Bounds check before interpolation to find walls

src/simulation/Air.cpp

@@ -235,17 +235,9 @@ void Air::update_air(void)
 							dp += pv[y][x]*f;
 						}
 
-				if (dx*advDistanceMult<=1.0f && dy*advDistanceMult<=1.0f)
-				{
-					tx = x - dx*advDistanceMult;
-					ty = y - dy*advDistanceMult;
-				}
-				else if (bmap_blockair[y][x])
-				{
-					tx = x;
-					ty = y;
-				}
-				else
+				tx = x - dx*advDistanceMult;
+				ty = y - dy*advDistanceMult;
+				if ((dx*advDistanceMult>1.0f || dy*advDistanceMult>1.0f) && (tx>=2 && tx<XRES/CELL-2 && ty>=2 && ty<YRES/CELL-2))
 				{
 					// Trying to take velocity from far away, check whether there is an intervening wall. Step from current position to desired source location, looking for walls, with either the x or y step size being 1 cell
 					if (abs(dx)>abs(dy))
@@ -284,8 +276,8 @@ void Air::update_air(void)
 				j = (int)ty;
 				tx -= i;
 				ty -= j;
-				if (i>=2 && i<XRES/CELL-3 &&
-				        j>=2 && j<YRES/CELL-3)
+				if (!bmap_blockair[y][x] && i>=2 && i<=XRES/CELL-3 &&
+				        j>=2 && j<=YRES/CELL-3)
 				{
 					dx *= 1.0f - AIR_VADV;
 					dy *= 1.0f - AIR_VADV;