Unity2D C# Randomly Spawn GameObject in an Area over another GameObject

Questions & Answers
1

I’m new to Unity2D (Unity 5.0.2f1) and have been searching for a solution which I’m sure is staring me in the face!

I have a game object (essentially a road) like below (DirtTrack1):

88265-screen-shot-2017-02-17-at-35625-pm.png
88265-screen-shot-2017-02-17-at-35625-pm.png2552×716 257 KB

I have a spawner which spawns GameObjects (vehicles). I want to spawn those vehicles over this road.

I have tried the following code to do this, essentially trying to spawn the vehicle within the Y-axis area of the road by getting the bottom Y co-ordinate of the road and the top Y co-ordinate, so I get the min and max vertical positions of where I can place the vehicle:

void FixedUpdate() {

	// Repeat spawning after the period spawn
	// route has finished.
	if (!_inSpawningIteration)
		StartCoroutine (SpawnVehiclePeriodically());
}

IEnumerator SpawnVehiclePeriodically()	 
{
	// Get the max and min Y of the road
	float roadY = roadObject.transform.localPosition.y;
    float roadHalfHeight = roadObject.GetComponent<SpriteRenderer>().sprite.bounds.size.y / 2f;
	float roadMaxY = roadY + roadHalfHeight;
    float roadMinY = roadY - roadHalfHeight;

    // Pick a vehicle from the vehicle's array.
    // Then, spawn the vehicle within this Y region
    GameObject vehiclePreFab = _vehicles [random];

	// Randomize the Y position that the vehicle will enter at.
	float randomY = Random.Range (roadMinY, roadMaxY);

	// Set the position and spawn.
	Vector3 newPosition = new Vector3 (Const_RoadItemsPositionX, randomY, 0f);
	GameObject vehicle = (GameObject)GameObject.Instantiate (vehiclePreFab, newPosition, Quaternion.identity);
}

This does spawn randomly but most times it is always not within the road itself. It is either part on the road or at the outside edge of it.

I can’t figure out what I’m doing wrong here but I’m sure it is something very simple!

2

Hi, roadY is made from the roadObject.localPosition.y, but when you use Instantiate (), it expects a world position. So you have to put it back in the road object’s coordinates. Try this :

newPosition = roadObject.transform.TransformPoint (newPosition);