Need help with layers.

[scorp]

I know what bitmasks are, but due to my crappy programming skills I just don't understand how to use them.

For example, i want my shape to occupy layers 5,8 and 31.

shape->layers=(?????);
What should i type instead of "?????"?


Sorry for a stupid question, which isn't even about chipmunk.

[supertommy]

The general idea is that you want bits 5, 8 and 31 to be '1' and the rest of the bits to be '0'. I find that the following line is a nice way of accomplishing that:

Code: Select all

shape->layers = 1 << 5 | 1 << 8 | 1 << 31

Alternatively, either of the following are completely equivalent:

Code: Select all

shape->layers = 0x80000000 | 0x00000100 | 0x00000020
shape->layers = 0x80000120

(I've assumed that you meant the layer number to be zero-based, i.e.: the first layer is layer 0)

[scorp]

Big-big thx for examples!!!