Springs

The "Edge springs" define how much the edges try to keep their original lengths. For example, by adding diagonal edges within a cube, it will become more stiff (less "jelly like"). By using edge springs, objects can keep their original shape, but still move freely with dynamics.

Springs can also be used for cloth simulation.

The Blender 2.37 Soft Body system is primarily meant to enhance animation systems (including character animation). Effects like flexible or wriggling skin are now very easy to achieve.

 

When you enable the Soft Body effect on an object, it will always be simulated forward in time (like ALT+A playback, or RightArrow key). Moving backwards in time or jumping in steps larger than 9 frames will reset the soft body back to its original position. Use the new TimeLine window playback to make tweaking Soft Body effects interactive.

 

Once you're satisfied with the simulation, you can "Bake" the simulation into a static animation system. A baked soft body plays back much more quickly, and is not dependant on simulation anymore. It is advised to bake soft bodies when rendering animations, because the simulation doesn't work correctly for Motion Blur rendering, or for rendering in small chunks via a network render system.

 

Using SoftBody for cloth simulation, especially with collision detection, is still in a testing stage. The current collision code requires improvements, which is scheduled for a later release.

 

For more precise control over cloth simulation, we will also add special edge options in a later release. Currently, all edges have an equal effect on the soft body.

Since vertices in Soft Bodies are treated as particles, the options for Force fields and Deflectors apply for them as well.

 

Please note that deflection (collisions) only work on non-deformed Meshes (not using hooks, armatures, lattices, etc). Check the Forces and Deflection notes for more information.

• Enable Soft Body
  Enables the softbody effect for the current object.
• Friction
  General "media" friction, for damping the overall motion of vertices.
• Mass
  Mass value for vertices. Larger mass slows down motion.
• Grav
  Changes the amount of gravity affecting the soft body (force in a negative Z direction)
• Speed
  You can control the internal timing of softbody with this value.
• Error Limit
  The Runge-Kutta limit; defines the step size during simulation. Small values give higher accuracy, but increase calculation time.
• Apply Deform First
  Applies the soft body after other deformations, such as those caused by Lattices or Armatures.

• Use Goal
  Use the motion from animations in the simulation (Ipo, Deform, Parents, etc). The "Goal" is the desired end-position for vertices based on this animation. How a softbody tries to achieve this goal can be defined using stiffness forces and damping.
• Goal
  The default goal weight for all vertices when no Vertex Group is assigned. If a vertex group is present and assigned, this button instead shows the name of the goal vertex group.
• G Stiff
  The spring stiffness for Goal. A low value creates very weak springs (more flexible "attatchement" to the goal), a high value creates a strong spring (a stiffer "attatchment" to the goal).
• G Damp
  The friction for Goal. Higher values dampen the effect of the goal on the soft body.
• G Min/GMax
  When you paint the values in vertex-groups (Using WeightPaint mode), you can use the GMin and Gmax to fine-tune (clamp) the weight values. The lowest vertex-weight (blue) will become GMin, the highest value (red) becomes GMax.

• Use Edges
  The edges in a Mesh Object (if there are, check Editing->Mesh Panel) can act as springs as well.
• Stiff Quads
  For quad faces, the diagonal edges are used as springs. This prevents quad faces from collapsing completely.
• E Stiff
  The spring stiffness for edges (how much the edges are stretched). A low value means very weak springs (a very elastic material), a high value is a strong spring (a stiffer material).
• E Damp
  The friction for edge springs. High values dampen the E Stiff effect.

Below is a getting started guide as well as a link to several video tutorials to get you up and running with Blender's soft bodies.

 

Tutorial Links

Tuxbot on Elysiun.com has created some great soft body video tutorials. You can find them at blendertutorials.org

This section will cover creating two of the most common types of soft bodies: "jello" objects and cloth objects. These are not in-depth tutorials (see the above links), but rather examples that should get you comftorable with Blender's soft body system.

 

"Jello" Soft Body

 

This example is relatively simple, as we won't need to worry about setting goals and creating vertex groups.

For this example, we just need a plane and an IcoSphere (2 Subdivisions). Scale the plane up a bit so its larger than the sphere. Position the IcoSphere so it's ObCenter is about 4 grid units above the plane.

Smooth out the IcoSpere by going into the Edit Buttons (F9) and activating Set Smooth and Subsurf. You can set the Subsurf level to 2 for a smoother sphere.

Now, exit edit mode and go into the Object Tab (F7). Click on the Softbody panel. Click on "Enable Soft Body." For a jello like effect, we only need to change a few settings. First, deactivate the "Use Goal" button, as we won't be needing any weighted vertices. Increase "Grav" to about 9.8 (this simulates real-life gravity). Finally, increase "E Stiff" to about 0.9. Tune "E Stiff" higher or lower to make a stiffer or more flexible jello material. (Tuning "E Stiff" to the highest level will make the sphere nearly solid).

Finally, we need to make the sphere bounce off of the plane. Select the plane and go into the Particle Interaction tab. Activate "Deflection." The default Soft Body Deflection settings are fine.

Now, press ALT-A and watch your jello bounce!

 

Cloth Soft Body

 

This example is slightly more complex than the last, but not much. Create a plane and scale it up a bit. Subdivide it twice. Go to the Edit buttons (F9) and activate Subsurf (set Subsurf level to 2 for the best results). Press "Set Smooth."

Let's add a "pin" to our cloth in one corner, so we can see the soft body effect. Create a new Vertex Group, and set "Weight" to 0. Select all vertices, and press "Assign." Now, select one corner vertex of the cloth, set "Weight" to 1.0, and press "Assign" again. This will make the vertex stay where it is during the soft body simulation.

Next, exit edit mode and go to the Softbody panel in the Object Buttons (F7). Click "Enable Soft Body." Again, increase "Grav" to 9.8. This time, leave the "Use Goal" button activated. Click the small menu button next to "Use Goal," and choose the name of the Vertex Group to use for the goal (in this case, the only choice is Group). Now, you can press ALT-A to see the cloth react to gravity. To change the elasticity of the material, tune the "E Stiff" button--smaller values will let the cloth stretch almost infinitely, while large values will cause it not to stretch at all.

 

Code by Jens Ole Wund. Integration: Ton Roosendaal. Release log and tutorial: Jason Saunders