lib/noise: fix generation of generated pseudo-random angles

Signed-off-by: Alexis Laferrière <alexis.laf@xymus.net>

diff --git a/lib/noise.nit b/lib/noise.nit
index 3887625..1a0d7ce 100644 (file)
--- a/lib/noise.nit
+++ b/lib/noise.nit
@@ -322,10 +322,20 @@ class InterpolatedNoise
                #
                # These magic prime numbers were determined good enough by
                # non-emperical experimentation. They may need to be changed/improved.
-               var i = 17957*seed + 45127*x + 22613*y
-               var mod = 19031
+               var seed = 817721 + self.seed
+               var i = seed * (x+seed) * 25111217 * (y+seed) * 72233613
+               var mod = 137121
+               var angle = (i.mask.abs%mod).to_f*2.0*pi/mod.to_f
+
+               # Debug code to evaluate the efficiency of the random angle generator
+               # The average of the produced angles should be at pi
+               #
+               #var sum = once new Container[Float](0.0)
+               #var count = once new Container[Float](0.0)
+               #sum.item += angle
+               #count.item += 1.0
+               #if count.item.to_i % 1000 == 0 then print "avg:{sum.item/count.item}/{count.item} i:{i} a:{angle} ({x}, {y}: {seed})"
 
-               var angle = (i%mod).to_f*2.0*pi/mod.to_f
                if w == 0 then return angle.cos
                return angle.sin
        end