How to stop your lines from jumping to the background grid in Rhino?

ByCADbrief Staff

Short Answer

Yes — in Rhino, the most common way to stop lines from jumping to the background grid is to turn off object snaps to the construction plane and draw with ProjectOsnap disabled. This prevents picked points from being forced onto the active CPlane. Limitation: this does not fix snaps caused by locked geometry or accidental planar constraints.

What You Need to Know Before

Warning: If Project is enabled in Osnap, Rhino can force your picked points onto the active construction plane even when the object you want is above or below it. This is a common cause of lines appearing to snap to the grid instead of true 3D geometry.

How to Stop Lines from Jumping to the Background Grid

  • Command: ProjectOsnap

  • Shortcut: None by default

  • Quick Steps:

    1. Check the Osnap panel at the bottom of the Rhino window and look for the Project toggle.
    2. If Project is on, click it to turn it off, or run ProjectOsnap and set it to Off.
    3. Start the Line command and snap again to your intended object points in a Perspective or 3D view.

Variables & Settings

  • Key Setting: Project toggle in the Osnap panel

  • Expert Setting: When Project is enabled, object snaps are projected to the current CPlane, which is useful for 2D drafting but often causes 3D lines to jump to the background grid. Turn it off for accurate 3D point picking.

Why it Fails

  • Cause 1 (Geometry): The target points are at different Z heights, but Osnap projection forces both picks onto the active construction plane.

  • Cause 2 (layers/Locks): The intended snap object may be locked or harder to select, so Rhino snaps to visible planar references instead.

  • Cause 3 (Command/Logic): You are drawing in a viewport where planar drafting aids are active, and Project overrides true 3D snap location.

Quick Fix & Best Practice

  • Quick Fix: Turn off Project in the Osnap panel, then redraw the line using object snaps in a Perspective viewport.
  • Manager’s Verdict: Leave Project off for most 3d modeling workflows. Use it only for controlled 2D drafting on a known CPlane.

FAQ

Why does Rhino snap to the grid instead of my object?
Because the Project Osnap option is likely forcing snaps onto the active CPlane.

Should I turn Grid Snap off too?
If points still jump to grid intersections, yes — disable Grid Snap as well when modeling in 3D.

Does this affect all line drawing in Rhino?
Yes, while Project is enabled, any snapped point can be projected to the CPlane during drawing commands.

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