Object snaps

Object snaps constrain the marker to an exact location on an object such as the center of a circle or the midpoint of a line.

See Also: SmartTrack …

When Rhino asks you to choose a point, you can constrain the marker to specific parts of existing objects by turning on object snap modes. When an object snap is active, moving the cursor near a specified point on an object causes the marker to jump to that point.

Object snaps can persist from pick to pick, or can be activated for one pick only. Multiple persistent object snaps can be set in the Osnap dialog box. All object snaps behave similarly, but snap to different parts of existing geometry.

For example, the End object snap finds the endpoint of a curve. When activated, the end object snap constrains the marker to the endpoint of the curve closest the cursor.

Multiple object snaps

You can have more than one object snap active at the same time. As you pass your cursor over an object, the appropriate object snap displays.

Persistent object snaps

Use persistent objects snaps to maintain an object snap through choosing several points without having to reactivate the object snap. Only Cen, End, Int, Knot, Mid, Near, Perp, Point, Quad, and Tan object snaps can persist.

You can set the Snap radius for object snaps. This means how close you have to move the cursor to the point before the marker jumps to the point.

To display the Osnap dialog box

1. On the status bar, click Osnap.

   

2. Select or clear the desired object snap check boxes.

To turn off all persistent object snaps

• Click Disable.

• Note: Disabling the object snaps suspends their use temporarily. When the Disable checkbox is cleared, all previously set object snaps turn back on.

To clear all persistent object snaps

1. Right-click Disable.

2. Press the Alt key to temporarily suspend object snaps.

3. If object snaps are locked, press the Alt key to toggle them on temporarily.

One-shot object snaps

One-shot object snaps only work when Rhino is requesting a point and are turned on for one pick only. One-shot object snaps override all persistent object snaps for one pick. For example, if End, Near, and Point persistent object snaps are set in the Osnap dialog box, and you set the Mid object snap for one pick, End, Near, and Point will not work for that pick. After the pick, the persistent object snaps will reactivate.

Simple object snaps

Steps:

1. Move the cursor near the target object.

2. When the marker jumps to the snap location, click the left mouse button.

Center (Cen)

Snap to the center of a circle, arc, or closed polyline.

Object Snap > Center

Tools > Object Snap >Center

End

Snap to the end of a curve.

Note: The End object snap also snaps to interior vertices of polylines and joined curves, the seam point on closed curves, and the "corners" of surfaces.

Object Snap > End

Tools > Object Snap >End

Intersection (Int)

Snap to the intersections of curves, edges, and isoparametric curves on a surface.

Object Snap > Intersection

Tools > Object Snap >Intersection

Knot

Snap to a knot on a curve or surface.

Object Snap > Knot

Tools > Object Snap >Knot

MidPoint (Mid)

Snap to the midpoint of a curve

Object Snap > Midpoint

Tools > Object Snap > Midpoint

Near

Snap onto a curve at the cursor location.

Object Snap > Near

Tools > Object Snap > Near

NoSnap

If a command is active, NoSnap turns off persistent object snaps for one pick.

Object Snap > No Osnap

Tools > Object Snap > None

Perpendicular (Perp)

Snap perpendicular to a curve.

Note: The Perp object snap is not effective for the first point for a command.

Object Snap > Perpendicular To

Tools > Object Snap > Perpendicular To

Point

Snap to a point object, control point, edit point, or mesh vertex.

Object Snap > Point

Tools > Object Snap > Point

Quadrant (Quad)

Snap to the point on a curve that is at the maximum x or y point relative to the current construction plane.

Object Snap > Quadrant

Tools > Object Snap > Quadrant

Note:

• The quadrant points of circles and arcs are at the extremes in each construction plane axis direction.

• Ellipses have quadrant points at the ends of the ellipse axes if the ellipse is oblique in addition to those at the construction plane extremes.

Tangent (Tan)

Snap tangent to a curve.

Note: The Tan object snap is not effective for the first point for a command.

Object Snap > Tangent To

Tools > Object Snap > Tangent To

Complex object snaps

Notes

• These tools cannot be used in aliases.

• When picking points during these steps, use simple snaps ( End, Near, Point, Mid, Cen, Int, and Quad) for greater precision.

AlongLine

Track along a line.

Object Snap > Along Line

Tools > Object Snap > Along Line

Example:

Start a circle located on the line between the center of the circle and the end of a line.

2. Pick the start of the tracking line (the center of the circle).

3. Pick the end of the tracking line (the end of the line).

   The marker moves only along the tracking line

4. Click the left mouse button to specify the location.

AlongParallel

Track along a line parallel to a reference line between two points.

Object Snap > AlongParallel

Tools > Object Snap > Along Parallel

Example:

Start a line along a line parallel to the rectangle that passes through the circle's center.

2. Pick the start of the base line (the corner of the box).

3. Pick the end of the base line (the other corner of the box).

4. Pick the start point for parallel tracking (the center of the circle).

   The marker moves only along the tracking line.

5. Click the left mouse button to specify the location for the start of the line.

Between

Snap midway between two specified locations.

Object Snap > Between

Tools > Object Snap > Between

Example:

Center a circle between two rectangles

2. Pick the first reference point.

3. Pick the second reference point.

From

Snap from a specified base point

Object Snap > From

Tools > Object Snap > From

Notes

• The From object snap differs from the rest of the object snap because it is used to set the base point for ortho, distance constraint, angle constraint, and relative coordinate entry.

• Ortho constrains the marker to lines radiating from the last pick point. Similarly, distance constraint constrains the marker to a circle of a specified radius from the last pick point. You can set this point, without picking it, with the From object snap.

Example:

Center a circle four units from the endpoint of a line

2. Snap the base point to the end of the line.

3. Type 4 and press Enter.

   The marker is constrained to four units from the endpoint of the line.

4. Click to place the circle's center point and pick the radius.

OnCrv

Snap to and track along a selected curve for one pick.

Object Snap > On Curve

Tools > Object Snap > On Object > On Curve

Note:

• The OnCrv object snap is useful if the model is complex and Near object snap alone does not lock to the object you would like it to.

• The Near object snap can allow the point to move to a different curve.

• The OnCrv object snap lets you specify which curve.

Example:

Select the curve to move a control point along

2. Select the curve.

   The marker moves only along the selected curve.

3. Click the left mouse button to place the point.

PersistentOnCrv

Snap to and track along a selected curve until the command completes.

Object Snap > Persistent On Curve (Right click)

Tools > Object Snap > On Object > Persistent On Curve

OnSurface

Snap to and track over a surface for one pick.

Object Snap > On Surface

Tools > Object Snap > On Object > On Surface

Example:

Place a point object on a surface.

2. Select the surface.

   The marker moves only over the surface.

3. Click the left mouse button to place the point.

   Note: If you are tracking over a polysurface, the marker is restricted to the single selected face. The cursor changes shape to indicate that you cannot pick. To track over the whole polysurface, see the OnPolysrf object snap.

PersistentOnSurface

Snap to and track over a surface until the command completes.

Object Snap > Persistent On Surface (Right click)

Tools > Object Snap > On Object > Persistent On Surface

OnPolysurface

Snap to and track over a polysurface for one pick.

Object Snap > On Polysurface

Tools > Object Snap > On Object > On Polysurface

Example:

Place a point object on a polysurface.

2. Select the polysurface.

   The marker moves only over the polysurface.

3. Click the left mouse button to place the points.

PersistentOnPolySrf

Snap to and track over a polysurface until the command completes.

Object Snap > Persistent On Polysurface (Right click)

Tools > Object Snap > On Object > Persistent On Polysurface

PerpendicularFrom

Track along a line perpendicular to a curve.

Object Snap > Perpendicular From

Tools > Object Snap > Perpendicular From

Example:

Draw a line perpendicular from a line at the intersection with the circle

2. Select the curve.

   The cursor moves only along the curve. Crosshairs appear to indicate the perpendicular and tangent lines that extend from any point on the curve.

3. Pick the point on the curve to extend the perpendicular line from.

   The marker tracks along the perpendicular line.

4. Click the left mouse button to start the line.

TangentFrom

Track along a line tangent to a curve.

Object Snap > Tangent From

Tools > Object Snap > Tangent From

Example:

Draw a line tangent from the circle at the intersection with the line.

2. Select the circle.

   The marker moves only along the circle. Crosshairs indicate the perpendicular and tangent lines that extend from any point on the circle.

3. Pick the point on the circle to extend the tangent line from.

   The marker tracks along on the tangent line.

4. Click the left mouse button to start the line.

Isoparametric curve snapping

You can snap to surface isoparametric curves using the Int object snap whenever the input is constrained to a surface, for example in ExtractIsocurve, InsertKnot, OrientOnSrf, and with OnSrf, and OnPolysrf one-shot object snaps.

Isoparametric curve object snapping is "weaker" than normal object snaps. The normal object snaps are evaluated first, and only if they fail will Rhino try to snap to the isoparametric curve intersections.

Scripting one-shot object snaps

One-shot object snaps are automatically transparent. In other words, when scripting these, you do not need to use the apostrophe character to make the object snap work while a command is running.

Osnap

Sets the status of object snaps from the command line.

Steps:

• Click an option.

Notes

• This command is useful for scripting, because it can set any object snap combination from command line.

• You can temporarily suspend the effect of the object snaps with the DisableOsnap command.

DisableOsnap

Manages the state of persistent object snaps.

To temporarily turn off persistent object snaps from the dialog box

• In the Osnap dialog box, click the Disable button.

• When Object snaps are disabled, persistent object snaps are temporarily suspended.

  

To reactivate persistent object snaps from the dialog box

• In the Osnap dialog box, deactivate the Disable button.

• All persistent object snaps will be reactivated.

  

To clear all persistent object snaps from the dialog box

• In the Osnap dialog box, right-click the Disable button.

To temporarily turn off persistent object snaps from the command line

• Click an option.

Options

Enable

Disable

Toggle

ProjectOsnap

Projects object snaps from the actual snap point to the construction plane.

Steps:

• Click an option.

When Osnap projection is on, and the cursor is over an object snap point, the marker projects to the current construction plane with a white tracking line between it and the cursor.

If Planar mode is on, the ProjectOsnap command will project the object snap to the "virtual plane" that is set by the planar mode.

Options

Enable

Disable

Toggle

ShowOsnap

Turns the Osnap toolbar on, off, or toggles the current state.

Steps:

• Click an option.

Options

Show

Hide

Toggle