CCmpMotionBall.cpp

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/* Copyright (C) 2012 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/>.
 */

#include "precompiled.h"

#include "simulation2/system/Component.h"
#include "ICmpMotion.h"

#include "ICmpPosition.h"
#include "simulation2/MessageTypes.h"

#include "graphics/Terrain.h"

class CCmpMotionBall : public ICmpMotion
{
public:
    static void ClassInit(CComponentManager& componentManager)
    {
        componentManager.SubscribeToMessageType(MT_Update);
    }

    DEFAULT_COMPONENT_ALLOCATOR(MotionBall)

    // Current speed in metres per second
    float m_SpeedX, m_SpeedZ;

    static std::string GetSchema()
    {
        return "<a:component type='test'/><ref name='anything'/>";
    }

    virtual void Init(const CParamNode& UNUSED(paramNode))
    {
        m_SpeedX = 0;
        m_SpeedZ = 0;
    }

    virtual void Deinit()
    {
    }

    virtual void Serialize(ISerializer& serialize)
    {
        serialize.NumberFloat_Unbounded("speed x", m_SpeedX);
        serialize.NumberFloat_Unbounded("speed z", m_SpeedZ);
    }

    virtual void Deserialize(const CParamNode& paramNode, IDeserializer& deserialize)
    {
        Init(paramNode);
        deserialize.NumberFloat_Unbounded("speed x", m_SpeedX);
        deserialize.NumberFloat_Unbounded("speed z", m_SpeedZ);
    }

    virtual void HandleMessage(const CMessage& msg, bool UNUSED(global))
    {
        switch (msg.GetType())
        {
        case MT_Update:
        {
            fixed dt = static_cast<const CMessageUpdate&> (msg).turnLength;
            Move(dt);
            break;
        }
        }
    }

    void Move(fixed dt);
};

void CCmpMotionBall::Move(fixed dt)
{
    CmpPtr<ICmpPosition> cmpPosition(GetEntityHandle());
    if (!cmpPosition)
        return;

    // TODO: this is all FP-unsafe

    CFixedVector3D pos = cmpPosition->GetPosition();
    float x = pos.X.ToFloat();
    float z = pos.Z.ToFloat();

    CVector3D normal = GetSimContext().GetTerrain().CalcExactNormal(x, z);
    // Flatten the vector, to get the downhill force
    float g = 10.f;
    CVector3D force(g * normal.X, 0.f, g * normal.Z);

    m_SpeedX += force.X;
    m_SpeedZ += force.Z;

    float drag = 0.5f; // fractional decay per second

    float dt_ = dt.ToFloat();

    m_SpeedX *= powf(drag, dt_);
    m_SpeedZ *= powf(drag, dt_);

    cmpPosition->MoveTo(entity_pos_t::FromFloat(x + m_SpeedX * dt_), entity_pos_t::FromFloat(z + m_SpeedZ * dt_));
}

REGISTER_COMPONENT_TYPE(MotionBall)