ParticleEmitterType.h

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/* Copyright (C) 2022 Wildfire Games.
 * This file is part of 0 A.D.
 *
 * 0 A.D. is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) any later version.
 *
 * 0 A.D. is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with 0 A.D.  If not, see <http://www.gnu.org/licenses/>.
 */

#ifndef INCLUDED_PARTICLEEMITTERTYPE
#define INCLUDED_PARTICLEEMITTERTYPE

#include "graphics/Texture.h"
#include "lib/file/vfs/vfs_path.h"
#include "maths/BoundingBoxAligned.h"

#include <memory>
#include <string>

class CVector3D;
class CParticleEmitter;
class CParticleManager;
class IParticleVar;
class IParticleEffector;

/**
 * Particle emitter type - stores the common state data for all emitters of that
 * type, and uses that data to update the emitter states.
 *
 * The data is initialised from XML files.
 *
 * Most of the emitter type data is represented as subclasses of IParticleVar,
 * which will typically return a constant value or a random value each time it's
 * evaluated. New subclasses can be added to support different random distributions,
 * etc.
 */
class CParticleEmitterType
{
    NONCOPYABLE(CParticleEmitterType);  // reference member
public:
    CParticleEmitterType(const VfsPath& path, CParticleManager& manager);

private:
    friend class CModelParticleEmitter;
    friend class CParticleEmitter;
    friend class CParticleVarConstant;
    friend class CParticleVarUniform;
    friend class CParticleVarCopy;
    friend class ParticleRenderer;

    enum
    {
        VAR_EMISSIONRATE,
        VAR_LIFETIME,
        VAR_POSITION_X,
        VAR_POSITION_Y,
        VAR_POSITION_Z,
        VAR_ANGLE,
        VAR_VELOCITY_X,
        VAR_VELOCITY_Y,
        VAR_VELOCITY_Z,
        VAR_VELOCITY_ANGLE,
        VAR_SIZE,
        VAR_SIZE_GROWTHRATE,
        VAR_COLOR_R,
        VAR_COLOR_G,
        VAR_COLOR_B,
        VAR__MAX
    };

    enum class BlendMode
    {
        ADD,
        SUBTRACT,
        OVERLAY,
        MULTIPLY
    };

    int GetVariableID(const std::string& name);

    bool LoadXML(const VfsPath& path);

    /**
     * Update the state of an emitter's particles, by a potentially long time @p dt.
     */
    void UpdateEmitter(CParticleEmitter& emitter, float dt);

    /**
     * Update the state of an emitter's particles, by a short time @p dt that can
     * be computed in a single step.
     */
    void UpdateEmitterStep(CParticleEmitter& emitter, float dt);

    CBoundingBoxAligned CalculateBounds(CVector3D emitterPos, CBoundingBoxAligned emittedBounds);

    CTexturePtr m_Texture;

    BlendMode m_BlendMode = BlendMode::ADD;
    bool m_StartFull;
    bool m_UseRelativeVelocity;

    float m_MaxLifetime;
    u16 m_MaxParticles;
    CBoundingBoxAligned m_MaxBounds;

    typedef std::shared_ptr<IParticleVar> IParticleVarPtr;
    std::vector<IParticleVarPtr> m_Variables;

    typedef std::shared_ptr<IParticleEffector> IParticleEffectorPtr;
    std::vector<IParticleEffectorPtr> m_Effectors;

    CParticleManager& m_Manager;
};

typedef std::shared_ptr<CParticleEmitterType> CParticleEmitterTypePtr;

#endif // INCLUDED_PARTICLEEMITTERTYPE