Blender 3D: Noob to Pro/Softbodies
A quick softbody tutorial just to demonstrate the new system. Needs some work.
The softbody system in Blender makes each edge of your object behave like a spring, and gives each vertex a weight. It is thus a very effective way to simulate physics. The easiest (and coolest :) way to explain it is to give a demonstration.
We'll make a donut shape, and then make it springy and let it drop onto a plane.
Donut shape: Ctrl-x for a new blender file if you haven't already. Be sure to delete the default cube, you won't be needing it. Goto the front view and add a circle with 8 vertices. Move the circle 5 squares to the right (holding down ctrl). Top view, press F9, and in the Mesh Tools window (in editmode) set Degr to 360, Steps to 8 and Turns to 1, make sure the 3D cursor is at the origin, and hit Spin. Select all vertices, and hit Rem Doubles. Turn on Subsurf, (which I won't bother mentioning is a modifier, found in the modifiers/shapes panel, inside the editing window) and set it to 2 iterations. We have achieved donut.
Add a plane (as a separate object) under the donut, and scale it up so that the donut has something to fall on to. It should be about 3 grid units under the donut. Press F7 and find the Particle tab, then turn on Deflection. This will make our donut bounce off the plane.
Select the donut again. Press F7 and find the Softbody tab. Hit Enable SoftBody and set Grav to 9.8 (this puts a downward force on each vertex). Turn off Use Goal (Goals are used to give each vertex a (partly) predefined position, and are too complicated for this tutorial) and turn on Stiff Quads. Hit Alt-A to animate... amazing! :)
Now some fiddling with the settings... Put E Stiff up to 0.9 to get a nice jelly effect. Alt-A again. With some objects (e.g., spheres, cylinders), if E Stiff is too low the object will collapse. This can be remedied by putting edges inside the object (i.e. through the volume) to help them keep their shape. Stiff Quads means that quads (the four-sided faces) get diagonal springs to help keep them in shape too... (insert joke about quads and working out here :).
There is huge potential in the softbody system. Try rotating the donut and the plane to get the donut to roll along the plane :) Things tend to roll better if softbody damping on the Deflection tab is turned up high.
To see a collapsing object, use a cylinder instead of a donut.
As of version 2.37a, Blender has no support for softbodies colliding into other softbodies.
Note also that the normal of the plane must be pointing towards the donut.