RackAndPinionConstraint.h

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// Jolt Physics Library (https://github.com/jrouwe/JoltPhysics)
// SPDX-FileCopyrightText: 2021 Jorrit Rouwe
// SPDX-License-Identifier: MIT
 
#pragma once
 
#include <Jolt/Physics/Constraints/TwoBodyConstraint.h>
#include <Jolt/Physics/Constraints/ConstraintPart/RackAndPinionConstraintPart.h>
 
JPH_NAMESPACE_BEGIN
 
class RackAndPinionConstraintSettings final : public TwoBodyConstraintSettings
{
public:
    JPH_DECLARE_SERIALIZABLE_VIRTUAL(RackAndPinionConstraintSettings)
 
    // See: ConstraintSettings::SaveBinaryState
    virtual void                SaveBinaryState(StreamOut &inStream) const override;
 
    virtual TwoBodyConstraint * Create(Body &inBody1, Body &inBody2) const override;
 
    void                        SetRatio(int inNumTeethRack, float inRackLength, int inNumTeethPinion)
    {
        mRatio = 2.0f * JPH_PI * inNumTeethRack / (inRackLength * inNumTeethPinion);
    }
 
    EConstraintSpace            mSpace = EConstraintSpace::WorldSpace;
 
    Vec3                        mHingeAxis = Vec3::sAxisX();
    
    Vec3                        mSliderAxis = Vec3::sAxisX();
 
    float                       mRatio = 1.0f;
 
protected:
    // See: ConstraintSettings::RestoreBinaryState
    virtual void                RestoreBinaryState(StreamIn &inStream) override;
};
 
class RackAndPinionConstraint final : public TwoBodyConstraint
{
public:
    JPH_OVERRIDE_NEW_DELETE
 
                                RackAndPinionConstraint(Body &inBody1, Body &inBody2, const RackAndPinionConstraintSettings &inSettings);
 
    // Generic interface of a constraint
    virtual EConstraintSubType  GetSubType() const override                                             { return EConstraintSubType::RackAndPinion; }
    virtual void                NotifyShapeChanged(const BodyID &inBodyID, Vec3Arg inDeltaCOM) override { /* Nothing */ }
    virtual void                SetupVelocityConstraint(float inDeltaTime) override;
    virtual void                WarmStartVelocityConstraint(float inWarmStartImpulseRatio) override;
    virtual bool                SolveVelocityConstraint(float inDeltaTime) override;
    virtual bool                SolvePositionConstraint(float inDeltaTime, float inBaumgarte) override;
#ifdef JPH_DEBUG_RENDERER
    virtual void                DrawConstraint(DebugRenderer *inRenderer) const override;
#endif // JPH_DEBUG_RENDERER
    virtual void                SaveState(StateRecorder &inStream) const override;
    virtual void                RestoreState(StateRecorder &inStream) override;
    virtual Ref<ConstraintSettings> GetConstraintSettings() const override;
 
    // See: TwoBodyConstraint
    virtual Mat44               GetConstraintToBody1Matrix() const override;
    virtual Mat44               GetConstraintToBody2Matrix() const override;
 
    void                        SetConstraints(const Constraint *inPinion, const Constraint *inRack)    { mPinionConstraint = inPinion; mRackConstraint = inRack; }
 
    inline float                GetTotalLambda() const                                                  { return mRackAndPinionConstraintPart.GetTotalLambda(); }
 
private:
    // Internal helper function to calculate the values below
    void                        CalculateConstraintProperties(Mat44Arg inRotation1, Mat44Arg inRotation2);
 
    // CONFIGURATION PROPERTIES FOLLOW
 
    // Local space hinge axis
    Vec3                        mLocalSpaceHingeAxis;
 
    // Local space sliding direction
    Vec3                        mLocalSpaceSliderAxis;
 
    // Ratio between rack and pinion
    float                       mRatio;
 
    // The constraints that constrain the rack and pinion (a slider and a hinge), optional and used to calculate the position error and fix numerical drift.
    RefConst<Constraint>        mPinionConstraint;
    RefConst<Constraint>        mRackConstraint;
 
    // RUN TIME PROPERTIES FOLLOW
 
    // World space hinge axis
    Vec3                        mWorldSpaceHingeAxis;
 
    // World space sliding direction
    Vec3                        mWorldSpaceSliderAxis;
 
    // The constraint parts
    RackAndPinionConstraintPart mRackAndPinionConstraintPart;
};
 
JPH_NAMESPACE_END