lib/noise: make compatible with 32 bit archs and a bit more random

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

diff --git a/lib/noise.nit b/lib/noise.nit
index 71dfdfc..3887625 100644 (file)
--- a/lib/noise.nit
+++ b/lib/noise.nit
@@ -66,7 +66,7 @@ abstract class Noise
        # Seed to the random number generator `gradient_vector`
        #
        # By default, `seed` has a random value created with `Int::rand`.
-       var seed: Int = 19559.rand is lazy, writable
+       var seed: Int = 19511359.rand is lazy, writable
 end
 
 # 2D Perlin noise generator using layered `InterpolatedNoise`
@@ -197,7 +197,7 @@ class PerlinNoise
        # Used to get seeds for layers from the previous layers or `seed`.
        protected fun pseudo_random(value: Int): Int
        do
-               return value + 2935391 % 954847
+               return (value * 3537391).mask % 1291377
        end
 end
 
@@ -338,3 +338,14 @@ class InterpolatedNoise
                return dx*gradient_vector(ix, iy, 0) + dy*gradient_vector(ix, iy, 1)
        end
 end
+
+redef universal Int
+       # The value of the least-significant 30 bits of `self`
+       #
+       # This mask is used as compatibility with 32 bits architecture.
+       # The missing 2 bits are used to tag integers by the Nit system.
+       private fun mask: Int
+       do
+               return bin_and(0x3FFF_FFFF)
+       end
+end