Snapping

There are three kinds of snaps, which can be turned on and off separately: grid snaps, guide snaps, and object snaps.

 

Grid snaps

Grid Snap.tif Grid Snap: This tool, found on bottom of the screen, is a switch. When on, grid snapping is on; when off, it is off. Next to it there are two fields: one for linear distances and one for angles. All linear input that defines points in space or linear distances is affected by the linear grid snap. It applies equally to X, Y, and Z directions. A few input mechanisms define angles, such as drawing arcs or rotating objects. They are affected by the angle grid snap. For convenience, the grid snap values can be accessed directly in the text fields next to the Grid icon. To invoke the Grid Options dialog, right click over an object snap icon and choose Snap Options, or choose Snap Options from the palette menu.

 

Guide Snaps

Guides are auxiliary lines that extend infinitely long. Their purpose is to lock on to certain points along a meaningful direction. Guides are generated in one of three ways:

  1. Permanent guides are generated by the user with the Draw Guide tool ( Draw Guide.tif ), found in the Manage suite of tools. They are always drawn with black dashed lines. They can be picked, moved, rotated, and deleted. Permanent guides are located on the layer that is active when they are drawn. If that layer is turned off, the guides will also disappear. Permanent guides are saved with the project.

     

  2. Temporary guides can be generated by the user anytime object snaps are active. The cursor must snap to one of the object snaps, such as a point, interval, or segment. When this happens the user may press shift+space to create a series of guide lines through the snapped entity, according to the following rules:

     

    • When snapping to a point, guide lines are generated parallel to the X,Y, and Z directions of the current reference plane.

    • When snapping to a segment or segment interval, guide lines tangent and perpendicular to the segment at the snap point are generated, in addition to the X,Y, and Z directions, whenever they are different from the X,Y, and Z directions.

     

    At most three such sets of temporary guide lines can be active. If a fourth set is created, the oldest set is removed. Temporary guides remain associated with the object where the snap occurred. If the object is edited and changed, the temporary guides for that object are removed. Pressing shift+cmd+space (shift+ctrl+space on Windows) will delete all Temporary Guides.

     

  3. Automatic guide lines are created during dynamic input, such as when drawing, transforming, extruding, etc. Depending on the type of input, guide lines that are parallel to the X and Y directions of the reference plane, tangent, and perpendicular to a drawn segment and/or perpendicular to the reference plane are created. After the input is completed, they are automatically deleted. They only exist during the execution of the tool.

If temporary and automatic guides are drawn, they are color coded: parallel to X is red, to Y is green, and to Z is blue. Tangent, perpendicular, or other directions are magenta. Angle snaps are lilac.

 

Guide Snap Toggle.tif Guide Snap: This switch, located at the bottom of the project window, allows the user to turn guide snapping on and off. If on, and the cursor is close to a guide line, it snaps to that line. If the cursor is close to the intersection of two guide lines, it snaps to it too.

 

Guide Snap Toggle.tif Angle Snap: When on, snapable guides set at a specified angle appear to the left and right of the last point drawn. The angle is set in the field next to the Angle icon.

 

Snap to Intersection.tif Intersection Snap: When this switch is on, the cursor also snaps to the intersection of a guide with a segment. When the cursor snaps to a guide line and the shift key is held down, the snapped point remains on that guide line, no matter where the cursor is moved. In that case, the cursor point is always projected perpendicular on the guide line. When snapping to a guide, or the intersection of two guides, a solid line in the color of the type of guide (see above) is drawn from the snapped point on the guide to the guide line’s origin.

 

It is possible to delete individual lines of a snap guide. While the cursor is snapping to a guide line, hit the space bar key and that line is removed. This may be useful if too many guide lines populate the screen. For example, only the tangent direction of a snap guide may be desired. Initially the X, Y, Z, perpendicular, and tangent direction are generated as guide lines. Snapping to the X, Y, Z, and perpendicular line and hitting the space bar key removes them one at a time.

 

All temporary and automatic snap guides can be deleted by hitting the shift + space bar keys at any time.

 

Object Snaps

The Snap tool palette at the bottom of the project window contains tools that allow you to snap to parts of objects.

 

No Directional Snap.tif Object Snap: When this switch is on, snapping to parts of objects is enabled and the snap tools next to it further determine which object parts can be snapped to. They are:

Snap to Point.tif Snap to Point

 

Snap to Interval.tif Snap to Interval

 

Snap to Key Points.tif Snap to Key Points

 

Snap to Segment.tif Snap to Segment

 

Snap to Intersection.tif Snap to Intersection

 

Snap to Perpendicular.tif Snap to Perpendicular

 

Snap to Tangent.tif Snap to Tangent

 

Snap to Center.tif Snap to Center

 

All of the above are self-explanatory except the Key points, which are discussed in the next section.

 

file_menu.tiff
The Object Snap Options Dialog..

 

As with the Grid Snap Options dialog, right-click the mouse over one of the object snap icons and choose Snap Options to invoke the Object Snap Options dialog. One or more of the object snap icons can be active at the same time. The cursor will automatically snap to the object part that is closest. In addition, when the cursor is located over a segment, a preview of the possible snap choices is drawn. For example, if point, segment, and interval snaps are active and the cursor is located over a segment, small red circles are drawn for the two end points of the segment and green circles for the interval points. If the cursor is not close to any of these entities, it is snapped to the segment. If it is close to one of these points, it is snapped to it. A larger green point is drawn where the cursor is snapped to an object part. The small preview points for snap choices along a segments are color coded: segment end points are red, segment interval points are green, and intersection points of segments with other segments and guides are blue. Points tangent or perpendicular from the current point while drawing are magenta.

 

Stick To Edges When this option is enabled, the snap point will stick to the nearest snap candidate point on the edge. That is the snapping will lock onto the nearest snap point of the edge, even if the cursor is not within the pixel tolerance of the point. This is similar to how snapping working in prior versions of form•Z. This new option works with the Point, Interval, Intersection, Perpendicular or Tangent snap modes but not when Snap To Segment is enabled (as the point on the segment takes precedent).

 

file_menu.tiff
Snapping with Stick to Edges Off

 

file_menu.tiff
Snapping with Stick to Edges On

 

 

Key Points

Key points are points of an object that are critical to the shape or the controls of the shape. Examples of key points are the centers of circles and the control points of spline or nurbs objects. The key points available per type of object are listed on the right. Key points can be shown when objects are displayed in Wire Frame or Shaded Work modes and the Show Key Points option is on in the respective Options dialog.

 

Selecting the Snap To Key Point icon causes the cursor to snap to the key points of an object.

key_point_primitive.eps

a
key_point_nurbz.eps
b
Examples of key points on (a)
a partial primitive and (b) a
nurbs object.

 

Object Type

Key Points

Cube

Center of each side face

Cone

Center of bottom and apex or center of top, if the cone is truncated

Cylinder

Centers of bottom and top faces

Sphere

Center

Torus

Center. Start and end points of the torus arc, if the torus is partial

Spherical Object

Center

Composite Curve

Key points of component curves, plus corner points of any straight line segments

Spline

Control points

Arc

Start point of arc, center of arc, end point of arc

Circle

Center

Ellipse

Center

2D Enclosure

Key points of base shape

Extrusion

Key points of base shape

Convergence

Key points of base shape

3D Enclosure

Key points of base shape

Revolved Object

Key points of source object

Helix

Key points of source object

Wire Helix

Helix Key points of path object

Spiral Stair

Axis point at top and bottom of stair

Stair From Path

Key points of path object

Sweep

Key points of source and path objects

Nurbs Curve

Control points

Nurbs Object

Control points

Text

Placement point for Text At Point

The key points of different types of objects.