FFD Soft Bodies
 
 
 

reactor provides two different types of soft body: mesh-based soft bodies, where the underlying mesh is directly deformed, and Freeform Deformation (FFD) bodies. With an FFD body, reactor encases the original shape in a simpler FFD lattice. Then the simulation uses the lattice, rather than the object itself, as the soft body's shape. As the lattice deforms, it updates the original shape so that it, too, appears to deform.

FFD soft body deformation applied to a character’s nose

FFD bodies are less accurately modeled than mesh-based soft bodies, but also less computationally expensive to simulate. Because of this, it's generally advisable to use an FFD-based soft body when deforming a complex mesh. As a general rule of thumb, if a mesh has more than 200 triangles, it's probably a good idea to use an FFD-based soft body.

NoteWhen you view an FFD soft body in the Preview Window, you will see the FFD rather than the underlying shape. This should still give you some idea as to how the body will behave in your final animation.

Procedures

To create an FFD soft body:

  1. Create the mesh to use as the basic, non-deformed state of your soft body.
  2. Apply an FFD modifier: the FFD 2x2x2, 3x3x3, 4x4x4 or FFD(box) modifier.

    Different FFD dimensions produce different behavior. When using FFD(box), set the dimensions to a number that leaves the FFD vertices evenly distributed over the lattice. You can also use the Conform To Shape command to make the FFD lattice better represent the underlying geometry.

  3. Apply the reactor Soft Body modifier on top of the FFD modifier.
  4. in the Properties rollout of the Soft Body modifier, choose FFD-Based.

    You can now add the body to a soft body collection and simulate it as an FFD soft body.

Interface

FFD Options

FFD-based

Specifies that you want to simulate this body as an FFD soft body.

Stable Configuration

Here you can specify which configuration (position of vertices) reactor considers to be the stable (non-deformed) configuration. The FFD soft body will tend to maintain that configuration.

  • Original BoxThe stable configuration for an FFD soft body is the original, non-deformed FFD box; any animation or modification of the lattice is ignored. This is the default option.
  • FrameLets you specify the state of the FFD state at a particular keyframe as the stable configuration for the object.
Animate Transform

When on, reactor animates both the FFD lattice and the transformation of the object. In some situations, the deformation calculated by the FFD modifier is more consistent if the object transformation follows the FFD lattice.

ImportantUse this option only when the FFD encloses the entire mesh of the object, as the transformation applies to the whole mesh; that is, the whole object will be transformed.

Not animating the object transform can cause the FFD modifier to apply strange deformations.

Animating the object transform (turning on Animate Transform) fixes the problem.