koobas.hobune.stream
Is there a better method to programatically move offscreen objects?
Hey,
I'm creating a 2D vertical endless runner as my first game. I've wrote a script to place 5 wall prefabs at each side of the screen and 3 background prefabs. The camera follows the player vertically (with some dampening) and so when a prefab enters and then leaves the screen, it's moved above the highest prefab:
public class SceneBuilder : MonoBehaviour
{
public Transform lWall;
public Transform rWall;
public Transform bg;
private IList<Entry> lWalls = new List<Entry>();
private IList<Entry> rWalls = new List<Entry>();
private IList<Entry> bgs = new List<Entry>();
private float wallDistance = 3.75f;
void Awake()
{
for (int y = -2; y <= 2; y++)
{
lWalls.Add(new Entry { Prefab = (Transform)Instantiate(lWall, new Vector3(-wallDistance, y * lWall.localScale.y, 0.5f), Quaternion.identity) });
rWalls.Add(new Entry { Prefab = (Transform)Instantiate(rWall, new Vector3(wallDistance, y * rWall.localScale.y, 0.5f), Quaternion.identity) });
if (y > -2 && y < 2)
{
bgs.Add(new Entry { Prefab = (Transform)Instantiate(bg, new Vector3(0, y * bg.localScale.y, 3f), Quaternion.identity) });
}
}
}
void Update()
{
new List<IList<Entry>>() { lWalls, rWalls, bgs }.ForEach(CheckVisibility);
}
private void CheckVisibility(IList<Entry> entries)
{
foreach (var entry in entries)
{
if (!entry.BeenVisible && entry.Prefab.renderer.isVisible)
{
entry.BeenVisible = true;
}
if (!entry.WentInvisible && entry.BeenVisible && !entry.Prefab.renderer.isVisible)
{
entry.WentInvisible = true;
}
}
if (entries.Any(p => p.WentInvisible))
{
var entry = entries.Where(p => p.WentInvisible).OrderBy(p => p.Prefab.transform.position.y).First();
entry.BeenVisible = false;
entry.WentInvisible = false;
MovePrefab(entry.Prefab, entries.OrderByDescending(p => p.Prefab.transform.position.y).First().Prefab.transform.position.y);
}
}
private void MovePrefab(Transform prefab, float maxPos)
{
var height = prefab.transform.localScale.y;
if (height == 3)
{
prefab.transform.position = new Vector3(prefab.transform.position.x, maxPos + 3, prefab.transform.position.z);
}
else
{
prefab.transform.position = new Vector3(prefab.transform.position.x, maxPos + 8, prefab.transform.position.z);
}
}
private class Entry
{
public Transform Prefab { get; set; }
public bool BeenVisible { get; set; }
public bool WentInvisible { get; set; }
}
}
I want to know if there's a better way to achieve the same results that I'm not aware of. I'm experienced with C# but I'm learning Unity's API as I go so I could have missed something that would make things easier/optimal.
Rather than creating a new list in the Update function and iterating through, it'd be way more readable & efficient to place the visibility logic code in the Entry class itself.
Wouldnt have to create, reorder (twice) your list every frame
Yeah, I changed the way I implemented the code but kept that silly iteration ins$$anonymous$$d of simply calling the function directly. It's fixed now.
A couple of alternative methods to consider.
Place a trigger just offscreen. When the GameObject hits the trigger then move them. (OnTriggerEnter)
Use transform.position to figure out when an object is offscreen and move
Creating new lists every frame is going to kill you from a GC perspective. In many cases its more efficient to repopulate an existing list.
Here's an example of a script that might do the job. Use this by placing on each GameObject that is part of the background. You can set the public variables via the inspector or via code.
public float lowerLimit;
public float distanceToMoveUp;
void Update (){
if(transform.position.y < lowerLimit){
transform.position = new Vector3 (transform.position.x, transform.position.y + distanceToMoveUp, transform.position.z);
}
}
I thought of the trigger method but I'm not sure how "just offscreen" would work on different screen proportions. I guess it's a matter of trying those different aspect ratios and adjusting accordingly.
And thanks for the List tip, it was a really dumb way to make three simple function calls.
Just off screen can be a fair distance, if you need to compensate for different screen sizes
I do hope you hang around. While we have several users who are experienced Unity developers, we don't have many that are experienced with C# first.
Worth pointing out that Unity doesn't include the full C# library, there are a few random things not supported. The other key difference is that Unity developers tend to take all sorts of shortcuts and aproximations. Getting the job done fast is better then getting the job done right.
You bet I'll stick around, this is a great comunity and Unity is a lovely tool. I've implemented the trigger and the code feels smoother now. Thanks for your inputs.
