Unity - how to use Vector2.Reflect()

Question

I have looked everywhere including the Unity documentation but cannot seem to find any good examples of how to use Unity's Vector2.Reflect() function. I am trying to use this to control the direction of the ball (in a 2D Breakout game) when it hits a wall. It takes 2 arguments (inDirection, inNormal) but I cannot seem to figure out how to use this. Any help would be appreciated.

Unseam

Answer 1

Vector2 Reflect(Vector2 inDirection, Vector2 inNormal):

inDirection: black arrow

inNormal: red arrow

return output: green arrow

Japanese

Isn't this more of a bounce (of invisible wall defined by normal) than a reflect (around the norm vector)? A true vector reflection would be like in the image but with black arrow reversed – Holst

@Holst In the diagram, you want to reflect the vector off the blue vertical line, as if the blue line was a mirror. The diagram is correct. – Hypogastrium

@shieldgenerator7, I see there is always this perspective thought shift, when I look at the normal as the actual mirror – Holst

Answer 2

The inDirection should be the velocity of your ball and the inNormal should be the unit vector that is perpendicular to your wall.

Try putting this in your ball object:

void OnCollisionEnter(Collision collision)
{
    Vector2D inDirection = GetComponent<RigidBody2D>().velocity;
    Vector2D inNormal = collision.contacts[0].normal;
    Vector2D newVelocity = Vector2D.Reflect(inDirection, inNormal);
}

NOTE: I cannot currently test that code, so it may need tweaking in terms of the names of things.

Stupefaction

Looks like inNormal must really be a unit vector, or your result will be messed up, as Unity would apply a raw formula without normalizing it for performance. – Pylon

@Pylon That's what I was wondering too. So far my tests have shown that the ContactPoint2D.normal is always a unit vector – Hypogastrium