Stiffness

– How elastic that ball of personal space is.
– A high stiffness means that the vertex reacts immediately to another vertex enters their space.
– In this example I used a very simple mesh, made of only five points. I rendered the spheres around every vertex so you can appreciate better the difference between a small and a great value of Stiffness.

– First example, see how the smaller the Stiffness the more the vertexes can get close each other:

– Another example:

Blender Soft Body Self Collision Stiffness

Calculation Type

– Every vertex is surrounded with an elastic virtual sphere.
– Vertices may not penetrate the sphere of other vertices.
– Calculation Type let you adjust the size of these spheres.
– Calculation Type can be Manual, Average, Minimal, Maximal, AvMinMax
– What’s the best Calculation Type? It depends from the mesh an I’m sure a better comprehension of how Calculation Type works will help you to obtain better simulations!

– In this example I used a very simple mesh only to show how this parameter affects the radius of the spheres:

Blender Soft Body Sef Collision Mesh Sizes

– I found more useful to render videos showing the mesh winth and without the spheres instead of comparative videos, so here there are some calculations:

Manual

– When you chooose ‘Manual’ the radius of all spheres is equal to the ‘Ball Size’, in this example 0.4 BU:

Blender Soft Body Sef Collision Manual Spheres

– Here the videos, that one on the right showing the spheres:



Average

-The average length of all edges attached to the vertex is calculated and then multiplied with the Ball Size setting (0.4 BU in these examples).
– Works well with evenly distributed vertices.

– In this table the radius of each sphere when you chooose ‘Average’:

Blender Soft Body Sef Collision Average

– And these are the spheres around the vertexes:

Blender Soft Body Sef Collision Average Spheres

– Here the videos:



Minimal

– The ball size is as large as the smallest spring length of the vertex multiplied with the Ball Size (0.4 BU in these examples).


– In this table the radius of each sphere when you chooose ‘Minimal’:

Blender Soft Body Sef Collision Minimal

– And these are the spheres around the vertexes:

Blender Soft Body Sef Collision Minimal Spheres

– Here the videos:



Maximal

– In this table the radius of each sphere when you chooose ‘AvMinMax’:

Blender Soft Body Sef Collision Maximal

– And these are the spheres around the vertexes:

Blender Soft Body Sef Collision Maximal

– Here the videos:



AvMinMax

– In this table the radius of each sphere when you chooose ‘AvMinMax’:

Blender Soft Body Sef Collision AvMinMax

– And these are the spheres around the vertexes:

Blender Soft Body Sef Collision AvMinMax

– Here the videos:

Blender Soft Body Self Collision Calculation Type

Ball Size

– It is related to a spherical distance (radius) within which, if another vertex of the same mesh enters, the vertex starts to deflect in order to avoid a self-collision.
– If the Calculation Type algorythm Type is set to ‘Manual’ then the ‘Ball Size’ directly sets the ball size.
– If the Calculation Type algorythm is set to ‘Average’, Minimal’, ‘Maximal’ or ‘AvMinMax’ then ‘Ball Size’ acts as a multiplicative factor for the result of the algorythm

– In this first example I did not compare two different values as I found better to render the same scene with the spheres having the radius set in the Ball Size field (Calculation Type: Manual).
– Note how vertexes collide without touching, in this scenario 0.5 is too high:

– Another example with a smaller value, it produces a better simulation right?

– So, if we set the Ball Size to a very small value the simulation will be better? No! Not only it depends from the mesh but also too low values will let other vertices get too close and thus possibly intersect because there will not be enough time to slow them down.

– In this example I compared two values for the Ball Size parameter. A too small one (the sphere is not rendered as really too small) and a too big one, both leading to a probably unwanted result:

Blender Soft Body Self Collision Ball Size

Factor

– A force perpendicular to the edge is applied. The force scales with the projection of the relative speed on the edge ( dot product ).
– Note the force is the same if wind is blowing or if you drag the edge through the air with the same speed.
– An edge moving in its own direction feel no force.
– An edge moving perpendicular to its own direction feel maximum force.
– In between you have the forces like they are when you fly a kite.
– you can find a very good explanation here.

– Note: the soft body on the right is falling down faster and faster, the cubes seems to invert their direction but it’s only due to a stroboscopic effect ;-)

– In this second example note how the bigger the Factor values the faster the soft body begins to deform.

Blender Soft Body Aerodynamics Factor

Face

– If no vertex falls over an obstacle, the obstacle is not detected as a collider.
– In these cases face can be used for collision detection but makes solver really slow.

– As you can see, no vertex falls over the upper face of the obstacle. So the obstacle is not detected as a collider if the checkbox ‘Face’ is not enabled.

Blender Soft Body Edges Face Top View

Blender Soft Body Edges Face

Bending

– This option creates virtual connections between a vertex and the vertices connected to it’s neighbours.
– Usually related to metal flat bars. Usefult when you want to set the flexibility of an object.
– See also: Bending on Wikipedia

– In the next example you can see how Bending affects the simulation for 8 different values:

– Here you can see the mesh I used to obtain a good effect:

Blender Soft Body Edges Bending Mesh
Blender Soft Body Edges Bending