b2_rope.h

// MIT License
 
// Copyright (c) 2019 Erin Catto
 
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
 
// The above copyright notice and this permission notice shall be included in all
// copies or substantial portions of the Software.
 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
// SOFTWARE.
 
#ifndef B2_ROPE_H
#define B2_ROPE_H
 
#include "b2_api.h"
#include "b2_math.h"
 
class b2Draw;
struct b2RopeStretch;
struct b2RopeBend;
 
enum b2StretchingModel
{
    b2_pbdStretchingModel,
    b2_xpbdStretchingModel
};
 
enum b2BendingModel
{
    b2_springAngleBendingModel = 0,
    b2_pbdAngleBendingModel,
    b2_xpbdAngleBendingModel,
    b2_pbdDistanceBendingModel,
    b2_pbdHeightBendingModel,
    b2_pbdTriangleBendingModel
};
 
struct B2_API b2RopeTuning
{
    b2RopeTuning()
    {
        stretchingModel = b2_pbdStretchingModel;
        bendingModel = b2_pbdAngleBendingModel;
        damping = 0.0f;
        stretchStiffness = 1.0f;
        bendStiffness = 0.5f;
        bendHertz = 1.0f;
        bendDamping = 0.0f;
        isometric = false;
        fixedEffectiveMass = false;
        warmStart = false;
    }
 
    b2StretchingModel stretchingModel;
    b2BendingModel bendingModel;
    float damping;
    float stretchStiffness;
    float stretchHertz;
    float stretchDamping;
    float bendStiffness;
    float bendHertz;
    float bendDamping;
    bool isometric;
    bool fixedEffectiveMass;
    bool warmStart;
};
 
struct B2_API b2RopeDef
{
    b2RopeDef()
    {
        position.SetZero();
        vertices = nullptr;
        count = 0;
        masses = nullptr;
        gravity.SetZero();
    }
 
    b2Vec2 position;
    b2Vec2* vertices;
    int32 count;
    float* masses;
    b2Vec2 gravity;
    b2RopeTuning tuning;
};
 
class B2_API b2Rope
{
public:
    b2Rope();
    ~b2Rope();
 
    void Create(const b2RopeDef& def);
 
    void SetTuning(const b2RopeTuning& tuning);
 
    void Step(float timeStep, int32 iterations, const b2Vec2& position);
 
    void Reset(const b2Vec2& position);
 
    void Draw(b2Draw* draw) const;
 
private:
 
    void SolveStretch_PBD();
    void SolveStretch_XPBD(float dt);
    void SolveBend_PBD_Angle();
    void SolveBend_XPBD_Angle(float dt);
    void SolveBend_PBD_Distance();
    void SolveBend_PBD_Height();
    void SolveBend_PBD_Triangle();
    void ApplyBendForces(float dt);
 
    b2Vec2 m_position;
 
    int32 m_count;
    int32 m_stretchCount;
    int32 m_bendCount;
 
    b2RopeStretch* m_stretchConstraints;
    b2RopeBend* m_bendConstraints;
 
    b2Vec2* m_bindPositions;
    b2Vec2* m_ps;
    b2Vec2* m_p0s;
    b2Vec2* m_vs;
 
    float* m_invMasses;
    b2Vec2 m_gravity;
 
    b2RopeTuning m_tuning;
};
 
#endif