Recycle the Road

Lesson 7 of 20 in Coddy's Unity Game: Sky Lanes course.

Seven pieces are 140 units of road. At 10 units a second it runs out in 14 seconds. Making a new piece every time one is needed, and destroying old ones, would work, but there is a cheaper way: a piece that has passed behind the runner is moved to the front and used again.

A piece is fully behind once its middle is past -chunkLength. Seven pieces in a row, so moving it forward by seven lengths puts it right after the last one:

if (chunk.position.z < -chunkLength)
{
    chunk.position += Vector3.forward * chunkLength * chunks.Count;
}

Reusing objects instead of destroying and making new ones is called pooling. Seven pieces make an endless road.

Challenge

Easy

In Road.Update, after a piece moves, move it to the front once it is fully behind, as above.

Try it yourself

using UnityEngine;

public class Runner : MonoBehaviour
{
    public float laneWidth = 2.5f;
    public float laneSpeed = 16f;
    public float jumpHeight = 1.6f;
    public float gravity = -40f;
    public float slideTime = 0.7f;

    public int lane;

    private CharacterController controller;
    private float fallSpeed;
    private float slide;

    void Start()
    {
        controller = GetComponent<CharacterController>();
    }

    void Update()
    {
        if (Input.GetKeyDown(KeyCode.A) || Input.GetKeyDown(KeyCode.LeftArrow)) lane = Mathf.Max(-1, lane - 1);
        if (Input.GetKeyDown(KeyCode.D) || Input.GetKeyDown(KeyCode.RightArrow)) lane = Mathf.Min(1, lane + 1);
        bool jump = Input.GetKeyDown(KeyCode.W) || Input.GetKeyDown(KeyCode.UpArrow) || Input.GetKeyDown(KeyCode.Space);
        if (jump && controller.isGrounded)
        {
            fallSpeed = Mathf.Sqrt(jumpHeight * -2f * gravity);
            StopSlide();
        }
        if ((Input.GetKeyDown(KeyCode.S) || Input.GetKeyDown(KeyCode.DownArrow)) && controller.isGrounded)
        {
            slide = slideTime;
            Resize(0.5f);
        }

        if (slide > 0f)
        {
            slide -= Time.deltaTime;
            if (slide <= 0f) StopSlide();
        }

        if (controller.isGrounded && fallSpeed < 0f) fallSpeed = -2f;
        fallSpeed += gravity * Time.deltaTime;

        float targetX = lane * laneWidth;
        float x = Mathf.MoveTowards(transform.position.x, targetX, laneSpeed * Time.deltaTime);
        Vector3 move = new Vector3(x - transform.position.x, fallSpeed * Time.deltaTime, 0f);
        controller.Move(move);
    }

    void StopSlide()
    {
        if (transform.localScale.y < 1f) Resize(1f);
        slide = 0f;
    }

    void Resize(float height)
    {
        controller.enabled = false;
        transform.position += Vector3.up * (height - transform.localScale.y);
        transform.localScale = new Vector3(1f, height, 1f);
        controller.enabled = true;
    }
}