Category and Mask Bits

Category and mask bits for collision filtering function similarly to Group and Mask in Defold, operating only within a single group.

While categories are limited to 64 bits, it is strongly recommended to stay within 32 bits due to potential platform differences.

Each category should be a unique power of two, ensuring clear and non-overlapping bitwise representations. For more information on bitwise operations, refer to the Defold API docs.

Example

Collision Bits:

You can use tables to define your bits.

local collision_bits = {
	PLAYER      = 1,	-- (2^0)
	ENEMY       = 2,	-- (2^1)
	GROUND      = 4,	-- (2^2)
	ITEM        = 8,	-- (2^3) 
	WALL		= 16,	-- (2^4) 
	ALL         = bit.bnot(0)  -- -1 for all results
}

Category Bit:

Each AABB can belong to a single category bit. The category bit is optional; if left blank, it will belong to ALL categories.

local group_id = daabbcc.insert_aabb(group_id, x, y, width, height, collision_bits.PLAYER)

local group_id = daabbcc.insert_gameobject(group_id, go_url, width, height, collision_bits.ENEMY)

Mask for Queries & Raycast:

You can use the bit.bor() bitwise operator to combine multiple masks in the query or raycast results. The mask bits are optional; if left blank, it will not mask.

-- Mask bits to use with queries or raycast
local mask_bits = bit.bor(collision_bits.ENEMY, collision_bits.ITEM)

local result, count =  daabbcc.query_aabb(group_id, x, y, width, height, mask_bits)
local result, count =  daabbcc.query_id_sort(group_id, aabb_id, mask_bits)
local result, count =  daabbcc.raycast_sort(group_id, start_x, start_y, end_x, end_y, mask_bits)

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