Blender Soft Body Physics Parameters Explained

Blender’s soft body physics engine allows creators to simulate deformable objects like jelly, rubber, cushions, and muscles. Achieving realistic movement requires a solid understanding of several key settings within the physics properties tab. This article provides a direct overview of the crucial parameters—such as Mass, Goal, Edges, and Self-Collision—that dictate how soft bodies react to gravity, forces, and collisions.

Object Mass and Friction

These fundamental settings dictate the basic physical presence of your soft body object.

• Mass: Specifies the weight of the individual vertices. Heavier vertices react more sluggishly to forces but carry more momentum, resulting in more pronounced deformation upon impact.
• Friction: Determines the resistance when the soft body slides across other collision surfaces. Higher values prevent sliding, while lower values cause the object to behave as if it is on a slippery surface.

Soft Body Goal

The Goal settings act as a magnetic force, pulling the soft body vertices toward their original, undeformed positions or animated paths. This is essential for objects that need to deform but still follow a specific motion path.

• Stiffness: Controls how tightly the vertices cling to the goal. A high stiffness value keeps the object close to its original shape, while a low value allows for significant deformation and lag behind the animation.
• Damping: Reduces the oscillation (bounce) of the vertices as they try to reach the goal. Higher damping prevents chaotic shaking and stabilizes the simulation.

Soft Body Edges (Springs)

This section treats the edges of your mesh like physical springs, controlling how the internal structure stretches and compresses when subjected to external forces.

• Pull: Defines how resistant the edges are to stretching. Lower values allow the object to stretch out easily, like chewing gum.
• Push: Determines how resistant the edges are to compressing. Lower values allow the object to squash easily, while higher values keep its structural volume intact.
• Damp (Spring Damping): Controls how quickly the spring action loses energy. High damping stops the object from bouncing endlessly after an impact, making it look more like wet clay than rubber.
• Plasticity: Controls permanent deformation. When set above zero, the object will not return to its original shape after being stretched or compressed beyond a certain threshold, simulating materials that dent or warp permanently.

Soft Body Self Collision

Without this setting enabled, a highly deformed soft body will pass through its own mesh, ruining the illusion of solidity.

• Self Collision (Toggle): Activating this forces the object to recognize its own geometry during a collision, preventing self-intersection.
• Ball Size: Specifies the calculation boundary around each vertex. Adjusting this value ensures vertices do not pass through neighboring faces without causing unrealistic jitter.