From 39ed87570bdb2f86969d4be821c94b722dc71179 Mon Sep 17 00:00:00 2001
From: Joe Ludwig <joe@valvesoftware.com>
Date: Wed, 26 Jun 2013 15:22:04 -0700
Subject: First version of the SOurce SDK 2013

---
 mp/src/public/simple_physics.cpp | 72 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 72 insertions(+)
 create mode 100644 mp/src/public/simple_physics.cpp

(limited to 'mp/src/public/simple_physics.cpp')

diff --git a/mp/src/public/simple_physics.cpp b/mp/src/public/simple_physics.cpp
new file mode 100644
index 00000000..d08c041d
--- /dev/null
+++ b/mp/src/public/simple_physics.cpp
@@ -0,0 +1,72 @@
+//========= 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 );
+	}
+}
+
+
-- 
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