In BGE, the user can turn off backface culling which enable the back end to not be rendered but how can you make the physics not apply to the back face too? In some engines, objects can go through planes if it’s behind the normals of the plane. I trying to figure out if theres a option to do this that I don’t know about.
Example: Like it platformers games, the player can jump underneath the platform and go through it but land on top of the platform
Nope, I don’t think you can do that unfortunately. If it is a side-scroller then you can move the object in the 3rd dimension while jumping, and moving back when it finishes it’s jump. This is unnoticeable to the player.
Unfortunately the BGE doesn’t let you do the same in 3 dimensions by using the fourth.
If you program your own physics, then it’s possible. You can choose to disregard ray checks if the player’s not going down. If you’re using Bullet, then you can make platforms non-collision enabled if you’re below them.