drawing line on screen

Questions & Answers
1

Hi Guys. I am working on drawing a line on touch screen. i have done perfectly but facing a problem may be not a big problem but i have no idea what to do. when i click on mouse or touch screen the line start with the position where the object is situated and draw a strait line. i don’t want the strait line to draw i want to draw a line from where i want. here is code and screen shots.
thank you.
public GameObject trailPrafab;
GameObject thisTrail;
Vector3 startPos;
Plane objPlane;

void Start()
{
    objPlane = new Plane(Camera.main.transform.forward * -1, this.transform.position);
}

// Update is called once per frame
void Update () {
    if ((Input.touchCount > 0 && Input.GetTouch(0).phase == TouchPhase.Began) || Input.GetMouseButtonDown(0)){
        thisTrail = (GameObject) Instantiate(trailPrafab, this.transform.position, Quaternion.identity);
       
        Ray mRay = Camera.main.ScreenPointToRay(Input.mousePosition);
        float rayDistance;
        if (objPlane.Raycast(mRay, out rayDistance))
            startPos = mRay.GetPoint(rayDistance);
    }
    else if(((Input.touchCount > 0 && Input.GetTouch(0).phase == TouchPhase.Moved) || Input.GetMouseButton(0)))
    {
        Ray mRay = Camera.main.ScreenPointToRay(Input.mousePosition);
        float rayDistance;
        if (objPlane.Raycast(mRay, out rayDistance))
            thisTrail.transform.position = mRay.GetPoint(rayDistance);
    }
    else if ((Input.touchCount > 0 && Input.GetTouch(0).phase == TouchPhase.Ended) || Input.GetMouseButtonUp(0))
    {
        if (Vector3.Distance(thisTrail.transform.position, startPos) < 0.1)
            Destroy(thisTrail);
    }

}

138530-ss.png

2

It looks like you’re putting the new trailPrefab in the same place as the script’s parent is positioned, right here:

thisTrail = (GameObject) Instantiate(trailPrafab, this.transform.position, Quaternion.identity);

Try changing this.transform.position to startPos instead.

3

Joshius was correct in that you need the position to be startPos HOWEVER only after startPos is calculated.

Move this line:

thisTrail = (GameObject) Instantiate(trailPrafab, startPos.position, Quaternion.identity);

under this line:

thisTrail.transform.position = mRay.GetPoint(rayDistance);