Area2D, Raycast and Collision

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Nord

Hello! I've been having this issue for almost a week and am really not sure what the problem is so would love some help.

In short; I have an object that is a Node2D with a child that is an Area2D, which in turn has a Sprite and a CollisionShape2D. The Area2D node has a Collision Layer by default that I change in runtime, for when I want to break the object in question so the player can fall through.

I've also made a simple Raycast from the Camera to a random position on the screen and when it hits the above object on the default Collision Layer, it should spawn an object, which it does.

The issue; Whenever I start testing a level where I break the above object and change the Collision Layer to something the Raycast should ignore, it still hits and thus spawns a pickup in a location the player can't reach.

What I've tested so far; I've been debugging this for almost a week and the object itself does change to the correct Collision Layer (checked through print and in Remote while running the game). I changed so the Raycast can be delayed and when adding a silly amount, like 2 seconds, it can still hit an object that is broken with a different Collision Layer that it is supposed to ignore. When I fire the Raycast, it reports the wrong layer in print from the broken object it hits, even though it has changed its Collision Layer when I check. I also noticed that, if I completely remove the object in question, it still reports a hit and spawns a pickup. Not having any object present will make the Raycast not hit anything and eventually give a Stack Overflow error, so its not hitting something else than this object.

As for the setup; Area2D and its Collision Layer starts as the second option (Bit 1, value 2) and changes to the fourth option (Bit 3, value 8) when broken. Raycast is set up as space_state.intersect_ray(ray_origin, ray_end, [self], 2, false, true)

I feel like I've tried so many things to debug this and I'm not sure anymore if it's something I'm missing or a mistake I made (more likely) or just a bug.

Am using Godot 3.2.3 stable official.

Any help is greatly appreciated, thanks!

dotted

Mm. It sounds like maybe the physics engine is still retaining the object in its original collision layer state. Then you get reports because it is using 'stale' collision layers.

There might be some way to force a mask update. But I also wonder if a 'stale' representation is lingering in the physics engine.

Also check the issue tracker: https://github.com/godotengine/godot/issues/45334

It may yield clues.

Also you'd have to be using some variant of move_and_xyz you may need extra checks in order to decide to react to the collision, right?

Also what are your masks AND layers?

Nord

@dotted said: Mm. It sounds like maybe the physics engine is still retaining the object in its original collision layer state. Then you get reports because it is using 'stale' collision layers.

There might be some way to force a mask update. But I also wonder if a 'stale' representation is lingering in the physics engine.

Also check the issue tracker: https://github.com/godotengine/godot/issues/45334

It may yield clues.

Also you'd have to be using some variant of move_and_xyz you may need extra checks in order to decide to react to the collision, right?

Also what are your masks AND layers?

Thanks for your reply, I will have a look at the issue tracker when I have more time.

I'm not using any sort of move_and_xyz in my game, the object is static and the player is a RigidBody2D that I move using impulse.

The object masks the player to check for overlaps, other then that it's the layers I previously mentioned.

Is there anything I can do to solve this or do I have to wait for an update like 4.0?

I have a manual backup I can do until this works but would be nice to not have to do it.

Found that Raycast and Raycast2D have a method called force_raycast_update, too bad I use Physics2DServer :sweat_smile:

dotted

Hm. Are you changing the mask on a static body? I think static bodies are treated as just that, unchanging. So the engine assumes they are invariant after they enter the scene. I don't know if this includes removing them later during run time

Things you can try:

Use queue_free() the static element if you haven't and wait a frame or two for it to 'take'.
Make a test-destroyable version of your static but make -it- kinematic, then do as your are doing now. The difference here is both godot and the physics engines expect these types of rigid-body modes to -change-

Also impulse isn't the best way to change position except rarely. The docs mention this.

Use _integrate_forces(body_state) and do regular calculus to move things around there using forces. The call passes the body's physics state which you can fiddle with like adding forces then body. integrate_forces() or mash the body.transform. You can also get at collided objects if you turn on contact monitoring and set the max reported to something > 0

Nord

@dotted said: Hm. Are you changing the mask on a static body? I think static bodies are treated as just that, unchanging. So the engine assumes they are invariant after they enter the scene. I don't know if this includes removing them later during run time

Things you can try:

Use queue_free() the static element if you haven't and wait a frame or two for it to 'take'.

Make a test-destroyable version of your static but make -it- kinematic, then do as your are doing now. The difference here is both godot and the physics engines expect these types of rigid-body modes to -change-

Also impulse isn't the best way to change position except rarely. The docs mention this.

Use _integrate_forces(body_state) and do regular calculus to move things around there using forces. The call passes the body's physics state which you can fiddle with like adding forces then body. integrate_forces() or mash the body.transform. You can also get at collided objects if you turn on contact monitoring and set the max reported to something > 0

The object is static as in it will never move, not a static body. Will try and test a different version, even though the current one reports the correct layer.

I actually use _integrate_forces(state) to move my player and it works fine, it's because I want the player to move toward the mouse when clicked with more speed the longer you hold, be affected by drag, bounce off of walls etc.

I've just noticed something interesting when testing a bit more; I completely removed the objects from my scene and it still hits an Area2D that does not exist in the scene anymore. Afterwards, I tried re-parenting the objects to the root to check something and when I re-parented them back it showed the pivot of the old objects I've removed from my scene. Not only that but after removing some of the objects, saving the scene and playing the scene it would complain about not finding the nodes (objects) that I have removed, so what exactly is going on here?

It seems that it is, for some reason, keeping nodes that I have removed from my scene, even though they are gone when I check the list. No wonder the Raycast is hitting if it still thinks the objects are there when they aren't.

Nord

An example of what it looks like for what it shouldn't do. It should spawn on the left blue parts and not on the outer grey parts.

Nord

A small update on this issue; I've tried using CollisionShape2D and CollisionPolygon2D where I removed the collision and made new from scratch, also tried making the Area2D the root but still the same issue. It seems as soon as I add some sort of Collision to the Area2D the Raycast can detect a hit anywhere on the screen.

Nord

After testing some more; Using queue_free() does not change anything, neither does using a KinematicBody2D. I've also noticed that not all of the collision shapes cause this, only some of them.

dotted

Well you might want to file an issue with godot engine and see how the devs respond. They may very well log it as a bug or explain what your issue is. I recommend stripping the problem down a test-case project that isolates the situation without dragging in all your code (that you might not want to simply post)

Nord

I was thinking of trying to make this whole thing in 3D space instead of 2D and after playing around with a setup I can't really get it to work properly (how the level scene should be set up and how Raycast should work between 3D and 2D). I imagine having each element on top of each other in 3D space, with some distance between, and have the Camera at the very top, Raycasting down to hit any Area2D it finds. Any idea of how a setup like this would work?