Dynamically update CollisionPolygon2D at runtime? [closed]

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I have a stacked area chart like the supplied image (but often slightly more complex).

Each polygon doesn't have all too many points and renders efficiently.

This chart often updates with a tween that takes ~2 seconds, changing the Polygon2Ds.

But I want to be able to highlight a specific polygon by hovering it, so I added a CollisionPolygon2D to each Polygon2D. So when updating a Polygon2D I also do:

collision.polygon = polygon.polygon

This operation works but takes several hundred milliseconds to perform so I definitely can't run it every tween loop or every frame. My best bet, I think, is to run it in the middle of the tween (since I use ease-ease). But even this lags the UI for a good half a second when the update is performed.

I think this is due to the CollisionPolygon2D needing to be rebuilt everytime a new polygon is assigned which takes a crazy long time even for simple shapes.

Any suggestions what I can do differently?

unlut · Accepted Answer · 2025-08-01 11:53:12Z

You can try these 2 options.

1- Lower resolution of your collision polygon
Instead of doing

collision.polygon = polygon.polygon

do this instead

func CalculateCollisionPolygon(points:PackedVector2Array):
    var new_points:PackedVector2Array
    const DISTANCE_THRESHOLD = 1.0
    for pt:Vector2 in points:
        var alreadyExists:bool = false
        for new_pt:Vector2 in new_points:
            if (pt.distance_to(new_pt) <= DISTANCE_THRESHOLD):
                alreadyExists = true
                break
        if (alreadyExists):
            pass
        else:
            new_points.append(pt)
    return new_points

...
...

collision.polygon = self.CalculateCollisionPolygon(polygon.polygon)

2- Use threads so UI update does not get halted.

var polygonUpdatorThread:Thread = null

...
...
#  when you want to update your polygon, instead of doing
#  collision.polygon = polygon.polygon directly, do this
polygonUpdatorThread = Thread.new()
polygonUpdatorThread.start(self.update_polygon_thread_func)

func update_polygon_thread_func():
    #  update your collision polygon points

Zoom · Accepted Answer · 2025-08-11 09:55:04Z

0

The best course of action was to skip using a CollisionPolygon2D at all and instead just check Geometry2D.is_point_in_polygon(pos, polygon.polygon) on the visual Polygon2D. Where pos is the position of the mouse.

answered Aug 11 at 9:55

Zoom

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Zain Ul Abideen Iftikhar · Accepted Answer · 2025-08-01 12:01:38Z

-2

If simplifying the polygon isn't enough, or if the polygon generation itself is a heavy operation, you can move the polygon calculation to a separate thread. This prevents the main thread (which handles UI, input, and rendering) from freezing while the calculation is in progress.

answered Aug 1 at 12:01

Zain Ul Abideen Iftikhar

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