principia/lib/Box2D/Particle/b2ParticleSystem.h

/*
* Copyright (c) 2013 Google, Inc.
*
* This software is provided 'as-is', without any express or implied
* warranty.  In no event will the authors be held liable for any damages
* arising from the use of this software.
* Permission is granted to anyone to use this software for any purpose,
* including commercial applications, and to alter it and redistribute it
* freely, subject to the following restrictions:
* 1. The origin of this software must not be misrepresented; you must not
* claim that you wrote the original software. If you use this software
* in a product, an acknowledgment in the product documentation would be
* appreciated but is not required.
* 2. Altered source versions must be plainly marked as such, and must not be
* misrepresented as being the original software.
* 3. This notice may not be removed or altered from any source distribution.
*/
#ifndef B2_PARTICLb2_SYSTEM_H
#define B2_PARTICLb2_SYSTEM_H

#include <Box2D/Particle/b2Particle.h>
#include <Box2D/Dynamics/b2TimeStep.h>

/// You need not to directly access b2ParticleSystem.
/// To access particle data, use functions in b2World or b2ParticleGroup.

class b2World;
class b2Body;
class b2Shape;
class b2ParticleGroup;
class b2BlockAllocator;
class b2StackAllocator;
class b2QueryCallback;
class b2RayCastCallback;
struct b2ParticleGroupDef;
struct b2Vec2;
struct b2AABB;

struct b2ParticleContact
{
	///Indices of the respective particles making contact.
	///
	int32 indexA, indexB;
	///The logical sum of the particle behaviors that have been set.
	///
	uint32 flags;
	/// Weight of the contact. A value between 0.0f and 1.0f.
	///
	float32 weight;
	///The normalized direction from A to B.
	///
	b2Vec2 normal;
};

struct b2ParticleBodyContact
{
	/// Index of the particle making contact.
	///
	int32 index;
	/// The body making contact.
	///
	b2Body* body;
	///Weight of the contact. A value between 0.0f and 1.0f.
	///
	float32 weight;
	/// The normalized direction from the particle to the body.
	///
	b2Vec2 normal;
	/// The effective mass used in calculating force.
	///
	float32 mass;
};

class b2ParticleSystem
{

private:

	friend class b2World;
	friend class b2ParticleGroup;

	template <typename T>
	struct ParticleBuffer
	{
		ParticleBuffer()
		{
			data = NULL;
			userSuppliedCapacity = 0;
		}
		T* data;
		int32 userSuppliedCapacity;
	};

	/// Used for detecting particle contacts
	struct Proxy
	{
		int32 index;
		uint32 tag;
		friend inline bool operator<(const Proxy &a, const Proxy &b)
		{
			return a.tag < b.tag;
		}
		friend inline bool operator<(uint32 a, const Proxy &b)
		{
			return a < b.tag;
		}
		friend inline bool operator<(const Proxy &a, uint32 b)
		{
			return a.tag < b;
		}
	};

	/// Connection between two particles
	struct Pair
	{
		int32 indexA, indexB;
		uint32 flags;
		float32 strength;
		float32 distance;
	};

	/// Connection between three particles
	struct Triad
	{
		int32 indexA, indexB, indexC;
		uint32 flags;
		float32 strength;
		b2Vec2 pa, pb, pc;
		float32 ka, kb, kc, s;
	};

	// Callback used with b2VoronoiDiagram.
	class CreateParticleGroupCallback
	{
	public:
		void operator()(int32 a, int32 b, int32 c) const;
		b2ParticleSystem* system;
		const b2ParticleGroupDef* def;
		int32 firstIndex;
	};

	// Callback used with b2VoronoiDiagram.
	class JoinParticleGroupsCallback
	{
	public:
		void operator()(int32 a, int32 b, int32 c) const;
		b2ParticleSystem* system;
		b2ParticleGroup* groupA;
		b2ParticleGroup* groupB;
	};

	/// All particle types that require creating pairs
	static const int32 k_pairFlags =
		b2_springParticle;
	/// All particle types that require creating triads
	static const int32 k_triadFlags =
		b2_elasticParticle;
	/// All particle types that require computing depth
	static const int32 k_noPressureFlags =
		b2_powderParticle;

	b2ParticleSystem();
	~b2ParticleSystem();

	template <typename T> T* ReallocateBuffer(T* buffer, int32 oldCapacity, int32 newCapacity);
	template <typename T> T* ReallocateBuffer(T* buffer, int32 userSuppliedCapacity, int32 oldCapacity, int32 newCapacity, bool deferred);
	template <typename T> T* ReallocateBuffer(ParticleBuffer<T>* buffer, int32 oldCapacity, int32 newCapacity, bool deferred);
	template <typename T> T* RequestParticleBuffer(T* buffer);

	int32 CreateParticle(const b2ParticleDef& def);
	void DestroyParticle(int32 index, bool callDestructionListener);
	// Destroy particles in the specified shape with the transform xf applied
	// optionally calling the destruction listener for particles that are
	// destroyed.
	int32 DestroyParticlesInShape(const b2Shape& shape, const b2Transform& xf,
	                              bool callDestructionListener);
	void DestroyParticlesInGroup(b2ParticleGroup* group,
	                             bool callDestructionListener);
	b2ParticleGroup* CreateParticleGroup(const b2ParticleGroupDef& def);
	void JoinParticleGroups(b2ParticleGroup* groupA, b2ParticleGroup* groupB);
	void DestroyParticleGroup(b2ParticleGroup* group);
	void ComputeDepthForGroup(b2ParticleGroup* group);

	void AddContact(int32 a, int32 b);
	void UpdateContacts(bool exceptZombie);
	void UpdateBodyContacts();

	void Solve(const b2TimeStep& step);
	void SolveCollision(const b2TimeStep& step);
	void SolvePressure(const b2TimeStep& step);
	void SolveDamping(const b2TimeStep& step);
	void SolveWall(const b2TimeStep& step);
	void SolveRigid(const b2TimeStep& step);
	void SolveElastic(const b2TimeStep& step);
	void SolveSpring(const b2TimeStep& step);
	void SolveTensile(const b2TimeStep& step);
	void SolveViscous(const b2TimeStep& step);
	void SolvePowder(const b2TimeStep& step);
	void SolveSolid(const b2TimeStep& step);
	void SolveColorMixing(const b2TimeStep& step);
	void SolveZombie();
	void RotateBuffer(int32 start, int32 mid, int32 end);

	void SetParticleRadius(float32 radius);
	float32 GetParticleRadius() const;
	void SetParticleDensity(float32 density);
	float32 GetParticleDensity() const;
	void SetParticleGravityScale(float32 gravityScale);
	float32 GetParticleGravityScale() const;
	void SetParticleDamping(float32 damping);
	float32 GetParticleDamping() const;
	float32 GetCriticalVelocity(const b2TimeStep& step) const;
	float32 GetCriticalVelocitySquared(const b2TimeStep& step) const;
	float32 GetCriticalPressure(const b2TimeStep& step) const;
	float32 GetParticleStride() const;
	float32 GetParticleMass() const;
	float32 GetParticleInvMass() const;

	b2ParticleGroup* GetParticleGroupList();
	const b2ParticleGroup* GetParticleGroupList() const;
	int32 GetParticleGroupCount() const;
	int32 GetParticleCount() const;
	int32 GetParticleMaxCount() const;
	void SetParticleMaxCount(int32 count);
	uint32* GetParticleFlagsBuffer();
    float32* GetParticleAccumulationBuffer();
	b2Vec2* GetParticlePositionBuffer();
	b2Vec2* GetParticleVelocityBuffer();
	b2ParticleColor* GetParticleColorBuffer();
	void** GetParticleUserDataBuffer();
	const uint32* GetParticleFlagsBuffer() const;
	const b2Vec2* GetParticlePositionBuffer() const;
	const b2Vec2* GetParticleVelocityBuffer() const;
	const b2ParticleColor* GetParticleColorBuffer() const;
	const b2ParticleGroup* const* GetParticleGroupBuffer() const;
	void* const* GetParticleUserDataBuffer() const;
	template <typename T> void SetParticleBuffer(ParticleBuffer<T>* buffer, T* newBufferData, int32 newCapacity);
	void SetParticleFlagsBuffer(uint32* buffer, int32 capacity);
	void SetParticlePositionBuffer(b2Vec2* buffer, int32 capacity);
	void SetParticleVelocityBuffer(b2Vec2* buffer, int32 capacity);
	void SetParticleColorBuffer(b2ParticleColor* buffer, int32 capacity);
	b2ParticleGroup* const* GetParticleGroupBuffer();
	void SetParticleUserDataBuffer(void** buffer, int32 capacity);

	void QueryAABB(b2QueryCallback* callback, const b2AABB& aabb) const;
	void RayCast(b2RayCastCallback* callback, const b2Vec2& point1, const b2Vec2& point2) const;
	float32 ComputeParticleCollisionEnergy() const;

	int32 m_timestamp;
	int32 m_allParticleFlags;
	int32 m_allGroupFlags;
	float32 m_density;
	float32 m_inverseDensity;
	float32 m_gravityScale;
	float32 m_particleDiameter;
	float32 m_inverseDiameter;
	float32 m_squaredDiameter;

	int32 m_count;
	int32 m_internalAllocatedCapacity;
	int32 m_maxCount;
	ParticleBuffer<uint32> m_flagsBuffer;
	ParticleBuffer<b2Vec2> m_positionBuffer;
	ParticleBuffer<b2Vec2> m_velocityBuffer;
	float32* m_dataBuffer;
	float32* m_accumulationBuffer; // temporary values
	b2Vec2* m_accumulation2Buffer; // temporary vector values
	float32* m_depthBuffer; // distance from the surface
	ParticleBuffer<b2ParticleColor> m_colorBuffer;
	b2ParticleGroup** m_groupBuffer;
	ParticleBuffer<void*> m_userDataBuffer;

	int32 m_proxyCount;
	int32 m_proxyCapacity;
	Proxy* m_proxyBuffer;

  public:
	int32 m_contactCount;
	int32 m_contactCapacity;
	b2ParticleContact* m_contactBuffer;
  private:

	int32 m_bodyContactCount;
	int32 m_bodyContactCapacity;
	b2ParticleBodyContact* m_bodyContactBuffer;

	int32 m_pairCount;
	int32 m_pairCapacity;
	Pair* m_pairBuffer;

	int32 m_triadCount;
	int32 m_triadCapacity;
	Triad* m_triadBuffer;

	int32 m_groupCount;
	b2ParticleGroup* m_groupList;

	float32 m_pressureStrength;
	float32 m_dampingStrength;
	float32 m_elasticStrength;
	float32 m_springStrength;
	float32 m_viscousStrength;
	float32 m_surfaceTensionStrengthA;
	float32 m_surfaceTensionStrengthB;
	float32 m_powderStrength;
	float32 m_ejectionStrength;
	float32 m_colorMixingStrength;

	b2World* m_world;
};

inline b2ParticleGroup* b2ParticleSystem::GetParticleGroupList()
{
	return m_groupList;
}

inline const b2ParticleGroup* b2ParticleSystem::GetParticleGroupList() const
{
	return m_groupList;
}

inline int32 b2ParticleSystem::GetParticleGroupCount() const
{
	return m_groupCount;
}

inline int32 b2ParticleSystem::GetParticleCount() const
{
	return m_count;
}

#endif