From 6b90a1c8bb9efff7f660e352bf69a02992d620cc Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Thu, 21 Nov 2013 19:41:15 +0200
Subject: [PATCH] More efficient picking of terrain nodes

---
 source/libr2c2/terrain.cpp | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/source/libr2c2/terrain.cpp b/source/libr2c2/terrain.cpp
index e84c7cd..d4f3e41 100644
--- a/source/libr2c2/terrain.cpp
+++ b/source/libr2c2/terrain.cpp
@@ -132,6 +132,11 @@ Vector Terrain::get_node_position(const NodeCoordinates &c) const
 
 Terrain::NodeCoordinates Terrain::get_closest_node(const Ray &ray) const
 {
+	Transform reverse_trans = Transform::rotation(rotation, Vector(0, 0, -1))*
+		Transform::translation(-position);
+	Ray local_ray = reverse_trans.transform(ray);
+
+	float ts = type.get_tile_size();
 	NodeCoordinates coords;
 	float closest_dist = -1;
 	for(unsigned y=0; y<height; ++y)
@@ -139,17 +144,16 @@ Terrain::NodeCoordinates Terrain::get_closest_node(const Ray &ray) const
 			for(unsigned i=0; i<4; ++i)
 			{
 				NodeCoordinates c(x, y, i);
-				/* XXX This is not very efficient.  Should transform the ray to
-				local coordinate system. */
-				Vector node_pos = get_node_position(c);
-				Vector v = node_pos-ray.get_start();
-				float dist = (v-ray.get_direction()*dot(ray.get_direction(), v)).norm();
+				Vector node_pos((x+i%2)*ts, (y+i/2)*ts, get_node_elevation(c));
+				Vector v = node_pos-local_ray.get_start();
+				float dist = (v-local_ray.get_direction()*dot(local_ray.get_direction(), v)).norm();
 				if(closest_dist<0 || dist<closest_dist)
 				{
 					coords = c;
 					closest_dist = dist;
 				}
 			}
+
 	return coords;
 }
 
-- 
2.43.0