/*
* All or portions of this file Copyright (c) Amazon.com, Inc. or its affiliates or
* its licensors.
*
* For complete copyright and license terms please see the LICENSE at the root of this
* distribution (the "License"). All use of this software is governed by the License,
* or, if provided, by the license below or the license accompanying this file. Do not
* remove or modify any license notices. This file is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
*
*/
// Original file Copyright Crytek GMBH or its affiliates, used under license.

#ifndef CRYINCLUDE_CRYCOMMON_FORCE_H
#define CRYINCLUDE_CRYCOMMON_FORCE_H
#pragma once

/*
            F = force magnitude & dir
            C = force center
            s = object affinity
            P,P',P" = object position, velocity, accel

        Force types:

            Constant (gravity): Force on object
                P" = F s
                P' = P0' + F t
                P  = P0 + P0' t + F/2 t^2
                Directions: constant, point (f = 1/r^2 - 1/R^2), line (f = 1/r - 1/R)

            Flow (wind): Attracts velocity asymtotically to flow
                P" = (F-P') s
                P' = (P0'-F) e^(-s t) + F
                P  = P0 + (P0'-F)/s (1 - e^(-s t)) + F t
                Directions: constant, point, line, plane, vortex line ??

            Barrier: Halts approaching objects asymtotically
                In force space (C = 0),
                P" = (-P' * (P-C)) (P-C) / |P-C|^3
                P = P0 + P0'/s (1 - e^(-s t)),  s = P0'/(C-P0)
                P = P0 + (C-P0) (1 - e^(-P0'/(C-P0) t))
                Directions: plane, line, point (acts on parallel component)

            Hard attractor: Applies a variable force, forcing object to reach target
                Speed-preserving: applies perpendicular forces to simply turn objects w/o magnitude acceleration
                    Force is sufficient to let object reach target when it would have passed it at closest point
                Time limit:

                    P = P0 + P0' T + P"/2 T^2 = 0
                    P" = (-P0 - P0' T) 2/T^2

*/

struct ForceObject
{
    enum EForceType
    {
        eF_Attract,                         // x'' = F c
        eF_Target,                          // x'' = 2 x'^2 (x-C).p / (x-C).t^2
        eF_Flow,                                // x'' = (F-x') c
        eF_Barrier,                         // x'' = -(x'*F) / (x*F)
    };
    EForceType eType;
    enum EForceAffinity
    {
        eA_All,
        eA_Mass,
        eA_Drag,
    };
    EForceAffinity eAffinity;
    enum EGeometry
    {
        eG_Point,
        eG_Line,
        eG_Plane,
        eG_Volume,
    };
    EGeometry eGeometry;
    float       fInnerRadius;       // Fractional radius of max strength;

    float       fStrength;          // Const,Flow only
    QuatTS  qLocation;          // Pos = trans, Dir = Y axis, Radius = scale

    AUTO_STRUCT_INFO
};


#endif // CRYINCLUDE_CRYCOMMON_FORCE_H