From ddaed2ad6951b212d44e5752b11c08dcf80c76c0 Mon Sep 17 00:00:00 2001
From: jacksonmj <mj-pt@jacksonmj.co.uk>
Date: Wed, 27 Apr 2011 19:02:27 +0100
Subject: [PATCH] Slight speed improvement for liquids and powders

---
 src/powder.c | 64 ++++++++++++++++++++++++++++++----------------------
 1 file changed, 37 insertions(+), 27 deletions(-)

diff --git a/src/powder.c b/src/powder.c
index 54d9e3dd2..533fc4962 100644
--- a/src/powder.c
+++ b/src/powder.c
@@ -1935,38 +1935,48 @@ killed:
 					}
 					else
 					{
+						s = 1;
 						r = (rand()%2)*2-1;
-						if (fin_y!=clear_y && try_move(i, x, y, clear_x+r, fin_y))
+						if (clear_x!=x || clear_y!=y || nt || surround_space)
 						{
-							parts[i].x = clear_xf+r;
-							parts[i].y = fin_yf;
-							parts[i].vx *= ptypes[t].collision;
-							parts[i].vy *= ptypes[t].collision;
+							// allow diagonal movement if target position is blocked
+							// but no point trying this if particle is stuck in a block of identical particles
+							if (fin_y!=clear_y && try_move(i, x, y, clear_x+r, fin_y))
+							{
+								parts[i].x = clear_xf+r;
+								parts[i].y = fin_yf;
+								parts[i].vx *= ptypes[t].collision;
+								parts[i].vy *= ptypes[t].collision;
+							}
+							else if (fin_y!=clear_y && try_move(i, x, y, clear_x-r, fin_y))
+							{
+								parts[i].x = clear_xf-r;
+								parts[i].y = fin_yf;
+								parts[i].vx *= ptypes[t].collision;
+								parts[i].vy *= ptypes[t].collision;
+							}
+							else if (fin_x!=clear_x && try_move(i, x, y, fin_x, clear_y+r))
+							{
+								parts[i].x = fin_xf;
+								parts[i].y = clear_yf+r;
+								parts[i].vx *= ptypes[t].collision;
+								parts[i].vy *= ptypes[t].collision;
+							}
+							else if (fin_x!=clear_x && try_move(i, x, y, fin_x, clear_y-r))
+							{
+								parts[i].x = fin_xf;
+								parts[i].y = clear_yf-r;
+								parts[i].vx *= ptypes[t].collision;
+								parts[i].vy *= ptypes[t].collision;
+							}
+							else s = 0;
 						}
-						else if (fin_y!=clear_y && try_move(i, x, y, clear_x-r, fin_y))
-						{
-							parts[i].x = clear_xf-r;
-							parts[i].y = fin_yf;
-							parts[i].vx *= ptypes[t].collision;
-							parts[i].vy *= ptypes[t].collision;
-						}
-						else if (fin_x!=clear_x && try_move(i, x, y, fin_x, clear_y+r))
-						{
-							parts[i].x = fin_xf;
-							parts[i].y = clear_yf+r;
-							parts[i].vx *= ptypes[t].collision;
-							parts[i].vy *= ptypes[t].collision;
-						}
-						else if (fin_x!=clear_x && try_move(i, x, y, fin_x, clear_y-r))
-						{
-							parts[i].x = fin_xf;
-							parts[i].y = clear_yf-r;
-							parts[i].vx *= ptypes[t].collision;
-							parts[i].vy *= ptypes[t].collision;
-						}
-						else if (ptypes[t].falldown>1 && (parts[i].vy>fabs(parts[i].vx) || gravityMode==2))
+						else s = 0;
+						// s==0 means particle has not yet moved, allow liquids code to run
+						if (s==0 && ptypes[t].falldown>1 && (parts[i].vy>fabs(parts[i].vx) || gravityMode==2))
 						{
 							s = 0;
+							// rt is true if FLAG_STAGNANT was set for this particle in previous frame
 							if (!rt || nt) //nt is if there is an something else besides the current particle type, around the particle
 								rt = 30;//slight less water lag, although it changes how it moves a lot
 							else