Hi,
I would like to know is there any method to solve this problem:
let say i have two objects A and B in 3D (in this case cube A and cube B )

. How can i find which face of object A are facing a face of object B?
In case my sentences are not clear, please refer to the image that i have attached. based on the image that i have attached, how can we find that the blue face of object A are facing the red face of object B?

Thank you for your help!