Curve Guide

Reference

Panel:Physics ‣ Force Fields
Type:Curve Guide

The Curve Guide is used to force particles to follow a certain path defined by a Curve Object. A typical scenario would be to move a red blood cell inside a vein, or to animate the particle flow in a motor. You can also use Curve Guide to shape certain hair strands.

Note

You can also use the Particle Edit Mode to define a path.

Since you can animate curves as a soft body or any other usual way, you may build very complex animations while keeping great control and keeping the simulation time to a minimum.

The option Curve Follow does not work for particles. Instead you have to set Angular Velocity (Particle system tab) to Spin and leave the rotation constant (i.e. do not turn on Dynamic).

Curve Guides affect all particles on the same layer, independently from their distance to the curve. If you have several guides in a layer, their fields add up to each other (the way you may have learned it in your physics course). But you can limit their influence radius by changing there Minimum Distance (see below).

Note

The Curve Guide does not affect soft bodies.

Options

../../../_images/physics_force-fields_types_curve-guide_panel.png

UI for a Curve Guide force field.

Minimum Distance
The distance from the curve, up to where the force field is effective with full strength. If you have a falloff of 0, this parameter will have no effect, because the field is effective with full strength up to Max Distance (or the infinity). Min Distance is shown with a circle at the endpoints of the curve in the 3D View.
Free
Fraction of particle life time, that is not used for the curve.
Falloff
This setting governs the strength of the guide between Min Distance and Max Distance. A falloff of 1 means a linear progression.

Path

A particle follows a Curve Guide during its lifetime, the velocity depends on its lifetime and the length of the path.

Additive
If you use Additive, the speed of the particles is also evaluated depending on the falloff.
Weights
Use Curve weights to influence the particle influence along the curve.
Maximum Distance / Use Max
The maximum influence radius. Shown by an additional circle around the curve object.

Clumping

The other settings govern the form of the force field along the curve.

Clumping Amount
The particles come together at the end of the curve (1) or they drift apart (-1).
Shape
Defines the form in which the particles come together. +0.99: the particles meet at the end of the curve. 0: linear progression along the curve. -0.99: the particles meet at the beginning of the curve.

Kink

Warning

This feature is broken in the current version, see T46776.

Changes the shape that the particles can take.

Type
Curl
The radius of the influence depends on the distance of the curve to the emitter.
Radial
A three-dimensional, standing wave.
Wave
A two-dimensional, standing wave.
Braid
Braid.
Roll
A one-dimensional, standing wave.

It is not so easy to describe the resulting shapes, so have a look at the example below.

../../../_images/physics_force-fields_types_curve-guide_kink.jpg

Kink options of a curve guide. From left to right: Radial, Wave, Braid, Roll. Animation.

Axis
Which axis to use for the offset.
Frequency
The frequency of the offset.
Amplitude
The Amplitude of the offset.
Shape
Adjust the offset to the beginning/end.

Examples

../../../_images/physics_force-fields_types_curve-guide_example.png

Curve Guide force field.