CODEWITHSUNDEEP
unity-game-engine
M. H.
M. H.

Reputation: 1

Unity Vector3.Dot wrong return value

i am coding a 2D car racing game in Unity. Right now i want to check if the car is drifting with the Vector3.Dot function but the if state always return a value unequal one so it always prints the drifttrack. This happens even if the car stands still or the car is driving ahead.

//Blickrichtung und Fahrtrichtung stimmen nicht überein
    //Driftspuren werden gezeichnet 
    if (1 != Vector3.Dot(myrigidbody2d.velocity, transform.TransformDirection(Vector3.forward)))
    { 
        Instantiate(drifttrack, tireLeft.transform.position, tireLeft.transform.rotation);
        Instantiate(drifttrack, tireRight.transform.position, tireRight.transform.rotation);
    }

Upvotes: 0

Views: 949

Answers (2)

M. H.
M. H.

Reputation: 1

Thank you all for your answers.

Unfortunately it does not work.

First I normalized the Vectors:

Vector3 velo = myrigidbody2d.velocity;
velo.Normalize();
Vector3 direc = transform.TransformDirction(Vector3.forward);
direc.Normalize();

Then I compare both and check if they are unequal:

float dot = Vector3.Dot(velo, direc);
if (!Mathf.Approximately(dot, 1f))
    {
        Instantiate(drifttrack, tireLeft.transform.position, 
        tireLeft.transform.rotation);
        Instantiate(drifttrack, tireRight.transform.position, 
        tireRight.transform.rotation);
    }

It still instantiate my drifttrack without doing anything.

Upvotes: 0

Everts
Everts

Reputation: 10701

Float are not precise, you will most likely never get 1 but something like 1.00000000001 which is not 1 for a computer.

You need to use a range or approximate:

float dot = Vector3.Dot(myrigidbody2d.velocity, transform.TransformDirection(Vector3.forward));
if(Mathf.Approximately(dot, 1f)) { }

https://docs.unity3d.com/2018.2/Documentation/ScriptReference/Mathf.Approximately.html

Upvotes: 5

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