EngineSystem.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "Math/UnrealMathSSE.h"
#include "VehicleSystemTemplate.h"
#include "VehicleUtility.h"
 
#if VEHICLE_DEBUGGING_ENABLED
UE_DISABLE_OPTIMIZATION
#endif
 
 
namespace Chaos
{
 
    /*
     *  Simple Normally Aspirated Engine
     *  Output defined by a single torque curve over the rev range
     *  No turbo/ turbo lag
     *
     * #todo: proper default values
     * #todo: replace hardcoded graph with curve data
     */
 
    struct CHAOSVEHICLESCORE_API FSimpleEngineConfig
    {
        FSimpleEngineConfig()
            : MaxTorque(0.f)
            , MaxRPM(6000)
            , EngineIdleRPM(1200)
            , EngineBrakeEffect(0.2f)
            , EngineRevUpMOI(1.0f)
            , EngineRevDownRate(1.0f)
        {
            // #todo: do we want to provide a default torque curve, maybe even just a straight line
 
        }
 
        // #todo: want something like UCurveFloat / FRuntimeFloatCurve / FTorqueCurveEditor
        FNormalisedGraph TorqueCurve;
        float MaxTorque;            // [N.m] The peak torque Y value in the normalized torque graph
        uint16 MaxRPM;              // [RPM] The absolute maximum RPM the engine can theoretically reach (last X value in the normalized torque graph)
        uint16 EngineIdleRPM;       // [RPM] The RPM at which the throttle sits when the car is not moving          
        float EngineBrakeEffect;    // [0..1] How much the engine slows the vehicle when the throttle is released
 
        float EngineRevUpMOI;       // Affects speed at which engine RPM increases
        float EngineRevDownRate;        // Affects speed at which engine RPM decreases
 
    };
 
    class CHAOSVEHICLESCORE_API FSimpleEngineSim : public TVehicleSystem<FSimpleEngineConfig>
    {
    public:
 
        FSimpleEngineSim(const FSimpleEngineConfig* StaticDataIn);
 
        void StartEngine()
        {
            EngineStarted = true;
 
            // #todo: event for audio? perhaps a delay before you can drive off
        }
 
        void StopEngine()
        {
            EngineStarted = false;
 
            // #todo: event for audio? perhaps a delay before you can drive off
        }
 
        void SetThrottle(float InThrottle)
        {
            FVehicleUtility::ClampNormalRange(InThrottle);
            ThrottlePosition = InThrottle;
        }
 
        void SetEngineRPM(bool FreeRunningIn, float InEngineRPM)
        {
            FreeRunning = FreeRunningIn;
            if (!FreeRunning)
            {
                TargetSpeed = RPMToOmega(FMath::Clamp(FMath::Abs(InEngineRPM), (float)Setup().EngineIdleRPM, (float)Setup().MaxRPM));
            }
        }
 
        void SetMaxTorque(float InTorque)
        {
            MaxTorque = InTorque;
        }
 
        float GetEngineTorque()
        {
            if (EngineStarted)
            {
                return ThrottlePosition * GetTorqueFromRPM();
            }
 
            return 0.f;
        }
 
        float GetEngineRevRate()
        {
            return RevRate;
        }
 
        float GetTorqueFromRPM(bool LimitToIdle = true)
        {
            return GetTorqueFromRPM(CurrentRPM);
        }
 
        /* get torque value from torque curve based on input RPM */
        float GetTorqueFromRPM(float RPM, bool LimitToIdle = true);
 
 
        float GetEngineRPM() const
        {
            if (EngineStarted)
            {
                return CurrentRPM;
            }
 
            return 0.f;
        }
 
        float GetEngineOmega() const
        {
            return Omega;
        }
 
        void SetEngineOmega( const float EngineOmega)
        {
            Omega = EngineOmega;
        }
 
        void Simulate(float DeltaTime);
 
    protected:
        float MaxTorque;        // [N.m] The peak torque Y value in the normalized torque graph
        float ThrottlePosition; // [0..1 Normalized position]
        float TargetSpeed;      // target RPM
        float CurrentRPM;       // current RPM
        float DriveTorque;      // current torque [N.m]
 
        float EngineIdleSpeed;
        float MaxEngineSpeed;
        bool EngineStarted;     // is the engine turned off or has it been started
        bool FreeRunning;       // is engine in neutral with no load from the wheels/transmission
 
        float Omega;            // engine speed
        float RevRate;          // for debug rather than any practical purpose
 
    };
 
} // namespace Chaos
 
#if VEHICLE_DEBUGGING_ENABLED
UE_ENABLE_OPTIMIZATION
#endif