# NewtonJointGetStiffness

## NewtonJointGetStiffness

dFloat NewtonJointGetStiffness(const NewtonJoint* joint)

## Usage

Get the strength coefficient bing applied to the joint reaction forces.

## Parameters

- const NewtonJoint *joint - pointer to the joint.
- dFloat stiffness - stiffness coeficient, a value between 0, and 1.0, the default value for most joint is 0.9

## Return

- stiffness coeficient.

## Remarks

- Constraint keep bodies together by calculating the exact force necessary to cancel the relative acceleration between one or more common points fixed in the two bodies. The problem is that when the bodies drift apart due to numerical integration inaccuracies, the reaction force work to pull eliminated the error but at the expense of adding extra energy to the system, does violating the rule that constraint forces must be work less. This is a inevitable situation and the only think we can do is to minimize the effect of the extra energy by dampening the force by some amount. In essence the stiffness coefficient tell Newton calculate the precise reaction force by only apply a fraction of it to the joint point. And value of 1.0 will apply the exact force, and a value of zero will apply only 10 percent.

Remark The stiffness is set to a all around value that work well for most situation, however the application can play with these parameter to make finals adjustment. A high value will make the joint stronger but more prompt to vibration of instability; a low value will make the joint more stable but weaker.