Rewrite find_ray to use precomputed cellrays.

During precomputation, we store the minimal cellrays by target
and sort them according to niceness.

find_ray now simply picks the first non-blocked ray to a
target, which means looping through the 10 or so minimal
cellrays with that target -- this should be a lot more
efficient. (An extended findray test went from 150s to 40s
(debug) and 40s to 26s (profile)).

The interface to find_ray has changed: cycle_dir=-1,0,1 was
changed to cyle=false/true since we never cycle in the other
direction anyway. find_shortest was removed: all rays to a
target had the same length all along, but now we also return
the straightest one automatically.

The change also eliminates the duplicate corner-cutting code
between ray_def::advance and find_ray as imbalance calculation
now relies on ray_def::advance.

1 files changed, 1 insertions, 1 deletions

diff --git a/crawl-ref/source/beam.cc b/crawl-ref/source/beam.cc
index 50a9a87ff4..fc7c8d2d98 100644
--- a/crawl-ref/source/beam.cc
+++ b/crawl-ref/source/beam.cc
@@ -1592,7 +1592,7 @@ void bolt::choose_ray()
 {
     if (!chose_ray || reflections > 0)
     {
-        if (!find_ray(source, target, ray, 0, true))
+        if (!find_ray(source, target, ray))
             fallback_ray(source, target, ray);
     }
 }