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In my project, I need to add and remove collision exceptions a numerous number of time. The goal is to let the player (RigidBody2D) walk through walls (StaticBody2D).
While the player is inside the wall, I need the collision exception. When it gets out I need to remove it.

The easiest way would be to use Player.add_collision_exception_with(Wall) at every frame in which the player is in the wall, but I am afraid it would be over-consuming in terms of CPU.

I tried to understand how the method works by looking at the source. I only have basic knowledge in C++, but what I understand is that when you call PhysicsBody2D::add_collision_exception_with(), it calls Physics2DServerSW::body_add_collision_exception(), and then Body2SW::add_exception()

When I look at the code in body2dsw.h, I can see

VSet``<``RID``>`` exceptions;
_FORCE_INLINE_ void add_exception(const RID& p_exception) { exceptions.insert(p_exception);}

Does it mean that the method Player.add_collision_exception_with(Wall) just adds Wall to a vector of RID without further heavy process ? If I add several times the same collision exception, will it test that the collision exception already exists?

Subquestion: I can't really figure out what RIDs are, could you explain it please?

in Engine by (255 points)
edited by

1 Answer

+1 vote
Best answer

When it gets out I need to remove it

You need to place an Area2D overlapping the collision shape of the StaticBody2D and connects its body_exit_shape() signal to a callback that would remove the collision exception using remove_collision_exception_with()

Also the add_collision_exception_with() should be used only one time, at the _ready() function. No need to call it on each process.

Additionally, if you need to add_collision_exception_with() on run time you could use a Area2D just before the wall is collided and using it as trigger (body_enter_shape()) add the collision exception at that moment.

Finally You can make use of the set_one_way_collision_direction() from PhysicsBody2D to allow pass walls in one direction only. See platformer demo for example of that.

Last, you can work with Layer and Collision masks.

by (659 points)
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Thank you for this precise answer (and sorry about the delay). I was working with Raycast2Ds, but I will switch to Area2Ds and dabble with collision masks and layers.
I previously tried the onewaycollision_direction, but the 90 degree tolerance was not entierly adapted to my game.

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