Speedlines

using System.Collections.Generic;
using UnityEngine;

public class Speedlines : MonoBehaviour
{
    public Material material;

    // Start is called before the first frame update
    void Start()
    {
        camera = Camera.main;

        Vector3 topLeftCorner = camera.ViewportToWorldPoint(new Vector3(0, 1, 0));
        Vector3 bottomLeftCorner = camera.ViewportToWorldPoint(new Vector3(0, 0, 0));
        Vector3 bottomRightCorner = camera.ViewportToWorldPoint(new Vector3(1, 0, 0));

        float width = Vector3.Distance(bottomLeftCorner, bottomRightCorner);
        float height = Vector3.Distance(bottomLeftCorner, topLeftCorner);

        int horizontalCount = Mathf.RoundToInt(width * 2) * 2;
        int verticalCount = Mathf.RoundToInt(height * 2) * 2;

        for (int i = 0; horizontalCount + verticalCount > i; i++)
        {
            TrailRenderer trail = new GameObject("Trail").AddComponent<TrailRenderer>();
            trail.material = material;
            trails.Add(trail);
        }
    }

    // Update is called once per frame
    void Update()
    {
        bool run = Input.GetMouseButton(0);

        Vector3 mousePosition = Input.mousePosition;
        Vector3 worldMousePosition = camera.ScreenToWorldPoint(mousePosition);

        Vector3 newCameraPosition = camera.transform.position;

        newCameraPosition = Vector3.Lerp(worldMousePosition, newCameraPosition, Mathf.Pow(2, -10 * Time.deltaTime));

        camera.transform.position = newCameraPosition;

        Vector3 direction = Vector3.Normalize(worldMousePosition - newCameraPosition);

        Vector3 topLeftCorner = camera.ViewportToWorldPoint(new Vector3(0, 1, 0));
        Vector3 bottomLeftCorner = camera.ViewportToWorldPoint(new Vector3(0, 0, 0));
        Vector3 bottomRightCorner = camera.ViewportToWorldPoint(new Vector3(1, 0, 0));
        Vector3 center = camera.ViewportToWorldPoint(new Vector3(0.5f, 0.5f, -1));

        float width = Vector3.Distance(bottomLeftCorner, bottomRightCorner);
        float height = Vector3.Distance(bottomLeftCorner, topLeftCorner);

        int horizontalCount = Mathf.RoundToInt(width) * 2;
        int verticalCount = Mathf.RoundToInt(height) * 2;

        if (run)
        {
            HandleSpeedlines(0, horizontalCount, bottomLeftCorner, direction, center, new Vector3(1, 0, 0), 0.5f);
            HandleSpeedlines(horizontalCount, horizontalCount * 2, topLeftCorner, direction, center, new Vector3(1, 0, 0), 0.5f);
            HandleSpeedlines((horizontalCount * 2) + verticalCount, (horizontalCount * 2) + (verticalCount * 2), bottomRightCorner, direction, center, new Vector3(0, 1, 0), 0.5f);
            HandleSpeedlines(horizontalCount * 2, (horizontalCount * 2) + verticalCount, bottomLeftCorner, direction, center, new Vector3(0, 1, 0), 0.5f);
        }
    }

    private void HandleSpeedlines(int from, int to, Vector3 initialPosition, Vector3 direction, Vector3 center, Vector3 offset, float densityMultiplier)
    {
        for (int i = from; to > i; i++)
        {
            Vector3 position = initialPosition + (offset * (i - from) * densityMultiplier) + new Vector3(0, 0, 1);

            float dot = Mathf.Clamp01(Normalize(Mathf.Clamp01(Vector3.Dot(direction, Vector3.Normalize(position - center))), 0.75f, 1));
            float sin = Mathf.Sin((Mathf.Repeat(Time.time, 10) + dot) * 15);
            float cos = Mathf.Cos((Mathf.Repeat(Time.time, 10) - dot) * 15);

            trails[i].time = dot;
            trails[i].transform.position = position;
            trails[i].widthCurve = new AnimationCurve(new Keyframe(0, 0), new Keyframe(0.4f * ((sin + 1) * 0.5f), (sin + 1) * 0.5f * Random.Range(0.05f, 0.25f) * dot), new Keyframe(0.4f + (0.4f * ((cos + 1) * 0.5f)), 0));
        }
    }

    private float Normalize(float value, float min, float max) => (value - min) / (max - min);

    private new Camera camera;
    private List<TrailRenderer> trails = new List<TrailRenderer>();
}