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 "cbase.h"
#include "rope_helpers.h"
#include "basetypes.h"
#include "mathlib/mathlib.h"
#include "rope_shared.h"
#include "rope_physics.h"
#include "networkvar.h"
// memdbgon must be the last include file in a .cpp file!!!
#include "tier0/memdbgon.h"
class CHangRope : public CRopePhysics<512>
{
DECLARE_CLASS( CHangRope, CRopePhysics<512> );
// CRopePhysics overrides.
public:
virtual void GetNodeForces( CSimplePhysics::CNode *pNodes, int iNode, Vector *pAccel )
{
pAccel->Init( ROPE_GRAVITY );
}
virtual void ApplyConstraints( CSimplePhysics::CNode *pNodes, int nNodes )
{
// Apply spring forces.
BaseClass::ApplyConstraints( pNodes, nNodes );
// Lock the endpoints.
pNodes[0].m_vPos = m_vEndPoints[0];
pNodes[nNodes-1].m_vPos = m_vEndPoints[1];
// Calculate how far it is hanging down and adjust if necessary.
float flCurHangDist = 0;
for ( int i=0; i < NumNodes(); i++ )
{
float hang = fabs( m_flStartZ - GetNode(i)->m_vPos.z );
if ( hang > flCurHangDist )
flCurHangDist = hang;
}
// Adjust our spring length accordingly.
if ( flCurHangDist < m_flWantedHangDist )
m_flCurSlack += 1;
else
m_flCurSlack -= 1;
ApplyNewSpringLength();
}
// Helpers.
public:
void ApplyNewSpringLength()
{
ResetSpringLength( (m_flRopeLength + m_flCurSlack + ROPESLACK_FUDGEFACTOR) / (NumNodes() - 1) );
}
// Variables used to adjust the rope slack.
public:
Vector m_vEndPoints[2];
bool m_bAdjustSlack;
float m_flRopeLength;
float m_flCurSlack;
float m_flWantedHangDist;
float m_flStartZ;
};
void CalcRopeStartingConditions(
const Vector &vStartPos,
const Vector &vEndPos,
int const nNodes,
float const desiredHang,
float *pOutputLength,
float *pOutputSlack
)
{
CHangRope rope;
// Initialize the rope as a straight line with no slack as our first approximation.
// We then relax the rope by adding slack until it hangs to the desired height.
//
// The spring length equation is:
// springLength = (ropeLength + slack + ROPESLACK_FUDGEFACTOR) / (nNodes - 1)
//
// We want our rope to be a straight line, so:
// springLength = ropeLength / (nNodes-1)
//
// Therefore our initial slack is -ROPESLACK_FUDGEFACTOR
rope.m_flCurSlack = -ROPESLACK_FUDGEFACTOR;
rope.m_vEndPoints[0] = vStartPos;
rope.m_vEndPoints[1] = vEndPos;
rope.m_flRopeLength = (vEndPos - vStartPos).Length();
rope.m_flWantedHangDist = desiredHang;
rope.m_flStartZ = MIN( vStartPos.z, vEndPos.z ); // Calculate hang as the Z distance from the
// lowest endpoint to the bottom of the rope.
rope.SetNumNodes( nNodes );
// Set the node positions.
for ( int i=0; i < rope.NumNodes(); i++ )
{
CSimplePhysics::CNode *pNode = rope.GetNode( i );
float t = (float)i / (rope.NumNodes() - 1);
VectorLerp( vStartPos, vEndPos, t, pNode->m_vPos );
pNode->m_vPrevPos = pNode->m_vPos;
}
// Now simulate a little and stretch out to let it hang down.
rope.Restart();
rope.Simulate( 3 );
// Set outputs.
*pOutputLength = rope.m_flRopeLength;
*pOutputSlack = rope.m_flCurSlack;
}