n/rand: add general keyed random facility

Makefile.am

@@ -172,6 +172,8 @@ UTIL_FILES   =			\
     noise/lut.hpp		\
     noise/midpoint.cpp		\
     noise/midpoint.hpp		\
+    noise/rand.hpp		\
+    noise/rand.ipp		\
     noise/turbulence.hpp	\
     noise/turbulence.ipp	\
     pascal.cpp			\

noise/basis/perlin.hpp

@@ -35,7 +35,6 @@ namespace util { namespace noise { namespace basis {
         seed_t seed (seed_t);
 
     private:
-        vector<2,T> gradient (point<2,intmax_t>) const;
         seed_t m_seed;
     };
 } } }

noise/basis/perlin.ipp

@@ -19,7 +19,7 @@
 #endif
 #define __UTIL_NOISE_BASIS_PERLIN_IPP
 
-#include "../../hash/murmur/murmur2.hpp"
+#include "../rand.hpp"
 
 namespace util { namespace noise { namespace basis {
     ///////////////////////////////////////////////////////////////////////////
@@ -78,10 +78,10 @@ namespace util { namespace noise { namespace basis {
         auto p3 = p_int + util::vector<2,intmax_t> { 1, 1 };
 
         // generate the corner gradients
-        auto g0 = gradient (p0);
+        auto g0 = noise::rand<2,T> (m_seed, p0);
-        auto g1 = gradient (p1);
+        auto g1 = noise::rand<2,T> (m_seed, p1);
-        auto g2 = gradient (p2);
+        auto g2 = noise::rand<2,T> (m_seed, p2);
-        auto g3 = gradient (p3);
+        auto g3 = noise::rand<2,T> (m_seed, p3);
 
         // compute the dot products
         T v0 = dot (g0, p - p0);
@@ -96,25 +96,4 @@ namespace util { namespace noise { namespace basis {
 
         return L_;
     }
-
-    ///////////////////////////////////////////////////////////////////////////
-    template <typename T, lerp_t<T> L>
-    vector<2,T>
-    perlin<T,L>::gradient (point<2,intmax_t> p) const
-    {
-        using util::hash::murmur2::mix;
-
-        auto u = mix (m_seed, mix (uint64_t (p.x), uint64_t (p.y)));
-        auto v = mix (u, m_seed);
-
-        auto r = util::vector<2,T> {
-            (u & 0xffff) / T{0xffff},
-            (v & 0xffff) / T{0xffff}
-        } * 2 - 1;
-
-        CHECK_GE (r, T{-1});
-        CHECK_LE (r, T{ 1});
-
-        return r;
-    }
 } } }

noise/basis/value.hpp

@@ -35,8 +35,6 @@ namespace util { namespace noise { namespace basis {
         seed_t seed (seed_t);
 
     private:
-        T generate (point<2,intmax_t>) const;
-
         seed_t m_seed;
     };
 } } }

noise/basis/value.ipp

@@ -19,7 +19,7 @@
 #endif
 #define __UTIL_NOISE_BASIS_VALIE_IPP
 
-#include "../../hash/murmur/murmur2.hpp"
+#include "../rand.hpp"
 
 namespace util { namespace noise { namespace basis {
     ///////////////////////////////////////////////////////////////////////////
@@ -75,10 +75,10 @@ namespace util { namespace noise { namespace basis {
         auto p3 = p_int + util::vector<2,intmax_t> { 1, 1 };
 
         // Generate the four corner values
-        T g0 = generate (p0);
+        T g0 = noise::rand<float> (m_seed, p0);
-        T g1 = generate (p1);
+        T g1 = noise::rand<float> (m_seed, p1);
-        T g2 = generate (p2);
+        T g2 = noise::rand<float> (m_seed, p2);
-        T g3 = generate (p3);
+        T g3 = noise::rand<float> (m_seed, p3);
 
         // Interpolate on one dimension, then the other.
         auto l0 = L (g0, g1, p_rem.x);
@@ -87,25 +87,4 @@ namespace util { namespace noise { namespace basis {
 
         return l_;
     }
-
-
-    ///////////////////////////////////////////////////////////////////////////
-    // Generate a type from [-UNIT..UNIT]
-    template <typename T, lerp_t<T> L>
-    T
-    value<T,L>::generate (point<2,intmax_t> p) const
-    {
-        using util::hash::murmur2::mix;
-
-        T v = mix (
-            m_seed,
-            mix (
-                uint64_t (p.y),
-                uint64_t (p.x)
-            )
-        ) & 0xffff;
-
-        v = v / T{0xffff} * 2 - 1;
-        return v;
-    }
 } } }

noise/basis/worley.ipp

@@ -21,7 +21,6 @@
 
 
 #include "../../debug.hpp"
-#include "../../hash/murmur/murmur2.hpp"
 
 
 namespace util { namespace noise { namespace basis {

noise/midpoint.cpp

@@ -18,25 +18,7 @@
 
 #include "region.hpp"
 #include "point.hpp"
-#include "hash/murmur/murmur2.hpp"
+#include "rand.hpp"
-
-///////////////////////////////////////////////////////////////////////////////
-template <typename T>
-static T
-gen (uint64_t seed, util::point2u p)
-{
-    using util::hash::murmur2::mix;
-
-    uint64_t v = mix (
-        seed,
-        mix (
-            p.y,
-            p.x
-        )
-    ) & 0xffff;
-
-    return v / T{0xffff} * 2 - 1;
-}
 
 
 ///////////////////////////////////////////////////////////////////////////////
@@ -78,7 +60,7 @@ fill (util::image::buffer<T> &img,
     // do the centre
     {
         const auto avg = (v0 + v1 + v2 + v3) / 4;
-        const auto val = avg + scale * gen<T> (seed, target.centre ());
+        const auto val = avg + scale * util::noise::rand<T> (seed, target.centre ());
         const auto pos = target.p + target.e / 2;
 
         img[pos] = val;
@@ -91,10 +73,10 @@ fill (util::image::buffer<T> &img,
         const auto p32 = target.p + util::vector2u{w/2,   h-1};
         const auto p20 = target.p + util::vector2u{0,     h/2};
 
-        const auto v01 = (v0 + v1) / 2 + sides * scale * gen<T> (seed, p01);
+        const auto v01 = (v0 + v1) / 2 + sides * scale * util::noise::rand<T> (seed, p01);
-        const auto v13 = (v1 + v3) / 2 + sides * scale * gen<T> (seed, p13);
+        const auto v13 = (v1 + v3) / 2 + sides * scale * util::noise::rand<T> (seed, p13);
-        const auto v32 = (v3 + v2) / 2 + sides * scale * gen<T> (seed, p32);
+        const auto v32 = (v3 + v2) / 2 + sides * scale * util::noise::rand<T> (seed, p32);
-        const auto v20 = (v2 + v0) / 2 + sides * scale * gen<T> (seed, p20);
+        const auto v20 = (v2 + v0) / 2 + sides * scale * util::noise::rand<T> (seed, p20);
 
         img[p01] = v01;
         img[p13] = v13;
@@ -119,10 +101,15 @@ template <typename T>
 void
 util::noise::midpoint (image::buffer<T> &img, uint64_t seed, float persistence, float sides)
 {
-    img[{0,             0}] = gen<T> (seed, { 0,       0 });
+    static const util::point2u CORNERS[] = {
-    img[{0,       img.w-1}] = gen<T> (seed, { 0,       img.w-1 });
+        { 0,         0 },
-    img[{img.h-1,       0}] = gen<T> (seed, { img.h-1, 0 });
+        { 0,         img.w - 1 },
-    img[{img.h-1, img.w-1}] = gen<T> (seed, { img.h-1, img.w-1 });
+        { img.h - 1, 0 },
+        { img.h - 1, img.w - 1 }
+    };
+
+    for (auto i: CORNERS)
+        img[i] = util::noise::rand<T> (seed, i);
 
     fill (img, seed, { { 0, 0 }, img.extent () }, 1.f, persistence, sides);
 }

noise/rand.hpp

@@ -0,0 +1,33 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * Copyright 2015 Danny Robson <danny@nerdcruft.net>
+ */
+
+#ifndef __UTIL_NOISE_RAND_HPP
+#define __UTIL_NOISE_RAND_HPP
+
+namespace util { namespace noise {
+    /// generate a uniform random floating point in the range [-1, 1] from a seed and vector
+    template <typename T, typename V>
+    T
+    rand (uint64_t seed, V value);
+
+    template <size_t N, typename T, typename V>
+    vector<N,T>
+    rand (uint64_t seed, V value);
+} }
+
+#include "rand.ipp"
+
+#endif

noise/rand.ipp

@@ -0,0 +1,60 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * Copyright 2015 Danny Robson <danny@nerdcruft.net>
+ */
+
+
+#ifdef __UTIL_NOISE_RAND_IPP
+#error
+#endif
+#define __UTIL_NOISE_RAND_IPP
+
+#include "../hash/murmur/murmur2.hpp"
+
+
+namespace util { namespace noise {
+    template <typename T, typename V>
+    T
+    rand (uint64_t seed, V value)
+    {
+        uint64_t accum = seed;
+        for (auto i: value)
+            accum = hash::murmur2::mix (accum, i);
+
+        T out = (accum & 0xFFFF) / T{0xFFFF};
+
+        out *= 2;
+        out -= 1;
+
+        return out;
+    }
+
+
+    template <size_t N, typename T, typename V>
+    vector<N,T>
+    rand (uint64_t seed, V value)
+    {
+        uint64_t accum = seed;
+        for (auto i: value)
+            accum = hash::murmur2::mix (accum, i);
+
+        vector<N,T> out;
+        for (auto &i: out) {
+            i = (accum & 0xFFFF) / T{0xFFFF};
+            accum = hash::murmur2::mix (accum, seed);
+        }
+
+        return out * 2 - 1;
+    }
+} }