Object snaps

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

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 control. 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

More than one object snap can be active at the same time. As the cursor passes 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, Tan, and Vertex 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 control

On the status bar, click Osnap.

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 check box is cleared, all previously set object snaps turn back on.

To clear check boxes

Right-click to toggle the checked/cleared state of all but the selected check box.

To clear all persistent object snaps

Right-click Disable.

Press Alt to temporarily suspend object snaps.

Note: If object snaps are disabled, press Alt to toggle them on temporarily.

One-shot object snaps

One-shot object snaps only work when Rhino is requesting a point, are turned on for one pick only, and override all persistent object snaps for that pick.

To set a one-shot object snap

Press Shift and click an object snap check box.

For example, if End, Near, and Point persistent object snaps are set in the Osnap control, 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.

Object snaps when dragging

When object snaps are on, click and hold near object snap locations to use them for the start or end locations of the drag.

To suspend object snaps for the drag, press and hold Alt.

Drag line from midpoint to circle center.

Project object snaps

The Project button on the Osnap control projects any object snap to the current construction plane. For example, in the illustration, the curve projects to the construction plane from snapped locations on an object.

See: ProjectOsnap

Simple object snaps

Simple object snaps snap to one location on an object.

Steps

Move the cursor near the target object.

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

Toolbar: Object Snap NoSnap

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

Toolbar: Object Snap Cen (Center)

Snap to the center of a circle, arc, closed polyline, centers of single surfaces with a polyline outer boundary and no holes, and annotation text bounding box.

Examples of Center object snap.

Toolbar: Object Snap End

Snap to the end of a curve, text corners, interior vertices of polylines and joined curves, the seam point on closed curves, and the "corners" of surfaces, and polysurfaces.

Examples of End object snap.

Toolbar: Object Snap Intersection (Int)

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

Examples of Intersection object snap.

Toolbar: Object Snap Knot

Snap to a knot on a curve or surface.

Examples of Knot object snap.

Toolbar: Object Snap Mid (Midpoint)

Snap to the midpoint of a curve, surface edge, or a segment of a polycurve.

Examples of Midpoint object snap.

Toolbar: Object Snap Near

Snap onto a curve or surface edge at the cursor location.

Example of the Near object snap.

Toolbar: Object Snap Perp (Perpendicular)

Snap perpendicular to a curve or surface edge.

Examples of the Perp object snap.

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

Toolbar: Object Snap Point

Snap to a point object, extrusion axis, control point, edit point, block, and text insertion points.

Also snaps to centers and corners of rectangular lights and block insertion points even if control points are not displayed.

Toolbar: Object Snap Quad (Quadrant)

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

Note

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

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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.

Toolbar: Object Snap Tan (Tangent)

Snap tangent to a curve.

Examples of Tangent object snap.

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

Vertex

Snap to a mesh vertex.

Note

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Use the CullControlPolygon to disable snapping to vertices on the back side of mesh objects.

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Mesh control points do not have to be turned on when using the Vertex snap.

Mesh vertex

The location where the edges of the mesh faces meet. The mesh vertex (plural vertices) contains x-, y-, and z-coordinates and may contain a vector normal, a color value, and texture coordinates.

Object snaps using references

Note: When picking points during these steps, use simple snaps (End, Near, Point, Midpoint, Center, Intersection, and Quadrant) for greater precision.

To access reference object snaps from the Osnap control

Press the Ctrl key and hover over the Osnap control.

The alternate reference object snaps appear.

Toolbar: Object Snap Along

Track along a line.

Along example

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

Along steps

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

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

The marker moves only along the tracking line.

Click the left mouse button to specify the location.

AlongParallel

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

AlongParallel example

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

AlongParallel steps

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

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

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

The marker moves only along the tracking line.

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

Toolbar: Object Snap Between

Snap midway between two specified locations.

Between example

Center a circle between two rectangles

Between steps

Pick the first reference point.

Pick the second reference point.

Toolbar: Object Snap From

Snap from a specified base point.

Note

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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.

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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.

From example

Center a circle four units from the endpoint of a line.

From steps

Snap the base point to the end of the line.

Type 4 and press Enter.

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

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

Toolbar: Object Snap PerpendicularFrom

Track along a line perpendicular to a curve.

PerpendicularFrom example

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

PerpendicularFrom steps

Select the curve.

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

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

The marker tracks along the perpendicular line.

Click the left mouse button to start the line.

Toolbar: Object Snap TangentFrom

Track along a line tangent to a curve.

TangentFrom example

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

TangentFrom steps

Select the circle.

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

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

The marker tracks along on the tangent line.

Click the left mouse button to start the line.

Object snaps on an object

Toolbar: Object Snap OnCurve

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

Notes

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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.

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The curve parameter displays in the status bar when moving the mouse along the curve.

OnCurve example

Select the curve to move a control point along

OnCurve steps

Select the curve.

The marker moves only along the selected curve.

Click the left mouse button to place the point.

Toolbar: Object Snap PersistentOnCurve

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

Toolbar: Object Snap OnPolysurface

Snap to and track over a polysurface for one pick.

OnPolysurface example

Place a point object on a polysurface.

OnPolysurface steps

Select the polysurface.

The marker moves only over the polysurface.

Click the left mouse button to place the points.

PersistentOnPolysurface

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

OnMesh

Snap to and track along a selected mesh object for one pick.

OnMesh steps

Select the mesh.

The marker moves only along the selected mesh.

Click the left mouse button to place the point.

PersistentOnMesh

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

Toolbar: Object Snap OnSurface

Snap to and track over a surface for one pick.

OnSurface example

Place a point object on a surface.

OnSurface steps

Select the surface.

The marker moves only over the surface.

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.

Toolbar: Object Snap PersistentOnSurface

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

Percentage

Snap to a curve a percentage from the end.

The curve is marked with temporary black points that are automatically snapped to.

If the percentage is less than 50, the curve is marked with multiple snap points. For example, when using 30, you get snap points at 30%, 60% and 90%.

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 curves 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.

Object snaps

Simple object snaps

Object snaps using references

Object snaps on an object

Isoparametric curve snapping

Related commands