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View / Viewport title

Set CPlane

The CPlane command sets the origin and orientation of the construction plane in the active viewport.

A construction plane is like a tabletop that the cursor normally moves on. The construction plane has an origin, x and y axes, and a grid. The construction plane can be set to any orientation, and each viewport’s construction plane is independent of those in other viewports.

The construction plane represents the local coordinate system for the viewport and can be different from the world coordinate system.

Rhino’s standard viewports come with construction planes that correspond to the viewport. The default Perspective viewport, however, uses the world Top construction plane, which is the same construction plane that is used in the Top viewport.


Command-line options


The construction planes in all viewports change so their origin is at the picked location.


The Curve option sets the construction plane perpendicular to a curve.

Curve steps

  1. Select a curve to orient construction plane.
  2. Drag the construction plane's new x and y axes to a new location.


  • Use the Curve option to quickly position your construction plane at various stations along a central rail curve as preparation for doing a one rail sweep, for example. Once your construction plane is positioned, you can use drawing tools to draw a cross-section curve in the 3 D location where it needs to be. This direct drawing method can be quicker and more convenient than drawing the curve on a world plane and then trying to move and rotate it into place in 3‑D.
  • The direction of the curve affects the direction of the axes. If the construction plane does not go the direction you want, flip the direction of the curve with the Flip or Dir commands.


Type subcrv to select part of a curve as input.


The Elevation option changes the elevation (z direction) of the construction plane.

Elevation steps

  • Pick a new elevation.
    Type a distance to move the origin from its previous location.


  • Positive numbers move the construction plane up along the positive z axis.
  • Negative numbers move the construction plane down.


The Gumball option sets the construction plane to match the gumball orientation of the currently selected object.


The Object option sets the construction plane in the active viewport to an object.

Object steps

  • Select a curve, surface, or mesh face.
    The origin and tangency of the new construction plane is based on the "midpoint" of the untrimmed version of the surface.
  • In the case of a surface, the origin is placed at the midpoint of UV coordinates. The Z-axis is set to the normal direction. The X-axis is set to the U direction. The Y-axis is determined by the Right-hand rule.
  • In the case of a mesh face, the origin goes to the center of the face and the face normal determines the Z-axis. Mesh faces don't have UV directions like surfaces. So there isn't any good way of orienting the X-axis on a mesh face. The X-axis is computed from the components of the normal vector.
  • In the case of a circle or an arc, the origin will be placed at the center. The X-axis will point to the start point. The Y-axis will be 90 degrees away from the start point in the curve direction.


The Rotate option rotates the construction plane.

Rotate steps

  1. Pick the start of the rotation axis.
  2. Pick the end of the rotation axis.
  3. Type the angle to rotate the construction plane.
  4. Pick two points to specify the angle.


The Surface option sets the construction plane to match a surface. The placement is constrained so that the construction plane is tangent to the surface.

Surface steps

  1. Select a surface.
  2. Pick an origin or press Enter.
  3. Pick an x axis direction or press Enter.

Surface options


Reverses the direction.


Uses entire untrimmed underlying surface.


Moves the construction plane in the current viewport in its z direction, so its xy plane intersect the selected point.

Through steps

  • Pick a location to move the CPlane in its z direction.

Through option


Moves the construction planes in all viewports in their z directions, so their xy planes intersect the selected point.


Sets the construction plane in the active viewport parallel to the view.

View steps

  • Click View or type V.


Restores the specified default construction plane.

World steps



The 3Point option sets the construction plane in the active viewport by specifying points to establish the x, y, and z directions.

3Point steps

  1. Pick a new origin, or press Enter.
  2. Pick the x axis.
  3. Pick the y axis.

3Point options


Sets the construction plane perpendicular to the current construction plane.


Sets the construction plane z axis direction.


Restores the previously used construction plane in the current viewport.

Undo steps

  • Click Undo or type U.

Shift + Home


Restores the construction plane that was active before the Undo option was used.

Redo steps

  • Click Redo or type D.

Shift + End




Status bar


New in V8


Auto CPlane

The AutoAlignCPlane command turns Auto CPlane on/off and manages the related options.

Command-line options


Turns Auto CPlane on/off .


The alignment mode can also be set by right-clicking the Auto CPlane pane on the status bar.


Aligns the CPlane with the plane of the selected curve or surface.


Attempts to keep the X and Y axes of the CPlane aligned with the closest world axes.


Attempts to keep the CPlane Y aligned with the camera up of the view.


Changes the alignment mode through Object, World, and View.

Keyboard: Ctrl(CMD)+R


Locks the CPlane to the current position and orientation.

Keyboard: Ctrl(CMD)+1


The CPlane stays on the previously selected planar object/sub-object until another one is selected.

When the sticky mode is enabled (top), the CPlane stays on one of the planar surfaces when the cylinder or nothing is selected.

Example of using Auto CPlane

  1. Click Auto CPlane on the status bar to enable Auto Aligned CPlane.

  2. Use Sub-object selection to select a face on a polysurface by Ctrl(CMD)+Shift+Click.

  3. Draw a circle.

    The circle is co-planar with the face.

  4. Deselect the face.

  5. Select another face on the polysurface.

  6. Draw a circle.

    The second circle is co-planar with the second face.


Toolbar Menu

Not on toolbars.

Not on menus.

The CopyCPlaneToAll command changes all viewports to have the same construction planes as the specified viewport.


Toolbar Menu

Not on toolbars.

Not on menus.

The CopyCPlaneSettingsToAll command changes all viewports to have the same grid settings and snap spacing as the specified viewport.

See also


Set up a relationship between a construction plane and an object.


Manage the named construction planes list.

Use construction planes




Rhinoceros 8 © 2010-2024 Robert McNeel & Associates. 07-Jun-2024