From f6e6b6b7151af9290c0597acb1995ed157378529 Mon Sep 17 00:00:00 2001
From: Robert Vollmert <rvollmert@gmx.net>
Date: Fri, 16 Oct 2009 23:48:56 +0200
Subject: Rewrite cell_see_cell using exists_ray.

For this, add new opacity_func that disregards half-opaque things.
---
 crawl-ref/source/los.cc      |  8 ++------
 crawl-ref/source/losparam.cc |  8 ++++++++
 crawl-ref/source/losparam.h  | 14 +++++++++++---
 3 files changed, 21 insertions(+), 9 deletions(-)

(limited to 'crawl-ref')

diff --git a/crawl-ref/source/los.cc b/crawl-ref/source/los.cc
index 38de458419..9dbe3bc23d 100644
--- a/crawl-ref/source/los.cc
+++ b/crawl-ref/source/los.cc
@@ -775,14 +775,10 @@ int num_feats_between(const coord_def& source, const coord_def& target,
     return (count);
 }
 
-// Is p2 visible from p1, disregarding clouds?
-// XXX: Horribly inefficient since we do an entire LOS calculation;
-//      needs to be rewritten if it is used more.
+// Is p2 visible from p1, disregarding half-opaque objects?
 bool cell_see_cell(const coord_def& p1, const coord_def& p2)
 {
-    env_show_grid show;
-    losight(show, p1);
-    return see_grid(show, p1, p2);
+    return exists_ray(p1, p2, opc_fullyopaque);
 }
 
 // We use raycasting. The algorithm:
diff --git a/crawl-ref/source/losparam.cc b/crawl-ref/source/losparam.cc
index f24acf4551..132c2005f2 100644
--- a/crawl-ref/source/losparam.cc
+++ b/crawl-ref/source/losparam.cc
@@ -30,6 +30,14 @@ opacity_type opacity_default::operator()(const coord_def& p) const
         return OPC_CLEAR;
 }
 
+opacity_type opacity_fullyopaque::operator()(const coord_def& p) const
+{
+    if (grid_is_opaque(env.grid(p)))
+        return OPC_OPAQUE;
+    else
+        return OPC_CLEAR;
+}
+
 // Make anything solid block in addition to normal LOS.
 // XXX: Are trees, bushes solid?
 opacity_type opacity_solid::operator()(const coord_def& p) const
diff --git a/crawl-ref/source/losparam.h b/crawl-ref/source/losparam.h
index 505d0989ff..4d5bc141e1 100644
--- a/crawl-ref/source/losparam.h
+++ b/crawl-ref/source/losparam.h
@@ -34,7 +34,15 @@ struct opacity_default : opacity_func
 {
     opacity_type operator()(const coord_def& p) const;
 };
-static opacity_default opc_default = opacity_default();
+static opacity_default opc_default;
+
+// Default LOS rules, but only consider fully opaque features blocking.
+// In particular, clouds don't affect the result.
+struct opacity_fullyopaque : opacity_func
+{
+    opacity_type operator()(const coord_def& p) const;
+};
+static opacity_fullyopaque opc_fullyopaque;
 
 // Make anything solid block in addition to normal LOS.
 // XXX: Are trees, bushes solid?
@@ -42,7 +50,7 @@ struct opacity_solid : opacity_func
 {
     opacity_type operator()(const coord_def& p) const;
 };
-static opacity_solid opc_solid = opacity_solid();
+static opacity_solid opc_solid;
 
 // LOS bounded by fixed presquared radius.
 struct bounds_radius_sq : bounds_func
@@ -58,7 +66,7 @@ struct bounds_los_radius : bounds_func
 {
     bool operator()(const coord_def& p) const;
 };
-static bounds_los_radius bds_default = bounds_los_radius();
+static bounds_los_radius bds_default;
 
 // Subclasses of this are passed to losight() to modify the
 // LOS calculation. Implementations will have to translate between
-- 
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