Can you explain collision binary mask for me?

[gododo]

Godot Version

4.5

Question

I found this thread and I wonder how they came up with the answer.

How can I set collision layers or masks with the bit format?

Godot Version 4.2 Question [image] I am mimicking a z axis in a top down 2d game using many collision layers. I noticed that the layers have assigned bits, but the only method to set them I could find is to manually set each one with a new line of code. Is there some way I can use the bit number instead so I can set all of them to false or true in one line?

Just set the collision_mask property to an int that packs the right binary mask

i.e. collision_mask = 233

[gertkeno]

binary masks compare each binary position of a number, 233 could be represented in binary as 0b11101001, which isn’t actually accurate for the question which uses bits 1, 8, 9, 10, and 11

collision_mask = 0b11110000001

Every 1 is essentially a true and for every 0 a false

[gododo]

collision_mask = 0b11110000001

If I understand correctly that reads the far right 1 is layer 1,(..8,9,10,11) = true ..etc. and that 0b means the rest after layer 11 are false?

Also for the layer value, I read that each layer is up by the power of 2. If I want to turn on layer 1 and 24 I’d need to add both value up as:

collision_mask = 8388609 (1+8388608) ?

[athousandships]

0b just means it is base 2, binary, the bits left to it are 0 by default

[OriginalBadBoy]

@gertkeno

Every 1 is essentially a true and for every 0 a false

More specifically you can only get to the number 233 with that combinations of 1s and 0s, thats how you know the 1s are true.

A visual / physical representation is dip switches, although obviously you can do a lot more than that in the computing version.

Binary Number System

[gododo]

by default means not reset to 0?

like if I had set layer 3 as true , then I set collision_mask = 0b01, that means 1 and 3 are true, correct?

[athousandships]

No it means all the rest are 0, if you set it to 0b01 it means you set it to 0b01 and layer 1 is set only

[gododo]

What about this question I had before.

Also for the layer value, I read that each layer is up by the power of 2. If I want to turn on layer 1 and 24 I’d need to add both value up as:

collision_mask = 8388609 (1+8388608)

Is my understanding correct? and If so, does this reset other layers to false as well?

[athousandships]

You would use | to perform bitwise operations, and it’d be best to use binary format with 0b to make it readable

[gododo]

But is my understanding correct though? I just wanna understand how it works , not necessary gonna use it.

[athousandships]

Yes it resets the other layers, it sets the mask to the value you assign, so the layers you assign are the only ones that are set