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