CODEWITHSUNDEEP
c#unity-game-engine
Mike H
Mike H

Reputation: 407

Unity 2D scripted friction equation

I am working on the friction for a square object for after it is done being pushed by the player. The block's movements are controlled purely through script using transform.Translate(velocity) each frame and only a boxcollider2D. I am speculating that because i am controlling the block's movements each frame manually is the reason i can't seem to get the boxcolliders2D's physics material 2D friction to work.

Basically, I am trying to recreate the built in physics similar to rigidbodies by using transform.translate, or use the built in physics if possible. So far, i've landed on something like this

newVelocity.x -= ( 1 / (newVelocity.x * newVelocity.x)); In an attempt to reduce the velocity.x each frame until it hits 0 and shorts out. Obviously, this falls apart when the velocity.x becomes a decimal number. I'm stumped on what i should be doing to achieve a friction similar to rigid bodies where it slows down a little at first and then much faster towards the end as it stops. Any and all help appreciated, thanks in advance!

Upvotes: 1

Views: 1485

Answers (1)

kylengelmann
kylengelmann

Reputation: 196

You could compare the signs of the velocity before and after calculating the change in velocity, and set the velocity to zero when the sign changes, like so:

newVelocity.x -= ( 1 / (newVelocity.x * newVelocity.x));
if(Mathf.Sign(previousVelocity.x) != Mathf.Sign(newVelocity.x)) {
    newVelocity.x = 0f;
}

One thing, though, is that normal friction is not calculated using the above equation, it's calculated as follows:

newVelocity.x -= frictionCoefficient*Time.fixedDeltaTime;

And with this, you wouldn't need to compare the velocity to the previous velocity as you can just say if the velocity is low, it's zero. You could still compare the previous velocity sign stuff if you wanted to though, but this is probably more efficient

if(newVelocity.x < 0.01f) {
    newVelocty.x = 0f;
}

Upvotes: 3

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