Avoiding characters from standing on top of one another?

[なかの31]

So... One of the side effects of capsule colliders on characters in my game project, is that a character can stand on top of one another, which isn't actually intended.

Someone has any idea how could I prevent that from happening? Like, make the character slide off another character they're standing on top of?

[Jinx]

This tutorial shows and corrects exactly what you're asking about. Cheers! =)

https://youtu.be/SJuScDavstM?si=uXGaVc1ULLI-fvQq

[なかの31]

That's handy. I believe that if I only apply pushforce horizontally to the character might solve the issue.

Thanks :)

[なかの31]

Nope, that's not the solution to the issue I'm having.
My problem is regarding two CharacterBody3D objects.
I want to avoid one from standing on top of the other...

[Odysseus]

If you want good results you will need to compile godot from source. Luckily, the change is very small.

In physics_body_3d.cpp, there is a function (CharacterBody3D::_set_collision_direction) that looks through all the collisions and decides whether they are a floor, wall or ceiling.

This line will make sure the collider is not a CharacterBody3D:

 if (Object::cast_to<CharacterBody3D>(ObjectDB::get_instance(collision.collider_id)) == nullptr) 

You can add it just before the floor angle check to skip over CharacterBody3Ds.

Here it is in context

 ...
void CharacterBody3D::_set_collision_direction(const PhysicsServer3D::MotionResult &p_result, CollisionState &r_state, CollisionState p_apply_state) {
	r_state.state = 0;

	real_t wall_depth = -1.0;
	real_t floor_depth = -1.0;

	bool was_on_wall = collision_state.wall;
	Vector3 prev_wall_normal = wall_normal;
	int wall_collision_count = 0;
	Vector3 combined_wall_normal;
	Vector3 tmp_wall_col; // Avoid duplicate on average calculation.

	for (int i = p_result.collision_count - 1; i >= 0; i--) {
		const PhysicsServer3D::MotionCollision &collision = p_result.collisions;

		if (motion_mode == MOTION_MODE_GROUNDED) {
			// Check if any collision is floor.
		
			// CharacterBody3D is not floor 
			if (Object::cast_to<CharacterBody3D>(ObjectDB::get_instance(collision.collider_id)) == nullptr) { // <------- ADD THIS LINE
				real_t floor_angle = collision.get_angle(up_direction);
				if (floor_angle <= floor_max_angle + FLOOR_ANGLE_THRESHOLD) {
					r_state.floor = true;
					if (p_apply_state.floor && collision.depth > floor_depth) {
						collision_state.floor = true;
						floor_normal = collision.normal;
						floor_depth = collision.depth;
						_set_platform_data(collision);
					}
					continue;
				}
			} // <------- ADD THIS AS WELL

... the rest of the function can be left alone [/code]

[なかの31]

I'd prefer to use a solution that doesn't involve messing with C++ chaotic coding, even more since right now, my knowledge of C++ is about beginner level.

[なかの31]

I think I found it.
https://docs.godotengine.org/en/stable/classes/class_characterbody3d.html#class-characterbody3d-property-platform-floor-layers

But how do I use this variable? If I could remove the character collision from the platform layers, I believe might make the character not stand on top of others.

Edit: Managed to change that on the inspector, and disable for other characters. Characters still can stand on top of each other, but one character no longer moves another when moving.

[Mr. Meeseecks]

Perhaps I am not understanding the issue correctly, is your goal to have them pass-through each other, or to move the top character to "fall off" the bottom character?

If pass-through, look into setting the collision layers & masks of the characters to not interact with each other

If you want them to slide off, split your collision capsule into two stacked on top of each other (like a snowman), and set the friction of the top capsule to zero, and anything that does collide with it should slide right off.

[umop-apisdn]

Originally posted by Mr. Meeseecks:

Perhaps I am not understanding the issue correctly, is your goal to have them pass-through each other, or to move the top character to "fall off" the bottom character?

If pass-through, look into setting the collision layers & masks of the characters to not interact with each other

If you want them to slide off, split your collision capsule into two stacked on top of each other (like a snowman), and set the friction of the top capsule to zero, and anything that does collide with it should slide right off.

For more granularity, consider a cylinder with a sphere on the top and bottom.
... or depending on your collision detection needs, a vertical pair of spheres.

[なかの31]

I will try doing that later. And yep, characters colliding with each other is intended, but isn't intended to be able to stand on top of other characters.

[なかの31]

I can't change friction. There's no such setting on CollisionShape3D.