9.0

200 RIGID BODIES
DYNAMICS
DYNAMICS
RIGID BODIES 201
The sequence of events leading
to snapping: elastic deformation
(top), plastic deformation
(middle), snapping (below). A
broken spring is shaded red in
the viewport.
Once the spring has been broken, just as in real life it won’t be able to exert a force
on the attached objects any more.
For snapping to be possible, the
spring must have its plastic state
dened — that is, Below and/or
Above must be enabled on the
Plastic tab. However, you can, if
you wish, still have the spring
snap without it rst having to
undergo plastic deformation:
set the Start At parameters on
the Plastic tab and the Break tab
to the same value.
Below
Enable this option to allow the spring to break when compressed. Dene the breaking
point using the Start At parameter.
Above
Enable this option if the spring should break when stretched. Dene the breaking
point using the Start At parameter.
Start At
These two input boxes set the breaking point for the Below option (left-hand input
box) and the Above option (right-hand input box). Into the input boxes, enter the
breaking point as a percentage of the Rest Length (Elastic tab). For example, if Start
At is set to 300% and Rest Length is set to 200 m, the spring will snap once it reaches
600 meters in length.
Angular Springs
Angular springs — such as those used in old wristwatches — are springs that create
torque. Angular springs create rotational motion about the centre of mass. To dene
the spring to be angular, enable the Angular option.
Enable the Angular option to
dene the spring as angular
such as the type found in an old
wristwatch.