Tangent and Perpendicular Snapping

Related Information

Snapping

Snap Vertices

Grid Menu

Snapping - Tangent and Perpendicular

Snapping is provided for straight elements (lines, paths, and polygons) relative to curved elements. In particular this capability provides an easy way to draw a line tangent to a curve through a defined point.

There are two variations of this technique, one snaps the line to the tangent of a curve the other orients the line perpendicular to the curved element.

There are a convenient short-cut for these actions. Press and hold the key "t" ( "p" for perpendicular ) to enter the Tangent snap mode. The key is pressed in conjunction with an on-screen interactive vertex (handle) adjustment. The snap is activated if a vertex of the straight element is in motion--not when editing the curved element.

The key "n" for the mathematical term "normal" is equivalent to the "p" key. This may be easier to remember by those with a math or physics background.

These snapping actions are accessed from the Grid and Guides Menu Both of these interface elements are found near the bottom of the Grid and Guides submenu.

IMPORTANT: Vertex Snapping must be enabled for use of this tangent and Perpendicular capability. The "vt" button on the Attributes is the easiest way to turn on Vertex snapping.

These snapping actions work with normal vertex (or handle) interactive adjustments of the vertex of a straight segment of a graphic. Adjusting one end of line is a good example.

The snapping occurs relative to another graphic which must have a curved segment. To draw a line from a point tangent to a curve, first position one end of the line at the desired point, then use this snapping technique while adjusting the "other" end of the line.

The easiest way to access this snapping technique is to hold down the "t" key while adjusting one end of a line (or other straight-graphic segment). Use the "p" key for the perpendicular varient of this snapping.

This is a one-shot snapping action, slightly different than normal vertex snapping. If a solution is found the line is snapped to the exact tangent point and will remain in this orientation - you cannot "pull it away" from the snap position (as you can with normal vertex snapping). This allows one to continue to adjust the length of the precisely snapped line element after it is positioned.

The "one-shot" behavior is not limiting. To pull a line away from the snapped orientation simply lift the mouse to end the adjusting session. Lifitng the mouse will clear the tangent-snapped state. Click back down again (with the "t" key released) and normal interactinve positioning is regained.

When in "one-shot" snapped state, the length of the fixed orientation segment is still adjustable. The adjusting end will vertex snap to the exact tangent point if desired -simply position it close to the tangent point.

There are menu commands for these two snapping actions. Execute the menu command then adjust the straight-line element. The menu access provides discoverability of this capability.

This technique is not used to orient two straight graphic elements. Use Guidelines snapping found on the Grids and Guides (and the Attributes bar) to orient two lines to be parallel or perpendicular to each other. The example to the right shows how Guidelines apply to perpendicular orientations of straight elements.

The Pin and Lock properties will likely be useful after your tangent (or perpendicular) path is oriented. Pinning the angle of the line after snapping will allow further adjusting without destruction of the desired orientation.

The result when snapping a line tangent to a curved path does create an intersection, as detected with the EazyDraw Knife tool. This can be useful for construction of a smooth transition of a line to a curve.

There is another method for constructing tangents and Perpendiculars to a curve. The other method is available when the Tape Measure cursor is in use. In the Tape Measure mode, tangents are shown live when the cursor is on a curve. When the tangent indicator is showing, typing the "t" key will "drop" a tangent line on the curve. This method is useful when a tangent is needed "from" a particular point on a curve. The "p" key is used to drop a perpendicular in this mode.