How can I find out the position of a chunk from the tile coordinate?

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1

Godot Version

Godot version 4.4

Question

Hello
Chunk is 8, 8
I need: tile (-1, -1) → chunk (-1, -1) and tile (8, 8) → chunk (1, 1) etc

But this function doesn’t work well:
изображение

On video at console, I get coord chunk and coord tile:

coord chunk : (0, 0) coord tile : (-1, -1), but coord chunk : (-1, -1) coord tile : (-8, -8)

2

Oops, that was wrong.

3

Maybe:

func get_chunk(pos: Vector2) -> Vector2i:
    var tilecoord = local_to_map(pos)
    var x = int(tilecoord.x) >> 3
    var y = int(tilecoord.y) >> 3

    return Vector2i(x, y)

The right shift by three is equivalent to dividing by eight, but ought to give you correct results.

4

Thanks! It’s working

5

But, if chunk size is 16, 16?

6

Divide it by 16 then

7

My code assumes a power of two size.

1 << 1 ==  2     # b00000001 -> b00000010
1 << 2 ==  4     # b00000001 -> b00000100
1 << 3 ==  8     # b00000001 -> b00001000
1 << 4 == 16     # b00000001 -> b00010000
1 << 5 == 32     # b00000001 -> b00100000
[...]

32 >> 5 == 1     # b00100000 -> b00000001
16 >> 4 == 1     # b00010000 -> b00000001
 8 >> 3 == 1     # b00001000 -> b00000001
 4 >> 2 == 1     # b00000100 -> b00000001
 2 >> 1 == 1     # b00000010 -> b00000001

Right shift << and left shift >> shift bits in the value, which is equivalent to multiplying and dividing by powers of two, and it’s way faster than integer multiplication and division.

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