This simply indicates that a current mouse selection will be the node point. When the cross
cursor is pushed to an end of the line a node is always selected because a node always exist at each end.
When the cursor passes over a node somewhere along the length of the center line the 'Node' magnet
captures the cursor movement until the mouse pointer moves more than the 'Node Magnet Proximity' (in
pixels) away from the node point (note: only if the 'Node Magnets Enabled' option is checked).
End1 and End2: - define the distance of the cross cursor from each end of the center line in the 3D
environment. If a valid value is entered in either of these edit fields (i.e. greater than zero and less than
the center line length) then the point defined by the end distance is accepted as the selected point.
Point: - this edit filed holds the current 3D location of the cross cursor, but the edit field is read only and
cannot be used to specify the selected point.
Datum: - the datum field can be set to 'Absolute' or 'Relative'. This field affects the value displayed in the
Point field. It only appears when the prompt is for a second point, in which case 'Relative' means the
relative position of the current cursor point to the first selected point. If absolute is selected the displayed
point is the absolute coordinate f the cursor location (i.e. raelatve to the world origin).
Selection of the Point
The point is selected either by a mouse selection, a node selection using the node combo box, or by typing
a value into either the End1 or End2 edit box.
If the point selection is part of an object creation or object relocation process then if no node exists on the
selected object center line at the selected point, then a node is automatically created. This node is then
used to link the 'active object' (via its drag/move node) to the selected object center line node. If a node
already exists at the selected point then that node is used. The center line snap is therefore one method of
creating new node points on objects.
