Rigidbody Add Force

Question

The docs says to use AddForce in fixed update to apply force over time. Basically what I would like is to simulate a gust of wind when the player presses the jump button. So theoretically something like

rigidbody.Addforce(transform.up*500);

Should work. Why doesn't it? my character just stands there.

Answer 1

Answer by aldonaletto · Jan 06, 2012 at 11:06 AM

When you apply a force, it causes an acceleration equal to force/mass, which increases the velocity while the force is being applied - and that's probably the problem: if you apply the force during a single physics cycle (20mS) the velocity change will be very small - even worse if you have useGravity = true.
You have two alternatives to get a more predictable result:
1- Add the velocity directly:

 rigidbody.velocity += transform.up * 10;

This is the easier alternative, since you don't have to worry about mass or gravity.

2- Use Impulse mode:

 rigidbody.Addforce(transform.up * 10, ForceMode.Impulse);

In Impulse mode, Unity applies instantly the velocity change equivalent to the force applied during 1 second. Mass and gravity will be taken into account, thus the result is a little more complicated to predict.

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Answer 2

Answer by RickLove · Jan 06, 2012 at 08:31 AM

I suspect your rigidbody is set to IsKinematic which makes it ignore forces. Try unchecking that.

Also, check out this question.

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Rigidbody Add Force

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