Hit Glow Vertex Effect

using UnityEngine;
using System.Collections.Generic;

public class HitGlowEffect : MonoBehaviour {

    [SerializeField]
    MeshFilter[] _meshFilters;

    [SerializeField]
    List<HitPosition> _hitPositions = new List<HitPosition>();

    void Update() {
        if(_hitPositions.Count > 0) {
            UpdateHits();
            UpdateVertexColors();
        }
    }

    void UpdateHits() {
        for(int i = _hitPositions.Count - 1; i > -1; i--) {
            HitPosition hitPosition = _hitPositions[i];

            if(hitPosition.Time > 0)
                hitPosition.Time = Mathf.Max(hitPosition.Time - Time.deltaTime, 0);

            if(hitPosition.Time == 0)
                _hitPositions.RemoveAt(i);
            else
                _hitPositions[i] = hitPosition;
        }
    }

    void UpdateVertexColors() {
        for(int m = 0; m < _meshFilters.Length; m++) {
            MeshFilter _meshFilter = _meshFilters[m];

            Vector3[] vertices = _meshFilter.mesh.vertices;
            Color[] colors = new Color[vertices.Length];

            //_meshFilter.transform.world

            for(int i = 0; i < vertices.Length; i++) {
                Vector3 position = _meshFilter.transform.TransformPoint(vertices[i]);
                position = transform.InverseTransformPoint(position);
                colors[i] = CalculateColor(position);
            }

            _meshFilter.mesh.vertices = vertices;
            _meshFilter.mesh.colors = colors;
        }
    }

    Color CalculateColor(Vector3 position) {
        Color color = Color.clear;
        float alpha = 0;

        for(int i = 0; i < _hitPositions.Count; i++) {
            HitPosition hitPosition = _hitPositions[i];

            if(hitPosition.Distance <= 0) continue;

            float distance = (position - hitPosition.Position).sqrMagnitude;

            if(distance < hitPosition.Distance * hitPosition.Distance) {
                float finalDistance = 1 - (Mathf.Sqrt(distance) / hitPosition.Distance);

                //color += (hitPosition.Color * finalDistance * Mathf.Min(hitPosition.Time, 1));
                color = AddColors((hitPosition.Color * finalDistance * Mathf.Min(hitPosition.Time, 1)), color);
                alpha = Mathf.Max(alpha, finalDistance);
            }
        }

        color.a *= alpha;

        return color;
    }

    Color AddColors(Color colorA, Color colorB) {
        //float a = colorA.a + colorB.a * (1 - colorA.a);
        float a = colorA.a + colorB.a * (1 - colorA.a);

        if(a < 1.0e-6) return Color.clear;

        return new Color(
            (colorA.r * colorA.a + colorB.r * colorB.a * (1 - colorA.a)) / a,
            (colorA.g * colorA.a + colorB.g * colorB.a * (1 - colorA.a)) / a,
            (colorA.b * colorA.a + colorB.b * colorB.a * (1 - colorA.a)) / a,
            a
        );
    }

    Color BlendColors(Color colorA, Color colorB) {
        Color color = new Color();
        color.a = 1 - (1 - colorA.a) * (1 - colorB.a);

        if(color.a < 1.0e-6) return color;

        color.r = colorA.r * colorA.a / color.a + colorB.r * colorB.a * (1 - colorA.a) / color.a;
        color.g = colorA.r * colorA.a / color.a + colorB.g * colorB.a * (1 - colorA.a) / color.a;
        color.b = colorA.b * colorA.a / color.a + colorB.b * colorB.a * (1 - colorA.a) / color.a;

        return color;
    }

    public void AddHit(HitPosition hitPosition) {
        hitPosition.Position = transform.InverseTransformPoint(hitPosition.Position);
        _hitPositions.Add(hitPosition);
    }

    public void Reset() {
        _hitPositions.Clear();
        UpdateVertexColors();
    }

    [System.Serializable]
    public struct HitPosition {

        [SerializeField]
        Vector3 _position;

        [SerializeField]
        float _distance;

        [SerializeField, ColorUsage(true, true, 0, 10, .125f, 3)]
        Color _color;

        [SerializeField]
        float _time;

        #region Properties
        public Color Color {
            get { return _color; }
            set { _color = value; }
        }

        public float Distance {
            get { return _distance; }
            set { _distance = value; }
        }

        public Vector3 Position {
            get { return _position; }
            set { _position = value; }
        }

        public float Time {
            get { return _time; }
            set { _time = value; }
        }
        #endregion

        public HitPosition(Vector3 position, Color color, float distance, float time) {
            _position = position;
            _color = color;
            _distance = distance;
            _time = time;
        }
    }
}