From 8798c529d2505885f921c0422bb3a3314d2fe058 Mon Sep 17 00:00:00 2001
From: "madmaxoft@gmail.com"
 <madmaxoft@gmail.com@0a769ca7-a7f5-676a-18bf-c427514a06d6>
Date: Sun, 6 Jan 2013 19:32:40 +0000
Subject: [PATCH] Fixed disappearing pickups - wrong physics simulation.

FS #285

git-svn-id: http://mc-server.googlecode.com/svn/trunk@1125 0a769ca7-a7f5-676a-18bf-c427514a06d6
---
 source/Pickup.cpp | 68 +++++++++++++++++++++++++++--------------------
 1 file changed, 39 insertions(+), 29 deletions(-)

diff --git a/source/Pickup.cpp b/source/Pickup.cpp
index b2290ab73..1dce2f2ea 100644
--- a/source/Pickup.cpp
+++ b/source/Pickup.cpp
@@ -102,19 +102,20 @@ void cPickup::HandlePhysics(float a_Dt)
 {
 	m_ResultingSpeed.Set(0.f, 0.f, 0.f);
 	cWorld * World = GetWorld();
+	
+	a_Dt /= 1000;  // Go from msec to sec, so that physics formulas work
 
-	if( m_bOnGround ) // check if it's still on the ground
+	if (m_bOnGround) // check if it's still on the ground
 	{
-		int BlockX = (m_Pos.x)<0 ? (int)m_Pos.x-1 : (int)m_Pos.x;
-		int BlockZ = (m_Pos.z)<0 ? (int)m_Pos.z-1 : (int)m_Pos.z;
-		char BlockBelow = World->GetBlock( BlockX, (int)m_Pos.y -1, BlockZ );
-		//Not only air, falls through water ;)
-		if( BlockBelow == E_BLOCK_AIR || IsBlockWater(BlockBelow))
+		int BlockX = (m_Pos.x < 0) ? (int)m_Pos.x - 1 : (int)m_Pos.x;
+		int BlockZ = (m_Pos.z < 0) ? (int)m_Pos.z - 1 : (int)m_Pos.z;
+		char BlockBelow = World->GetBlock(BlockX, (int)m_Pos.y - 1, BlockZ);
+		if (BlockBelow == E_BLOCK_AIR || IsBlockWater(BlockBelow))
 		{
 			m_bOnGround = false;
 		}
-		char Block = World->GetBlock( BlockX, (int)m_Pos.y - (int)m_bOnGround, BlockZ );
-		char BlockIn = World->GetBlock( BlockX, (int)m_Pos.y, BlockZ );
+		char Block = World->GetBlock(BlockX, (int)m_Pos.y - (int)m_bOnGround, BlockZ );
+		char BlockIn = World->GetBlock(BlockX, (int)m_Pos.y, BlockZ );
 
 		if( IsBlockLava(Block) || Block == E_BLOCK_FIRE
 			|| IsBlockLava(BlockIn) || BlockIn == E_BLOCK_FIRE)
@@ -130,10 +131,10 @@ void cPickup::HandlePhysics(float a_Dt)
 			m_Pos.y += 0.2;
 			m_bReplicated = false;
 		}
-		m_Speed.x *= 0.7f/(1+a_Dt);
-		if( fabs(m_Speed.x) < 0.05 ) m_Speed.x = 0;
-		m_Speed.z *= 0.7f/(1+a_Dt);
-		if( fabs(m_Speed.z) < 0.05 ) m_Speed.z = 0;
+		m_Speed.x *= 0.7f / (1 + a_Dt);
+		if (fabs(m_Speed.x) < 0.05) m_Speed.x = 0;
+		m_Speed.z *= 0.7f / (1 + a_Dt);
+		if (fabs(m_Speed.z) < 0.05) m_Speed.z = 0;
 	}
 
 	// get flowing direction
@@ -165,34 +166,43 @@ void cPickup::HandlePhysics(float a_Dt)
 	}
 
 	m_ResultingSpeed += m_WaterSpeed;
-	
 
-	if( !m_bOnGround )
+	if (!m_bOnGround)
 	{
 
-		float Gravity = -9.81f*a_Dt;
+		float Gravity = -9.81f * a_Dt;
+		if (Gravity < -3)  // Cap gravity-caused speed at 3 m / sec
+		{
+			Gravity = -3;
+		}
 		m_Speed.y += Gravity;
 
 		// Set to hit position
 		m_ResultingSpeed += m_Speed;
+		
+		/*
+		LOGD("Pickup #%d speed: {%.03f, %.03f, %.03f}, pos {%.02f, %.02f, %.02f}", 
+			m_UniqueID,
+			m_ResultingSpeed.x, m_ResultingSpeed.y, m_ResultingSpeed.z,
+			m_Pos.x, m_Pos.y, m_Pos.z
+		);
+		*/
 
-		cTracer Tracer( GetWorld() );
-		int Ret = Tracer.Trace( m_Pos, m_Speed, 2 );
-		if( Ret ) // Oh noez! we hit something
+		cTracer Tracer(GetWorld());
+		int Ret = Tracer.Trace(m_Pos, m_Speed, 2);
+		if (Ret) // Oh noez! we hit something
 		{
-			
-
-			if( (Tracer.RealHit - Vector3f(m_Pos)).SqrLength() <= ( m_ResultingSpeed * a_Dt ).SqrLength() )
+			if ((Tracer.RealHit - Vector3f(m_Pos)).SqrLength() <= ( m_ResultingSpeed * a_Dt ).SqrLength())
 			{
 				m_bReplicated = false; // It's only interesting to replicate when we actually hit something...
-				if( Ret == 1 )
+				if (Ret == 1)
 				{
 
-					if( Tracer.HitNormal.x != 0.f ) m_Speed.x = 0.f;
-					if( Tracer.HitNormal.y != 0.f ) m_Speed.y = 0.f;
-					if( Tracer.HitNormal.z != 0.f ) m_Speed.z = 0.f;
+					if (Tracer.HitNormal.x != 0.f ) m_Speed.x = 0.f;
+					if (Tracer.HitNormal.y != 0.f ) m_Speed.y = 0.f;
+					if (Tracer.HitNormal.z != 0.f ) m_Speed.z = 0.f;
 
-					if( Tracer.HitNormal.y > 0 ) // means on ground
+					if (Tracer.HitNormal.y > 0) // means on ground
 					{
 						m_bOnGround = true;
 					}
@@ -202,15 +212,15 @@ void cPickup::HandlePhysics(float a_Dt)
 
 			}
 			else
-				m_Pos += m_ResultingSpeed*a_Dt;
+				m_Pos += m_ResultingSpeed * a_Dt;
 		}
 		else
 		{	// We didn't hit anything, so move =]
 			m_Pos += m_ResultingSpeed * a_Dt;
 		}
 	}
-	//Usable for debugging
-	//SetPosition(m_Pos.x, m_Pos.y, m_Pos.z);
+	// Usable for debugging
+	SetPosition(m_Pos.x, m_Pos.y, m_Pos.z);
 }