noise: add turbulence (displacement) combiner

Makefile.am

@@ -159,6 +159,8 @@ UTIL_FILES   =			\
     noise/lerp.hpp		\
     noise/lut.cpp		\
     noise/lut.hpp		\
+    noise/turbulence.hpp	\
+    noise/turbulence.ipp	\
     options.cpp			\
     options.hpp			\
     pascal.cpp			\

noise/turbulence.hpp

@@ -0,0 +1,48 @@
+/*
+ * 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 2012-2015 Danny Robson <danny@nerdcruft.net>
+ */
+
+#ifndef __UTIL_NOISE_TURBULENCE_HPP
+#define __UTIL_NOISE_TURBULENCE_HPP
+
+#include "../point.hpp"
+#include "../vector.hpp"
+
+#include <cstdint>
+
+namespace util { namespace noise {
+    /// perturb the evaluation point of a noise function by the results of
+    /// a per-dimension noise function
+    ///
+    /// assumes the pertubation function is roughly symetrical around 0.
+    /// nothing will explode if it isn't, but you'll see strong directional
+    /// artefacts with higher scaling factors.
+    template <typename T, typename D, typename P>
+    struct turbulence {
+        using seed_t = uint64_t;
+        turbulence (seed_t, vector<2,T> scale);
+
+        constexpr T operator() (point<2,T>) const;
+        
+        D data;
+        P perturb[2];
+
+        vector<2,T> scale;
+    };
+} }
+
+#include "turbulence.ipp"
+
+#endif

noise/turbulence.ipp

@@ -0,0 +1,49 @@
+/*
+ * 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 2012-2015 Danny Robson <danny@nerdcruft.net>
+ */
+
+#ifdef __UTIL_NOISE_TURBULENCE_IPP
+#error
+#endif
+#define __UTIL_NOISE_TURBULENCE_IPP
+
+#include "../hash.hpp"
+
+
+namespace util { namespace noise {
+    ///////////////////////////////////////////////////////////////////////////
+    template <typename T, typename D, typename P>
+    turbulence<T,D,P>::turbulence (seed_t _seed,
+                                   vector<2,T> _scale):
+        data (_seed),
+        perturb { wang64 (_seed), wang64 (wang64 (_seed)) },
+        scale (_scale)
+    { ; }
+
+
+    ///////////////////////////////////////////////////////////////////////////
+    template <typename T, typename D, typename P>
+    constexpr T
+    turbulence<T,D,P>::operator() (point<2,T> p) const
+    {
+        vector<2,T> n = {
+            perturb[0] (p),
+            perturb[1] (p)
+        };
+
+        // scale by the data frequency so that we match scale
+        return data (p + n * scale / data.frequency ());
+    }
+} }

tools/noise.cpp

@@ -10,6 +10,7 @@
 #include "noise/basis/value.hpp"
 #include "noise/basis/perlin.hpp"
 #include "noise/basis/worley.hpp"
+#include "noise/turbulence.hpp"
 #include "extent.hpp"
 
 
@@ -28,6 +29,7 @@ main (void)
     uint64_t seed = time (nullptr);
 
     // setup the noise generator
+#if 0
     //util::noise::fractal::fbm<float, util::noise::basis::worley<float>> b (seed);
     //util::noise::fractal::rmf<float, util::noise::basis::worley<float>> b (seed);
     //util::noise::fractal::fbm<float, util::noise::basis::perlin<float,util::lerp::cubic>> b (seed);
@@ -37,9 +39,22 @@ main (void)
 
     b.octaves (8);
     b.frequency (10.f / size.w);
-    //b.lacunarity = 2.f;
-    //b.H = 1.0f;
+    b.lacunarity = 2.f;
+    b.H = 1.0f;
     b.seed (seed);
+#else
+    util::noise::turbulence<
+        float,
+        util::noise::fractal::hetero<float, util::noise::basis::perlin<float,util::lerp::cubic>>,
+        util::noise::fractal::fbm<float, util::noise::basis::perlin<float,util::lerp::quintic>>
+    > b (seed, { 0.13f, 0.13f });
+
+    b.data.frequency (10.f / size.w);
+    b.perturb[0].octaves (4);
+    b.perturb[1].octaves (4);
+    b.perturb[0].frequency (10.f / size.w);
+    b.perturb[1].frequency (10.f / size.w);
+#endif
 
     // generate the values. offset positions slightly to avoid simple axis issues with perlin basis
     {