n/basis: add patch basis function

Makefile.am

@@ -149,6 +149,8 @@ UTIL_FILES   =			\
     noise/basis/constant.cpp	\
     noise/basis/constant.hpp	\
     noise/basis/constant.ipp	\
+    noise/basis/patch.hpp	\
+    noise/basis/patch.ipp	\
     noise/basis/perlin.hpp	\
     noise/basis/perlin.ipp	\
     noise/basis/runtime.cpp	\

noise/basis/patch.hpp

@@ -0,0 +1,43 @@
+/*
+ * 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_BASIS_PATCH_HPP
+#define __UTIL_NOISE_BASIS_PATCH_HPP
+
+#include "point.hpp"
+
+namespace util { namespace noise { namespace basis {
+    template <typename T>
+    struct patch {
+        patch (seed_t);
+        
+        range<T> bounds (void) const;
+        T operator() (point2<T>) const;
+        
+        seed_t seed (void) const;
+        seed_t seed (seed_t);
+
+    private:
+        point2<T> centroid (util::point2i) const;
+        T generate (util::point2i) const;
+
+        seed_t m_seed;        
+    };
+} } }
+
+#include "patch.ipp"
+
+#endif

noise/basis/patch.ipp

@@ -0,0 +1,117 @@
+/*
+ * 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>
+ */
+
+#if defined(__UTIL_NOISE_BASIS_PATCH_IPP)
+#error
+#endif
+#define __UTIL_NOISE_BASIS_PATCH_IPP
+
+
+///////////////////////////////////////////////////////////////////////////////
+template <typename T>
+util::noise::basis::patch<T>::patch (seed_t _seed):
+    m_seed (_seed)
+{ ; }
+
+
+///////////////////////////////////////////////////////////////////////////////
+template <typename T>
+util::range<T>
+util::noise::basis::patch<T>::bounds (void) const
+{
+    return { T{0}, T{1} };
+}
+
+
+///////////////////////////////////////////////////////////////////////////////
+template <typename T>
+T
+util::noise::basis::patch<T>::operator () (point2<T> p) const
+{
+    // extract integer and fractional parts. be careful to always round down
+    // (particularly with negatives) and avoid rounding errors.
+    auto p_int = p.template cast<intmax_t> ();
+    if (p.x < 0) p_int.x -= 1;
+    if (p.y < 0) p_int.y -= 1;
+    auto p_rem = (p - p_int).template as<point> ();
+
+    T closest = std::numeric_limits<T>::infinity ();
+    T value;
+
+    for (signed y = -1; y <= 1; ++y)
+        for (signed x = -1; x <= 1; ++x) {
+            util::vector2i offset {x, y};
+            auto c = centroid (p_int + offset);
+            auto d = util::distance (p_rem, c + offset);
+
+            if (d < closest) {
+                closest = d;
+                value = generate (p_int + offset);
+            }
+        }
+
+    return value;
+}
+
+
+///////////////////////////////////////////////////////////////////////////////
+template <typename T>
+util::noise::seed_t
+util::noise::basis::patch<T>::seed (void) const
+{
+    return m_seed;
+}
+
+
+//-----------------------------------------------------------------------------
+template <typename T>
+util::noise::seed_t
+util::noise::basis::patch<T>::seed (util::noise::seed_t _seed)
+{
+    return m_seed = _seed;
+}
+
+
+///////////////////////////////////////////////////////////////////////////////
+template <typename T>
+util::point2<T>
+util::noise::basis::patch<T>::centroid (util::point2i 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::point<2,T> {
+        (u & 0xffff) / T{0xffff},
+        (v & 0xffff) / T{0xffff}
+    };
+
+    CHECK_LIMIT (r, T{0}, T{1});
+    return r;
+}
+
+
+//-----------------------------------------------------------------------------
+template <typename T>
+T
+util::noise::basis::patch<T>::generate (util::point2i p) const
+{
+    using util::hash::murmur2::mix;
+
+    auto u = mix (m_seed, mix (uint64_t (p.x), uint64_t (p.y)));
+    return (u & 0xffff) / T{0xffff};
+}

tools/noise.cpp

@@ -9,6 +9,7 @@
 #include "noise/lerp.hpp"
 #include "noise/basis/constant.hpp"
 #include "noise/basis/value.hpp"
+#include "noise/basis/patch.hpp"
 #include "noise/basis/perlin.hpp"
 #include "noise/basis/worley.hpp"
 #include "noise/turbulence.hpp"
@@ -34,7 +35,8 @@ template struct util::noise::fractal::hetero<float, util::noise::basis::worley<f
 enum basis_t {
     VALUE,
     PERLIN,
-    WORLEY
+    WORLEY,
+    PATCH
 };
 
 
@@ -67,6 +69,7 @@ operator>> (std::istream &is, basis_t &b)
     b = name == "value"     ? VALUE  :
         name == "perlin"    ? PERLIN :
         name == "worley"    ? WORLEY :
+        name == "patch"     ? PATCH  :
         (is.setstate (std::istream::failbit), b);
 
     return is;
@@ -78,9 +81,10 @@ std::ostream&
 operator<< (std::ostream &os, basis_t b)
 {
     switch (b) {
-        case VALUE: os << "value"; return os;
+        case VALUE:     os << "value";  return os;
-        case PERLIN: os << "perlin"; return os;
+        case PERLIN:    os << "perlin"; return os;
-        case WORLEY: os << "worley"; return os;
+        case WORLEY:    os << "worley"; return os;
+        case PATCH:     os << "patch";  return os;
 
         default:
             unreachable ();
@@ -288,6 +292,11 @@ main (int argc, char **argv)
             break;
         }
 
+        case PATCH: {
+            b.reset<util::noise::basis::patch<float>> (seed);
+            break;
+        }
+
         default:
             unreachable ();
     }