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: $
//
//=============================================================================//
#include "simple_physics.h"
#include "tier0/dbg.h"
// memdbgon must be the last include file in a .cpp file!!!
#include "tier0/memdbgon.h"
CSimplePhysics::CSimplePhysics()
{
Init( 1.0f / 30.0f ); // default is 30 steps per second
}
void CSimplePhysics::Init( float flTimeStep )
{
m_flPredictedTime = 0;
m_iCurTimeStep = 0;
m_flTimeStep = flTimeStep;
m_flTimeStepMul = m_flTimeStep*m_flTimeStep*0.5f;
}
void CSimplePhysics::Simulate(
CSimplePhysics::CNode *pNodes,
int nNodes,
CSimplePhysics::IHelper *pHelper,
float dt,
float flDamp )
{
// Figure out how many time steps to run.
m_flPredictedTime += dt;
int newTimeStep = (int)ceil( m_flPredictedTime / m_flTimeStep );
int nTimeSteps = newTimeStep - m_iCurTimeStep;
for( int iTimeStep=0; iTimeStep < nTimeSteps; iTimeStep++ )
{
// Simulate everything..
for( int iNode=0; iNode < nNodes; iNode++ )
{
CSimplePhysics::CNode *pNode = &pNodes[iNode];
// Apply forces.
Vector vAccel;
pHelper->GetNodeForces( pNodes, iNode, &vAccel );
Assert( vAccel.IsValid() );
Vector vPrevPos = pNode->m_vPos;
pNode->m_vPos = pNode->m_vPos + (pNode->m_vPos - pNode->m_vPrevPos) * flDamp + vAccel * m_flTimeStepMul;
pNode->m_vPrevPos = vPrevPos;
}
// Apply constraints.
pHelper->ApplyConstraints( pNodes, nNodes );
}
m_iCurTimeStep = newTimeStep;
// Setup predicted positions.
float flInterpolant = (m_flPredictedTime - (GetCurTime() - m_flTimeStep)) / m_flTimeStep;
for( int iNode=0; iNode < nNodes; iNode++ )
{
CSimplePhysics::CNode *pNode = &pNodes[iNode];
VectorLerp( pNode->m_vPrevPos, pNode->m_vPos, flInterpolant, pNode->m_vPredicted );
}
}