ID/Assets/Code/Lab3/Path.cs

using System;
using System.Collections.Generic;
using UnityEngine;

namespace Code.Lab3
{
    public class Path : MonoBehaviour
    {
        public List<GameObject> nodes;
        private List<PathSegment> _segments;

        private void Start()
        {
            _segments = GetSegments();
        }

        public List<PathSegment> GetSegments()
        {
            var segments = new List<PathSegment>();
            for (var i = 0; i < nodes.Count - 1; i++)
            {
                var src =  nodes[i].transform.position;
                var dst = nodes[i + 1].transform.position;
                var segment = new PathSegment(src, dst);
                segments.Add(segment);
            }
            return segments;
        }

        public float GetParam(Vector3 position, float lastParam)
        {
            PathSegment currentSegment = null;
            var tempParam = 0f;
            foreach (var ps in _segments)
            {
                tempParam += Vector3.Distance(ps.A, ps.B);
                
                if (!(lastParam <= tempParam)) continue;
                
                currentSegment = ps;
                break;
            }

            if (currentSegment == null)
                return 0;
            
            var currPos = position - currentSegment.A;
            var segmentDirection = currentSegment.B - currentSegment.A;
            segmentDirection.Normalize();
            
            var pointInSegment = Vector3.Project(currPos, segmentDirection);
            
            var param = tempParam - Vector3.Distance(currentSegment.A, currentSegment.B) + pointInSegment.magnitude;
            return param;
        }

        public Vector3 GetPosition(float param)
        {
            PathSegment currentSegment = null;
            var tempParam = 0f;

            foreach (var ps in _segments)
            {
                tempParam += Vector3.Distance(ps.A, ps.B);
                
                if (!(param <= tempParam)) continue;
                
                currentSegment = ps;
                break;
            }

            if (currentSegment == null)
                return Vector3.zero;

            var segmentDirection = currentSegment.B - currentSegment.A;
            segmentDirection.Normalize();

            var localParam = param - (tempParam - Vector3.Distance(currentSegment.A, currentSegment.B));

            var position = currentSegment.A + segmentDirection * localParam;

            return position;
        }

        private void OnDrawGizmos()
        {
            var tmp = Gizmos.color;
            Gizmos.color = Color.magenta;
            for (var i = 0; i < nodes.Count - 1; i++)
            {
                var src = nodes[i].transform.position;
                var dst = nodes[i + 1].transform.position;
                var direction = dst - src;
                Gizmos.DrawRay(src, direction);
            }
            Gizmos.color = tmp;
        }
    }
}