Test-Planet/Assets/Scripts/DroppingPaint.cs

using System.Collections.Generic;
using System.Linq;
using UnityEngine;
#if UNITY_EDITOR
using UnityEditor;
#endif

namespace UltraCombos
{
    [ExecuteAlways]
    public class DroppingPaint : MonoBehaviour
    {
        [SerializeField] private float size = 1;
        [SerializeField, Min(8)] private int segments = 16;
        [SerializeField] private float smooth = 3f;
        [SerializeField] private Vector2 distanceMinMax = new Vector2(1, 2);
        [SerializeField] private bool isDrop = false;
        [SerializeField] private bool isClear = false;

        private List<List<Vector2>> paints = new List<List<Vector2>>();
        private List<List<Vector2>> smoothedPaints = new List<List<Vector2>>();

        private void Update()
        {
            if (isDrop)
            {
                isDrop = false;
                Drop();
            }
            
            if (isClear)
            {
                isClear = false;
                Clear();
            }

            var t = Time.deltaTime * smooth;
            for (int i = 0; i < paints.Count; i++)
            {
                var points = paints[i];
                for (int j = 0; j < points.Count; j++)
                {
                    smoothedPaints[i][j] = Vector2.Lerp(smoothedPaints[i][j], points[j], t);
                }
            }
        }

        public void Drop()
        {
            var r = Random.Range(size * 0.1f, size * 0.2f);
            var px = Random.Range(-size * 0.4f, +size * 0.4f);
            var py = Random.Range(-size * 0.4f, +size * 0.4f);

            var angle = Mathf.PI * 2 / segments;
            var circle = Enumerable.Range(0, segments).Select(i =>
            {
                var x = px + r * Mathf.Cos(angle * i);
                var y = py + r * Mathf.Sin(angle * i);
                return new Vector2(x, y);
            }).ToList();

            var center = new Vector2(px, py);
            var minDist = size / segments * distanceMinMax.x;
            var maxDist = size / segments * distanceMinMax.y;
            
            for (int i = 0; i < paints.Count; i++)
            {
                var points = paints[i];
                var pre = points.Select(p => ApplyPaintDrop(p, center, r)).ToArray();
                var incs = pre.Select((p, k) =>
                {
                    var dist = (p - pre[(k + 1) % pre.Length]).magnitude;
                    return dist < minDist ? 0 : Mathf.CeilToInt(dist / minDist);
                }).ToArray();
                
                var newPoints = new List<Vector2>();
                for (int j = 0; j < points.Count; j++)
                {
                    var inc = incs[j];
                    if (inc == 0)
                    {
                        newPoints.Add(points[j]);
                    }
                    else
                    {
                        var p1 = points[j];
                        var p2 = points[(j + 1) % points.Count];
                        for (int k = 0; k < inc; k++)
                        {
                            var p = Vector2.Lerp(p1, p2, (float)k / inc);
                            newPoints.Add(p);
                        }
                    }
                }
                points.Clear();
                points.AddRange(newPoints);
                smoothedPaints[i].Clear();
                smoothedPaints[i].AddRange(newPoints);
                
                for (int j = 0; j < points.Count; j++)
                {
                    points[j] = ApplyPaintDrop(points[j], center, r);
                }
            }

            paints.Add(circle);
            smoothedPaints.Add(circle.Select(c => center).ToList());
        }

        public void Clear()
        {
            paints.Clear();
            smoothedPaints.Clear();
        }

        private void OnDrawGizmos()
        {
#if UNITY_EDITOR
            using var mtx = new Handles.DrawingScope(transform.localToWorldMatrix);
            Handles.DrawWireCube(Vector3.zero, Vector2.one * size);
            
            if (smoothedPaints.Count == 0)
                return;

            var dh = 1f / smoothedPaints.Count;
            var h = 0f;
            var minDist = size / segments * distanceMinMax.x;
            var maxDist = size / segments * distanceMinMax.y;
            foreach (var points in smoothedPaints)
            {
                using var col = new Handles.DrawingScope(Color.HSVToRGB(h, 0.7f, 0.8f));
                foreach (var point in points)
                {
                    Handles.DrawWireDisc(new Vector3(point.x, point.y, 0), Vector3.forward, 0.02f);
                }
                
                //Handles.DrawPolyLine(points.Select(p => new Vector3(p.x, p.y, 0)).ToArray());
                //Handles.DrawAAConvexPolygon(points.Select(p => new Vector3(p.x, p.y, 0)).ToArray());
                for (int i = 0; i < points.Count; ++i)
                {
                    var p1 = points[i];
                    var p2 = points[(i + 1) % points.Count];
                    var dist = (p1 - p2).magnitude;
                    var t = Mathf.Clamp01((dist - minDist) / (maxDist - minDist));
                    var c = Color.Lerp(Color.cyan, Color.magenta, t);
                    using var lc = new Handles.DrawingScope(c);
                    Handles.DrawLine(p1, p2);
                }
                
                h += dh;
            }
#endif
        }

        private Vector2 ApplyPaintDrop(Vector2 p, Vector2 c, float r)
        {
            var d = Vector2.Distance(p, c);
            
            if (d > r)
            {
                return c + (p - c) * Mathf.Sqrt(1 + (r * r) / (d * d));
            }

            var edge = c + (p - c) * (r / d + 0.002f);
            return ApplyPaintDrop(edge, c, r);
        }
    }
}