Modified source engine (2017) developed by valve and leaked in 2020. Not for commercial purporses
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//========= Copyright Valve Corporation, All rights reserved. ============//
//
// Purpose:
//
// $NoKeywords: $
//=============================================================================//
#ifndef SIMPLE_PHYSICS_H
#define SIMPLE_PHYSICS_H
#ifdef _WIN32
#pragma once
#endif
#include "mathlib/vector.h"
// CSimplePhysics is a framework for simplified physics simulation.
// It simulates at a fixed timestep and uses the Verlet integrator.
//
// To use it, create your nodes and implement your constraints and
// forces in an IHelper, then call Simulate each frame.
// CSimplePhysics will figure out how many timesteps to run and will
// provide predicted positions of things for you.
class CSimplePhysics
{
public:
class CNode
{
public:
// Call this when initializing the nodes with their starting positions.
void Init( const Vector &vPos )
{
m_vPos = m_vPrevPos = m_vPredicted = vPos;
}
Vector m_vPos; // At time t
Vector m_vPrevPos; // At time t - m_flTimeStep
Vector m_vPredicted; // Predicted position
};
class IHelper
{
public:
virtual void GetNodeForces( CNode *pNodes, int iNode, Vector *pAccel ) = 0;
virtual void ApplyConstraints( CNode *pNodes, int nNodes ) = 0;
};
public:
CSimplePhysics();
void Init( float flTimeStep );
void Simulate(
CNode *pNodes,
int nNodes,
IHelper *pHelper,
float dt,
float flDamp );
private:
double GetCurTime() { return m_flTimeStep * m_iCurTimeStep; }
private:
double m_flPredictedTime; // (GetCurTime()-m_flTimeStep) <= m_flPredictedTime <= GetCurTime()
int m_iCurTimeStep;
float m_flTimeStep;
float m_flTimeStepMul; // dt*dt*0.5
};
#endif // SIMPLE_PHYSICS_H