Follow Path Constraint

The Follow Path constraint positions an object or bone on a Curve. The desired position can be specified in two ways:

  • Using a frame number, namely the Evaluation Time of the Curve with an optional Offset in the constraint.

  • Using a number between 0 and 1, namely the Offset Factor in the constraint.

By animating these properties, the object or bone can be made to move along the Curve. It’s also possible to make it rotate to match the Curve’s direction. Use cases include cameras on rails, vehicles on roads, boxes on conveyor belts, and so on.

To set up the constraint more quickly, select the object, add the Curve to the selection, press Ctrl-P, and click Path Constraint.

Tip

The Follow Path constraint can be combined with a tracking constraint to, for example, keep a moving camera pointed at an object.

See also

The Clamp To Constraint snaps an object or bone to a Curve based on its location.

Position Offsetting

The constraint uses its owner’s position and rotation in World Space as offsets to the position and rotation on the Curve. If Follow Curve is disabled, the offsets are added in the Curve’s Local Space. If it’s enabled, the offsets are added in the space of the current curve point, with the global Y axis corresponding to the tangent direction.

In both cases, the Curve’s scale acts as a multiplier for the position offset.

../../../_images/animation_constraints_relationship_follow-path_offset-no-constraint.png

Before adding the constraint, the cone is offset along the world Y axis.
../../../_images/animation_constraints_relationship_follow-path_offset-no-follow-curve.png

After adding the constraint, the cone is offset along the Curve’s local Y axis.
../../../_images/animation_constraints_relationship_follow-path_offset-follow-curve.png

When enabling Follow Curve, the cone is offset along the curve point’s tangent.

To have the owner perfectly positioned and aligned on the Curve, ensure its world position and rotation are both zero. This can be done by pressing Alt-G and Alt-R respectively.

Options

../../../_images/animation_constraints_relationship_follow-path_panel.png

Follow Path constraint.

Target

The Curve object to follow.

Offset Fixed Position disabled

The number of frames to subtract from the Curve’s Evaluation Time. A positive value will move the owner to an earlier point on the Curve, while a negative value will move it to a later point.

Offset Factor Fixed Position enabled

Relative position along the Curve, independent of its Evaluation Time. A value of 0 corresponds to the start of the Curve while a value of 1 corresponds to the end.

Forward Axis

The local axis of the owner that should be aligned to the Curve’s tangent direction. Requires that Follow Curve is enabled.

A negative axis will make the owner point in the opposite direction.

Up Axis

The local axis of the owner that should be aligned (as much as possible) to the global Z axis. Requires that Follow Curve is enabled.

Important

The Forward Axis and the Up Axis must be different. If they are the same, the constraint will stop working and its icon will turn red.

Fixed Position

Ignore the Curve’s Evaluation Time and position the owner using only the Offset Factor.

Despite the name of this property, the owner can still be moved over time by animating the Offset Factor.

Curve Radius

Scale the owner based on the radii of the Curve’s control points.

Follow Curve

Rotate the owner according to the Forward Axis and the Up Axis.

Animate Path

By default, the Curve’s Evaluation Time is static and the constraint owner doesn’t move. Clicking this button will animate the Evaluation Time so that it’s always equal to the current scene frame.

Of course, it’s also possible to skip this button and animate the Evaluation Time by hand.

Influence

How strongly the constraint affects the owner.

Example