JoltPhysics/Jolt/Physics/Collision/ObjectLayerPairFilterMask.h

// Jolt Physics Library (https://github.com/jrouwe/JoltPhysics)
// SPDX-FileCopyrightText: 2023 Jorrit Rouwe
// SPDX-License-Identifier: MIT

#pragma once

#include <Jolt/Physics/Collision/ObjectLayer.h>

JPH_NAMESPACE_BEGIN

/// Filter class to test if two objects can collide based on their object layer. Used while finding collision pairs.
/// Uses group bits and mask bits. Two layers can collide if Object1.Group & Object2.Mask is non-zero and Object2.Group & Object1.Mask is non-zero.
/// The behavior is similar to that in e.g. Bullet.
/// This implementation works together with BroadPhaseLayerInterfaceMask and ObjectVsBroadPhaseLayerFilterMask
class ObjectLayerPairFilterMask : public ObjectLayerPairFilter
{
public:
	JPH_OVERRIDE_NEW_DELETE

	/// Number of bits for the group and mask bits
	static constexpr uint32 cNumBits = JPH_OBJECT_LAYER_BITS / 2;
	static constexpr uint32	cMask = (1 << cNumBits) - 1;

	/// Construct an ObjectLayer from a group and mask bits
	static ObjectLayer		sGetObjectLayer(uint32 inGroup, uint32 inMask = cMask)
	{
		JPH_ASSERT((inGroup & ~cMask) == 0);
		JPH_ASSERT((inMask & ~cMask) == 0);
		return ObjectLayer((inGroup & cMask) | (inMask << cNumBits));
	}

	/// Get the group bits from an ObjectLayer
	static inline uint32	sGetGroup(ObjectLayer inObjectLayer)
	{
		return uint32(inObjectLayer) & cMask;
	}

	/// Get the mask bits from an ObjectLayer
	static inline uint32	sGetMask(ObjectLayer inObjectLayer)
	{
		return uint32(inObjectLayer) >> cNumBits;
	}

	/// Returns true if two layers can collide
	virtual bool			ShouldCollide(ObjectLayer inObject1, ObjectLayer inObject2) const override
	{
		return (sGetGroup(inObject1) & sGetMask(inObject2)) != 0
			&& (sGetGroup(inObject2) & sGetMask(inObject1)) != 0;
	}
};

JPH_NAMESPACE_END