Pipe.cs

using System.Collections;
using System.Collections.Generic;
using System.Linq;
using UnityEngine;
using UnityEngine.ProBuilder;
using UnityEngine.ProBuilder.MeshOperations;

namespace PipeDreams
{
	sealed class Pipe : MonoBehaviour
	{
		static System.Random s_Random = new System.Random();

		float m_ExtrudeSpeed = 1f;
		float m_MinExtrudeDistance = 3f;
		float m_MaxExtrudeDistance = 20f;

		ProBuilderMesh m_Mesh;
		Face[] m_ActiveFaces = new Face[1];
		List<Vector3> m_Positions;
		List<int> m_Indices = new List<int>();
		Vector3 m_ExtrudeDirection;
		float m_ExtrudeDistance;

		Face activeFace
		{
			get { return m_ActiveFaces[0]; }
			set { m_ActiveFaces[0] = value; }
		}

		public ProBuilderMesh mesh
		{
			get { return m_Mesh; }
		}

		void Awake()
		{
			m_Mesh = GetComponent<ProBuilderMesh>();
		}

		public void Begin(float extrudeSpeed, float minimumExtrudeDistance, float maximumExtrudeDistance)
		{
			m_ExtrudeSpeed = extrudeSpeed;
			m_MinExtrudeDistance = minimumExtrudeDistance;
			m_MaxExtrudeDistance = maximumExtrudeDistance;
			activeFace = m_Mesh.faces[s_Random.Next(0, m_Mesh.faceCount)];
			ChangeDirection();
		}

		void ChangeDirection()
		{
			// Extrude once to create a turn
			Face[] extrudedSides = m_Mesh.Extrude(m_ActiveFaces, ExtrudeMethod.FaceNormal, 1f);

			// Select a new active face
			activeFace = extrudedSides[s_Random.Next(0, extrudedSides.Length)];

			// Extrude again to create the extending segment
			m_Mesh.Extrude(m_ActiveFaces, ExtrudeMethod.FaceNormal, .001f);

			// Get the direction of the extruded face
			m_ExtrudeDirection = Math.Normal(m_Mesh, activeFace);

			m_Positions = m_Mesh.positions.ToList();

			// Populate the list of coincident vertex indices
			m_Mesh.GetCoincidentVertices(m_ActiveFaces, m_Indices);

			float distance = m_MinExtrudeDistance + (float) s_Random.NextDouble() * (m_MaxExtrudeDistance - m_MinExtrudeDistance);

			Ray dir =new Ray(
				m_Mesh.transform.TransformPoint(Math.Average(m_Positions, activeFace.distinctIndexes)),
				m_Mesh.transform.TransformDirection(m_ExtrudeDirection));

			if (dir.GetPoint(distance).magnitude > m_MaxExtrudeDistance * 2f)
				distance = m_MaxExtrudeDistance * 2f - dir.origin.magnitude;

			StartCoroutine(ExtrudeFace(distance));
		}

		IEnumerator ExtrudeFace(float targetDistance)
		{
			float distance = 0f;

			while (distance < targetDistance)
			{
				distance += m_ExtrudeSpeed * Time.deltaTime;

				foreach (var index in m_Indices)
					m_Positions[index] += m_ExtrudeDirection * m_ExtrudeSpeed * Time.deltaTime;

				m_Mesh.positions = m_Positions;
				m_Mesh.ToMesh();
				m_Mesh.Refresh();

				yield return null;
			}

			ChangeDirection();
		}
	}
}