Animate drawing LineRenderer with many position

user_13422670 0
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I have a LineRenderer with many positions and am try to animate the line from point a -> b, b ->c, etc...

First, I save all the positions of the line, then I reset the positionCount so that it is not visible at the start. But when I draw the lineRenderer in a loop, increasing positionCount over each iteration, and when drawing the next line starts, the previous line shakes a little and the width changes momentarily.

Here is code:

public float LineDrawSpeed;

void Start()
{
  lineRenderer = GetComponent<LineRenderer>();
  int lineCountInLineRenderer = lineRenderer.positionCount - 1;
  var startPositions = new Vector3[lineRenderer.positionCount];
  lineRenderer.GetPositions(startPositions);
  lineRenderer.positionCount = 1;
  StartCoroutine(LineDrawCoroutine(startPositions));
}

Here is coroutine:

IEnumerator LineDrawCoroutine(Vector3[] positions)
{
  for (int i = 0; i < positions.Length - 1; i++)
  {
    if (lineRenderer.positionCount <= i + 1)
    lineRenderer.positionCount++;

    lineRenderer.SetPosition(i, positions[i]);
    float timePass = 0f;
    while (timePass < LineDrawSpeed)
    {
      var factor = timePass / LineDrawSpeed;
      factor = Mathf.SmoothStep(0, 1, factor);

      lineRenderer.SetPosition(i + 1, Vector3.Lerp(positions[i], positions[i + 1], factor));

      timePass += Mathf.Min(Time.deltaTime, LineDrawSpeed - timePass);
      yield return null;
    }
  }
}

The mechanic works well, but something is wrong with animation.

unity3d c#
2 Answers

I found this width variation topic quite interesting. As far as I checked, there two important points to take into account.

1.- LineRenderer render billboard lines.

https://docs.huihoo.com/unity/5.3/Documentation/en/Manual/class-LineRenderer.html

Billboards are 2D elements incrusted in a 3D world, whose orientation is automatically computed so that it always faces the camera. This explains width variations along with camera movement.

2.- If the camera is not moving, take into account that: As defined in the documentation, width attribute defines: "a width value and a curve value to control the width of your trail along its length. The curve is sampled at each vertex, so its accuracy is limited by the number of vertices in your trail. The overall width of the trail is controlled by the width value."

https://docs.unity3d.com/Manual/class-LineRenderer.html

So as you are dinamically changing the vertexes of your line, the overall width of your trail might suffer changes.

So I think that your algorithim works fine, and that the width variations comes along with the line renderer component.

user_118261320

I'm pretty confident your issue lies in the fact that you are adding to the position count over and over again. Not 100% sure though.

Regardless, below is working code for how to incrementally increase the length of the line. It's just an IEnumerator, but you can just call it in StartCoroutine and it should work

This will work for a straight line, but will take some adjustments for a curved line (but I think you could make it work if you wanted to).

To explain this a bit extra, instead of incrementing and increasing the positionCount, and then adding the vector, I simply set the positionCount to the desired amount of vectors and then incrementally fill each vector in with the desired position. When setting them all right off the bat, they default to 0,0,0, so just be sure this doesn't cause any issues for you.

Below is the code I use:

//  Using IEnumerator to ensure that the line is drawn over a specific amount of time
private IEnumerator DrawLine()
{
    float renderTime = 2f;                                      // total time for full line render
    int renderSteps = 75;                                       // desired resolution of render (higher amt of steps creates smoother render)
    float timeBetweenSteps = renderTime / renderSteps;          // time between each render step

    //  Grab the LineRenderer component that is attached to the gameObject and defined in Inspector
    LineRenderer lineRenderer = yourGameObject.GetComponent<LineRenderer>();

    //  Declare the endpoint
    Vector3 endPoint = new Vector3(0, 5, 0);

    //  Take the end point and break into the amount of steps we need in order to create 
    //  fully rendered line
    //  Create an additiveVector for the forLoop that will step through the renderSteps
    //  >>  Start at zero becuase zero is the localOrigin
    Vector3 stepVector = endPoint / renderSteps;
    Vector3 additiveVector = Vector3.zero;

    //  Setting the line's position element count to the render resolution because we will
    //  have to step through 
    lineRenderer.positionCount = renderSteps;

    //  For Loop that steps through each position element in the Line
    for (int i = 0; i != lineRenderer.positionCount; i++)
    {
        lineRenderer.SetPosition(i, additiveVector);            // set the position element to the additiveVEctor
        additiveVector += stepVector;                           // add one step to the additiveVector
        yield return new WaitForSeconds(timeBetweenSteps);      // Wait the appropriate step time before repeating the loop
    }
}

Let me know if you have any questions. I hope this helps!

user_125392960
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