Calculate MaxVelocity after AddForce

Question

I am making a game in which i have a few Balls moving on their own and never stopping. Now I tried to add a Forcefield which should redirect the balls, which I did with AddForce:

ball.gameObject.GetComponent<Rigidbody2D>().AddForce(ball.transform.forward * ((ball.speed/(70f+time)) * (ball.speed/(70f+time))));

(70 and time are just numbers to regulate the strength of the push).

But that speeded up the balls which is a huge problem. Which is why I tried to clamp the velocity:

ball.gameObject.GetComponent<Rigidbody2D>().velocity = Vector3.ClampMagnitude(ball.gameObject.GetComponent<Rigidbody2D>().velocity, ball.speed/75f);

(Yes I will change the code so I dont have to get the Rigidbody 3 times.)

How would you calculate the Clamp, I have now via try and error figured out that ball.speed/75f works, but are there exact numbers? Has anyone an exact way to do it?

If you want to change direction without adding speed .. why not just change the velocity directly? — derHugo
– derHugo, Commented Jan 23 at 13:40
1. I'm not sure what you really want to do, please clarify your question. 2. Why is speeding up the ball a huge problem? 3. What is ball.speed and what is its relationship with velocity? — shingo
– shingo, Commented Jan 23 at 14:53

Pindwin · Accepted Answer · 2025-01-23 17:09:10Z

0

rigidbody.velocity is a vector - its direction defines direction of movement and its length defines speed of movement. Using these properties, you can:

Save up the velocity length (float cachedLength = rigidbody.velocity.magnitude;).
Apply the force you want to modify the direction
Change velocity length to maintain the speed: rigidbody.velocity = rigidbody.velocity.normalized * cachedLength;

This way, you accept change in direction, but not in legth of the vector.

Edit. Just noticed you are using ball.speed in your question - never used Rigidbody2D, so naming can differ, but the mathematical principle is the same.

edited Jan 23 at 17:09

answered Jan 23 at 14:36

Pindwin

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2 Comments

derHugo Jan 23 at 20:53

ball.speed has nothing to do with Rigidbody(2D)

Pindwin Jan 24 at 10:01

Sure, I don't know Rigidbody2D API, assumed just as much.

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