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 "rope_physics.h"
#include "tier0/dbg.h"
// memdbgon must be the last include file in a .cpp file!!!
#include "tier0/memdbgon.h"
CBaseRopePhysics::CBaseRopePhysics( CSimplePhysics::CNode *pNodes, int nNodes, CRopeSpring *pSprings, float *flSpringDistsSqr )
{
m_pNodes = pNodes;
m_pSprings = pSprings;
m_flNodeSpringDistsSqr = flSpringDistsSqr;
m_flSpringDist = m_flSpringDistSqr = 1;
Restart();
// Initialize the nodes.
for ( int i=0; i < nNodes; i++ )
{
pNodes[i].m_vPos.Init();
pNodes[i].m_vPrevPos.Init();
pNodes[i].m_vPredicted.Init();
}
SetNumNodes( nNodes );
m_pDelegate = NULL;
}
void CBaseRopePhysics::SetNumNodes( int nNodes )
{
m_nNodes = nNodes;
// Setup the springs.
for( int i=0; i < NumSprings(); i++ )
{
m_pSprings[i].m_pNode1 = &m_pNodes[i].m_vPos;
m_pSprings[i].m_pNode2 = &m_pNodes[i+1].m_vPos;
Assert( m_pSprings[i].m_pNode1->IsValid() );
Assert( m_pSprings[i].m_pNode2->IsValid() );
m_flNodeSpringDistsSqr[i] = m_flSpringDistSqr / NumSprings();
}
}
void CBaseRopePhysics::Restart()
{
m_Physics.Init( 1.0 / 50 );
}
void CBaseRopePhysics::ResetSpringLength( float flSpringDist )
{
m_flSpringDist = max( flSpringDist, 0.f );
m_flSpringDistSqr = m_flSpringDist * m_flSpringDist;
for( int i=0; i < NumSprings(); i++ )
{
m_flNodeSpringDistsSqr[i] = m_flSpringDistSqr / NumSprings();
}
}
float CBaseRopePhysics::GetSpringLength() const
{
return m_flSpringDist;
}
void CBaseRopePhysics::ResetNodeSpringLength( int iStartNode, float flSpringDist )
{
m_flNodeSpringDistsSqr[iStartNode] = flSpringDist * flSpringDist;
}
void CBaseRopePhysics::SetupSimulation( float flSpringDist, CSimplePhysics::IHelper *pDelegate )
{
ResetSpringLength( flSpringDist );
SetDelegate( pDelegate );
}
void CBaseRopePhysics::SetDelegate( CSimplePhysics::IHelper *pDelegate )
{
m_pDelegate = pDelegate;
}
void CBaseRopePhysics::Simulate( float dt )
{
static float flEnergy = 0.98;
m_Physics.Simulate( m_pNodes, m_nNodes, this, dt, flEnergy );
}
void CBaseRopePhysics::GetNodeForces( CSimplePhysics::CNode *pNodes, int iNode, Vector *pAccel )
{
if( m_pDelegate )
m_pDelegate->GetNodeForces( pNodes, iNode, pAccel );
else
pAccel->Init( 0, 0, 0 );
}
void CBaseRopePhysics::ApplyConstraints( CSimplePhysics::CNode *pNodes, int nNodes )
{
// Handle springs..
//
// Iterate multiple times here. If we don't, then gravity tends to
// win over the constraint solver and it's impossible to get straight ropes.
static int nIterations = 3;
for( int iIteration=0; iIteration < nIterations; iIteration++ )
{
for( int i=0; i < NumSprings(); i++ )
{
CRopeSpring *s = &m_pSprings[i];
Vector vTo = *s->m_pNode1 - *s->m_pNode2;
float flDistSqr = vTo.LengthSqr();
// If we don't have an overall spring distance, see if we have a per-node one
float flSpringDist = m_flSpringDistSqr;
if ( !flSpringDist )
{
// TODO: This still isn't enough. Ropes with different spring lengths
// per-node will oscillate forever.
flSpringDist = m_flNodeSpringDistsSqr[i];
}
if( flDistSqr > flSpringDist )
{
float flDist = (float)sqrt( flDistSqr );
vTo *= 1 - (m_flSpringDist / flDist);
*s->m_pNode1 -= vTo * 0.5f;
*s->m_pNode2 += vTo * 0.5f;
}
}
if( m_pDelegate )
m_pDelegate->ApplyConstraints( pNodes, nNodes );
}
}