From 72c02ceb171949acd07338e77c8ee0d3439f8173 Mon Sep 17 00:00:00 2001
From: Christophe Piveteau <chripiveteau@gmail.com>
Date: Fri, 15 Aug 2014 17:54:43 +0200
Subject: Added a lot of comments

---
 src/Entities/Minecart.cpp | 66 ++++++++++++++++++++++++++---------------------
 1 file changed, 36 insertions(+), 30 deletions(-)

diff --git a/src/Entities/Minecart.cpp b/src/Entities/Minecart.cpp
index 4753f720d..9420eca02 100644
--- a/src/Entities/Minecart.cpp
+++ b/src/Entities/Minecart.cpp
@@ -876,7 +876,10 @@ bool cMinecart::TestEntityCollision(NIBBLETYPE a_RailMeta)
 			Vector3d Distance = MinecartCollisionCallback.GetCollidedEntityPosition() - Vector3d(GetPosX(), 0, GetPosZ());
 
 			// Prevent division by small numbers
-			Distance.z = std::max(Distance.z, 0.001);
+			if (abs(Distance.z) < 0.001)
+			{
+				Distance.z = 0.001;
+			}
 
 			/* Check to which side the minecart is to be pushed.
 			Let's consider a z-x-coordinate system where the minecart is the center (0/0).
@@ -886,27 +889,27 @@ bool cMinecart::TestEntityCollision(NIBBLETYPE a_RailMeta)
 				((Distance.z > 0) && ((Distance.x / Distance.z) >= 1)) ||
 				((Distance.z < 0) && ((Distance.x / Distance.z) <= 1))
 			)
-			{
-				if ((-GetSpeedX() * 0.4 / sqrt(2)) < 0.01)
-				{
+			{ // Moving -X + Z
+				if ((-GetSpeedX() * 0.4 / sqrt(2)) < 0.01) // ~ speedX >= 0
+				{ // Immobile or not moving in the "right" direction. Give it a bump!
 					AddSpeedX(-4 / sqrt(2));
 					AddSpeedZ(4 / sqrt(2));
 				}
-				else
-				{
-					SetSpeedX(-GetSpeedX() * 0.4);
-					SetSpeedZ(GetSpeedZ() * 0.4);
+				else // ~ SpeedX < 0
+				{ // Moving in the "right" direction. Only accelerate it a bit.
+					SetSpeedX(GetSpeedX() * 0.4 / sqrt(2));
+					SetSpeedZ(GetSpeedZ() * 0.4 / sqrt(2));
 				}
-			}
-			else if ((GetSpeedX() * 0.4 / sqrt(2)) < 0.01)
-			{
+			} // Moving +X -Z
+			else if ((GetSpeedX() * 0.4 / sqrt(2)) < 0.01) // ~ SpeedX <= 0
+			{ // Immobile or not moving in the "right" direction
 				AddSpeedX(4 / sqrt(2));
 				AddSpeedZ(-4 / sqrt(2));
 			}
-			else
-			{
-				SetSpeedX(GetSpeedX() * 0.4);
-				SetSpeedZ(-GetSpeedZ() * 0.4);
+			else // ~ SpeedX > 0
+			{ // Moving in the "right" direction
+				SetSpeedX(GetSpeedX() * 0.4 / sqrt(2));
+				SetSpeedZ(GetSpeedZ() * 0.4 / sqrt(2));
 			}
 			break;
 		}
@@ -916,37 +919,40 @@ bool cMinecart::TestEntityCollision(NIBBLETYPE a_RailMeta)
 			Vector3d Distance = MinecartCollisionCallback.GetCollidedEntityPosition() - Vector3d(GetPosX(), 0, GetPosZ());
 
 			// Prevent division by small numbers
-			Distance.z = std::max(Distance.z, 0.001);
+			if (abs(Distance.z) < 0.001)
+			{
+				Distance.z = 0.001;
+			}
 
 			/* Check to which side the minecart is to be pushed.
 			Let's consider a z-x-coordinate system where the minecart is the center (0/0).
 			The minecart moves along the line x = z, the perpendicular line to this is x = -z.
 			In order to decide to which side the minecart is to be pushed, it must be checked on what side of the perpendicular line the pushing entity is located. */
-			if (
+			if ( // Moving +X +Z
 				((Distance.z > 0) && ((Distance.x / Distance.z) <= -1)) ||
 				((Distance.z < 0) && ((Distance.x / Distance.z) >= -1))
 			)
 			{
-				if ((GetSpeedX() * 0.4) < 0.01)
-				{
+				if ((GetSpeedX() * 0.4) < 0.01) // ~ SpeedX <= 0
+				{ // Immobile or not moving in the "right" direction
 					AddSpeedX(4 / sqrt(2));
 					AddSpeedZ(4 / sqrt(2));
 				}
-				else
-				{
-					SetSpeedX(GetSpeedX() * 0.4);
-					SetSpeedZ(GetSpeedZ() * 0.4);
+				else // SpeedX > 0
+				{ // Moving in the "right" direction
+					SetSpeedX(GetSpeedX() * 0.4 / sqrt(2));
+					SetSpeedZ(GetSpeedZ() * 0.4 / sqrt(2));
 				}
-			}
-			else if ((-GetSpeedX() * 0.4) < 0.01)
-			{
+			} // Moving -X -Z
+			else if ((-GetSpeedX() * 0.4) < 0.01) // ~ SpeedX >= 0
+			{ // Immobile or not moving in the "right" direction
 				AddSpeedX(-4 / sqrt(2));
 				AddSpeedZ(-4 / sqrt(2));
 			}
-			else
-			{
-				SetSpeedX(-GetSpeedX() * 0.4);
-				SetSpeedZ(-GetSpeedZ() * 0.4);
+			else // ~ SpeedX < 0
+			{ // Moving in the "right" direction
+				SetSpeedX(GetSpeedX() * 0.4 / sqrt(2));
+				SetSpeedZ(GetSpeedZ() * 0.4 / sqrt(2));
 			}
 			break;
 		}
-- 
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