Index: common/cmodel.c
===================================================================
--- common/cmodel.c	(revision 15647)
+++ common/cmodel.c	(working copy)
@@ -122,7 +122,7 @@
 } mapTile_t;
 
 /**
- * @brief Pathfinding routing structure
+ * @brief Pathfinding routing structure and tile layout
  * @note Comments strongly WIP!
  *
  * ROUTE
@@ -159,6 +159,17 @@
  * AREASTORED
  * 	The stored mask (the cached move) of the routing data. (See Grid_MoveLength)
  *
+ * TILE LAYOUT AND PATHING
+ *  Maps are comprised of tiles.  Each tile has a number of levels corresponding to entities in game.
+ *  All static entities in the tile are located in levels 0-255, with the main world located in 0.
+ *  Levels 256-258 are reserved, see LEVEL_* constants in src/shared/shared.h.  Non-static entities
+ *  (ET_BREAKABLE and ET_ROTATING, ET_DOOR, etc.) are contained in levels 259 and above. These entities'
+ *  models are named *##, beginning from 1, and each corresponds to level LEVEL_STEPON + ##.
+ *
+ *  The code that handles the pathing has separate checks for the static and non-static levels in a tile.
+ *  The static levels have their bounds precalculated by CM_MakeTracingNodes and stored in tile->theads.
+ *  The other levels are checked in the fly when Grid_CheckUnit is called.
+ *
  */
 typedef struct routing_s {
 	byte route[PATHFINDING_HEIGHT][PATHFINDING_WIDTH][PATHFINDING_WIDTH];
@@ -803,9 +814,14 @@
 	/* get step height and trace vectors */
 	sh = R_STEP(map, x, y, z) ? sh_big : sh_low;
 	h = R_HEIGHT(map, x, y, z);
+
+	/* Setup the points used to check for walls and such */
 	VectorSet(pos, x, y, z);
 	PosToVec(pos, start);
-	start[2] += h * 4;
+	/* Adjust height to the actual floor height. */
+	start[2] += h * QUANT;
+	/* Set the end point to the edge of the field unit in the direction traveling */
+	/** @todo: should this check into the center of the adjacent field unit insead of just to the edge? */
 	VectorSet(end, start[0] + (UNIT_HEIGHT / 2) * dvecs[dir][0], start[1] + (UNIT_HEIGHT / 2) * dvecs[dir][1], start[2]);
 
 	ax = x + dvecs[dir][0];
@@ -831,12 +847,13 @@
 	if (R_HEIGHT(map, ax, ay, az) > h)
 		return;
 
+	/** @todo: Do we need to use a bounding box to check for things in the way of this move? */
 	/* center check */
 	if (CM_EntTestLine(start, end))
 		return;
 
 	/* lower check */
-	start[2] = end[2] -= UNIT_HEIGHT / 2 - sh * 4 - 2;
+	start[2] = end[2] -= UNIT_HEIGHT / 2 - sh * QUANT - 2;
 	if (CM_EntTestLine(start, end))
 		return;
 
@@ -1157,7 +1174,7 @@
 	if (l->filelen + 1 > MAX_MAP_ENTSTRING)
 		Com_Error(ERR_DROP, "CMod_LoadEntityString: Map has too large entity lump");
 
-	/* marge entitystring information */
+	/* merge entitystring information */
 	es = (char *) (cmod_base + l->fileofs);
 	while (1) {
 		/* parse the opening brace */
@@ -1734,6 +1751,8 @@
 
 /**
  * @sa CM_ClipBoxToBrush
+ * @sa CM_TestBoxInBrush
+ * @sa CM_RecursiveHullCheck
  */
 static void CM_TraceToLeaf (int leafnum)
 {
@@ -2855,8 +2874,11 @@
 		y = pos[1] - dy;
 		z = sz;
 
-		/** @todo: What exactly is checked here? Exact description wanted/needed. */
-		if (R_AREA(map, x, y, z) != (l - TU_MOVE_STRAIGHT) - (dir > 3))
+		/**
+		 * This code verifies the TE table. If the table does not match the movement calculation,
+		 * we skip this invalid comparison.
+		*/
+		if (R_AREA(map, x, y, z) != l - ((dir > 3) ? TU_MOVE_DIAGONAL : TU_MOVE_STRAIGHT))
 			continue;
 
 		/* connection checks */
@@ -2922,7 +2944,7 @@
 	}
 
 	/* shouldn't happen */
-	Com_Printf("failed...\n");
+	Com_Printf("Grid_MoveNext failed...\n");
 	/* ROUTING_NOT_REACHABLE means, not possible/reachable */
 	return ROUTING_NOT_REACHABLE;
 }
Index: game/g_func.c
===================================================================
--- game/g_func.c	(revision 15647)
+++ game/g_func.c	(working copy)
@@ -32,6 +32,17 @@
 /**
  * @brief QUAKED func_breakable (0.3 0.3 0.3) ?
  * Used for breakable objects.
+ * SPAWNFLAGS bit values:
+ *  0x0001 Visible from layer 1
+ *  0x0002 Visible from layer 2
+ *  0x0004 Visible from layer 3
+ *  0x0008 Visible from layer 4
+ *  0x0010 Visible from layer 5
+ *  0x0020 Visible from layer 6
+ *  0x0040 Visible from layer 7
+ *  0x0080 Visible from layer 8
+ *  0x0100 Not present during day (defined in src/client/cl_view.c)
+ *  0x0200 Glows (defined in src/client/cl_view.c)
  * @note These edicts are added client side as local models
  * the are stored in the lmList (because they are inline models)
  * for tracing (see inlineList in cmodel.c)
Index: game/q_shared.h
===================================================================
--- game/q_shared.h	(revision 15647)
+++ game/q_shared.h	(working copy)
@@ -136,7 +136,7 @@
 #define GROUND_DELTA        28
 /* player height - 12 to be able to walk trough doors
  * UNIT_HEIGHT is the height of one level */
-#define PLAYER_HEIGHT		(UNIT_HEIGHT-12)
+#define PLAYER_HEIGHT		(UNIT_HEIGHT - 16)
 
 /* LINKED LIST STUFF */
 
Index: tools/ufo2map/bsp.c
===================================================================
--- tools/ufo2map/bsp.c	(revision 15647)
+++ tools/ufo2map/bsp.c	(working copy)
@@ -76,7 +76,7 @@
 		list = ChopBrushes(list);
 	tree = BrushBSP(list, mins, maxs);
 	if (tree->headnode->planenum == PLANENUM_LEAF)
-		Sys_Error("No head node bmodel of %s\n", ValueForKey(e, "classname"));
+		Sys_Error("No head node bmodel of %s (%i)\n", ValueForKey(e, "classname"), entityNum);
 	MakeTreePortals(tree);
 	MarkVisibleSides(tree, start, end);
 	MakeFaces(tree->headnode);
Index: tools/ufo2map/routing.c
===================================================================
--- tools/ufo2map/routing.c	(revision 15647)
+++ tools/ufo2map/routing.c	(working copy)
@@ -80,8 +80,8 @@
 
 	/* prepare fall down check */
 	VectorCopy(end, start);
-	start[2] -= UNIT_HEIGHT / 2 - 4;
-	end[2]   -= UNIT_HEIGHT / 2 + 4;
+	start[2] -= UNIT_HEIGHT / 2 - QUANT;
+	end[2]   -= UNIT_HEIGHT / 2 + QUANT;
 
 	/* FIXME: Don't allow falling over more than 1 level (z-direction) */
 	/* test for fall down */
@@ -190,6 +190,7 @@
 	/* prepare trace */
 	VectorSet(pos, x, y, z);
 	PosToVec(pos, start);
+	/* Adjust height to actual floor height. */
 	start[2] += h * QUANT;
 	VectorCopy(start, ts);
 
@@ -224,8 +225,8 @@
 			ay = y - 1;
 			break;
 		}
-		/* range check*/
-		if (x < 0 || x >= PATHFINDING_WIDTH || y < 0 || y >= PATHFINDING_WIDTH)
+		/* range check- ensure that ax and ay are on the map*/
+		if (ax < 0 || ax >= PATHFINDING_WIDTH || ay < 0 || ay >= PATHFINDING_WIDTH)
 			continue;
 		/* height check */
 		if ((route[sz][ay][ax] & 0x0F) > h)
@@ -237,7 +238,7 @@
 		if ((fall[ay][ax] & deep_fall[sz]) == deep_fall[sz])
 			continue;
 
-		/* test for walls */
+		/* Create the end point of the line to test. */
 		VectorAdd(start, move_vec[i], te);
 
 		/* center check */