Making a snake-like object with a LineRenderer

Scripting
1

I’m using LineRenderers for this snake-like object (looking at it from topdown perspective), where the head of the snake is the first point of the line following its transform as it moves around, and the rest of the points are supposed to follow it on a delay. This code I have below works, but it’s not framerate independent and I just can’t figure out how to fix that – I’m already using deltaTime. At lower framerates, the points can’t keep up as well and it starts to stretch out. Any idea what’s going on here?

LineRenderer line; // The line
int lineCount = 35; // The number of points in the line
Vector2[] positions = new Vector2[35]; // An array holding the points of the line, since I can't access them directly
float speed = 300; // Speed the head of the snake is moving
float lerpSpeed = 15; // Speed the rest of the points lerp to catch up

void Update() {
        // Move snake's head and set the first line point to it
        _transform.Translate(new Vector3(speed*Time.deltaTime, 0, 0), Space.Self);
        positions[0] = _transform.position;
        line.SetPosition(0, _transform.position);
     
       // Iterate through positions and lerp each one towards the next one to follow it
       // backwards or forwards, neither way works: for (int i=positions.Length-1; i>0; i--) {
        for (int i=1; i<positions.Length; i++) {
            positions[i] = Vector2.Lerp(positions[i], positions[i-1], lerpSpeed*Time.deltaTime);
        }
     
        // Set line points
        for (int i=1; i<lineCount; i++) {
            line.SetPosition(i, new Vector3(positions[i].x, positions[i].y, 0));
        }
}
2

You can’t factor in the deltaTime to the Lerp function because it won’t work correctly. Depending on the frame rate the lerp would give you different values. Here’s a good explanation of it: Game Making Software - Construct 3

You could either fix it by writing a lerp function that works with deltaTime or just use Unity’s Unity - Scripting API: Mathf.SmoothDamp function which works properly.

If you just want a quick hack then fix your frame rate in the update function like this:

float fAccumulator = 0.0f;

void Update()
{
                // Move snake's head and set the first line point to it
                _transform.Translate(new Vector3(speed*Time.deltaTime, 0, 0), Space.Self);
                positions[0] = _transform.position;
                line.SetPosition(0, _transform.position);

                fAccumulator += Time.deltaTime;
               
                while( fAccumulator > ( 1.0f / 60.0f ) )
                {
            
                 // Iterate through positions and lerp each one towards the next one to follow it
                 // backwards or forwards, neither way works: for (int i=positions.Length-1; i>0; i--) {
                    for (int i=1; i<positions.Length; i++) {
                            positions[i] = Vector2.Lerp(positions[i], positions[i-1], 0.24f);
                    }
                   
                    fAccumulator -= ( 1.0f / 60.0f );
                }
               
                // Set line points
                for (int i=1; i<lineCount; i++) {
                        line.SetPosition(i, new Vector3(positions[i].x, positions[i].y, 0));
                }
}
3

I figured it had something to do with Lerp not playing nicely with deltaTime, but I couldn’t wrap my brain around it. Thanks a lot for the explanation and the hacky fix, which works perfectly well!