Detecting collision on only one side of a rectangular physics body - Swift3

Question

I am currently working on a 2D endless runner, written in Swift3 and using Spritekit.

Short question:

Is there a way to only check for collisions on the right side of my character's rectangular physics body?

More info:

The platform on which the character runs is made of puzzle pieces and the user builds upon it as the game progresses. The character progresses left to right, in respect to the background (which goes right to left).

I want the character to automatically jump when he collides with a piece on his right side. However, any pieces that the player puts to the right of him (same Y value as the character) is of the same class as the pieces underneath him.

So the same code that checks for collision between the character and pieces to his right, and make him jump, will also make him jump as long as the game detects collision between the character and the pieces under him.

I have not been able to find another problem like mine, since usually others' characters are colliding with objects of different classes from their ground class.

Thanks!

P.S. I have tried to make my character a SKSpriteNode with two physics bodies, but I could not find any helpful documentation. If it helps any, my character also performs a looping running animation--though I can't imagine that would harm anything.

Answer 1

You could achieve that by detecting collisions with your rectangle and then deciding whether the collision was with the side of your interest or not. Here is a discussion about how to do that. Good luck!

Answer 2

Have you tried adding a non visible sub node (e.g. feetNode) to your character's sprite node and giving that sub node the physics body (class) for floor contact ?

Depending on the rest of your logic, it may allow you to use a different physics class for your character have more flexibility in collision detection.

In fact, you could probably use that approach with several sub nodes in your character's sprite node and have multiple collision behaviours for the character depending on what hits it.

Answer 3

Once you obtain the contact point of the 2 bodies that are colliding, determine which body is the one that is colliding by checking the categorymasks and then check its CGPoints x position. This x position can be compared to the other body's x position to know exactly which side it is colliding from.

if Body A's x position > Body B's x position, Body A is on the right and if not, its on the left.

As simple as that. Hope this helps!