find_path: consider walkable instead of CONTENT_AIR

The path finding code works fairly well except that it considers
anythin not CONTENT_AIR to be "above the surface". This results in
paths that are unwalkable for entities since e.g. plants are not
walkable. The path would force them to jump on top of grass plants,
etc..

The obvious solution is not to use CONTENT_AIR as a criteria, but
instead distinguish between walkable and non-walkable nodes. This
results in paths that properly walk through grass nodes.

This was extensively tested by a flock of electric sheep.

Note that for underwater purposes this changes the behaviour from
"the surface is walkable" to "ignore water entirely" making the
path go across the water bottom, and pathing fail likely from the
water surface. This is intentional.

1 files changed, 12 insertions, 9 deletions

diff --git a/src/pathfinder.cpp b/src/pathfinder.cpp
index cfbadd1e5..57a008ead 100644
--- a/src/pathfinder.cpp
+++ b/src/pathfinder.cpp
@@ -24,6 +24,8 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 
 #include "pathfinder.h"
 #include "environment.h"
+#include "gamedef.h"
+#include "nodedef.h"
 #include "map.h"
 #include "log.h"
 #include "irr_aabb3d.h"
@@ -518,6 +520,7 @@ void PathGridnode::setCost(v3s16 dir, PathCost cost)
 
 void GridNodeContainer::initNode(v3s16 ipos, PathGridnode *p_node)
 {
+	INodeDefManager *ndef = m_pathf->m_env->getGameDef()->ndef();
 	PathGridnode &elem = *p_node;
 
 	v3s16 realpos = m_pathf->getRealPos(ipos);
@@ -538,11 +541,10 @@ void GridNodeContainer::initNode(v3s16 ipos, PathGridnode *p_node)
 	}
 
 	//don't add anything if it isn't an air node
-	if ((current.param0 != CONTENT_AIR) ||
-				(below.param0 == CONTENT_AIR )) {
+	if (ndef->get(current).walkable || !ndef->get(below).walkable) {
 			DEBUG_OUT("Pathfinder: " << PPOS(realpos)
 				<< " not on surface" << std::endl);
-			if (current.param0 != CONTENT_AIR) {
+			if (ndef->get(current).walkable) {
 				elem.type = 's';
 				DEBUG_OUT(PPOS(ipos) << ": " << 's' << std::endl);
 			} else {
@@ -798,6 +800,7 @@ v3s16 Pathfinder::getRealPos(v3s16 ipos)
 /******************************************************************************/
 PathCost Pathfinder::calcCost(v3s16 pos, v3s16 dir)
 {
+	INodeDefManager *ndef = m_env->getGameDef()->ndef();
 	PathCost retval;
 
 	retval.updated = true;
@@ -820,7 +823,7 @@ PathCost Pathfinder::calcCost(v3s16 pos, v3s16 dir)
 			return retval;
 	}
 
-	if (node_at_pos2.param0 == CONTENT_AIR) {
+	if (!ndef->get(node_at_pos2).walkable) {
 		MapNode node_below_pos2 =
 							m_env->getMap().getNodeNoEx(pos2 + v3s16(0, -1, 0));
 
@@ -831,7 +834,7 @@ PathCost Pathfinder::calcCost(v3s16 pos, v3s16 dir)
 				return retval;
 		}
 
-		if (node_below_pos2.param0 != CONTENT_AIR) {
+		if (ndef->get(node_below_pos2).walkable) {
 			retval.valid = true;
 			retval.value = 1;
 			retval.direction = 0;
@@ -843,7 +846,7 @@ PathCost Pathfinder::calcCost(v3s16 pos, v3s16 dir)
 			MapNode node_at_pos = m_env->getMap().getNodeNoEx(testpos);
 
 			while ((node_at_pos.param0 != CONTENT_IGNORE) &&
-					(node_at_pos.param0 == CONTENT_AIR) &&
+					(!ndef->get(node_at_pos).walkable) &&
 					(testpos.Y > m_limits.MinEdge.Y)) {
 				testpos += v3s16(0, -1, 0);
 				node_at_pos = m_env->getMap().getNodeNoEx(testpos);
@@ -852,7 +855,7 @@ PathCost Pathfinder::calcCost(v3s16 pos, v3s16 dir)
 			//did we find surface?
 			if ((testpos.Y >= m_limits.MinEdge.Y) &&
 					(node_at_pos.param0 != CONTENT_IGNORE) &&
-					(node_at_pos.param0 != CONTENT_AIR)) {
+					(ndef->get(node_at_pos).walkable)) {
 				if ((pos2.Y - testpos.Y - 1) <= m_maxdrop) {
 					retval.valid = true;
 					retval.value = 2;
@@ -877,7 +880,7 @@ PathCost Pathfinder::calcCost(v3s16 pos, v3s16 dir)
 		MapNode node_at_pos = m_env->getMap().getNodeNoEx(testpos);
 
 		while ((node_at_pos.param0 != CONTENT_IGNORE) &&
-				(node_at_pos.param0 != CONTENT_AIR) &&
+				(ndef->get(node_at_pos).walkable) &&
 				(testpos.Y < m_limits.MaxEdge.Y)) {
 			testpos += v3s16(0, 1, 0);
 			node_at_pos = m_env->getMap().getNodeNoEx(testpos);
@@ -885,7 +888,7 @@ PathCost Pathfinder::calcCost(v3s16 pos, v3s16 dir)
 
 		//did we find surface?
 		if ((testpos.Y <= m_limits.MaxEdge.Y) &&
-				(node_at_pos.param0 == CONTENT_AIR)) {
+				(!ndef->get(node_at_pos).walkable)) {
 
 			if (testpos.Y - pos2.Y <= m_maxjump) {
 				retval.valid = true;