Add Perplex noise (Perlin × Simplex multiplied)

- New PerplexNoise generator blends Perlin and Simplex by multiplying outputs
- Registered as PERPLEX in NoiseType enum
- Added PERPLEX and PERPLEX_IRIS styles to NoiseStyle (visible in Noise Explorer)
- Flows into IrisComplex via standard generator registration path

core/src/main/java/com/volmit/iris/engine/object/NoiseStyle.java

@@ -446,6 +446,12 @@ public enum NoiseStyle {
 
     @Desc("Vascular noise gets higher as the position nears a cell border. Cells are distorted using Iris styled wispy noise.")
     VASCULAR_IRIS_HALF(rng -> CNG.signatureHalf(rng, NoiseType.VASCULAR)),
+
+    @Desc("Perplex noise = Perlin x Simplex, multiplied together.")
+    PERPLEX(rng -> new CNG(rng, NoiseType.PERPLEX, 1D, 1)),
+
+    @Desc("Perplex noise with Iris wispy swirls.")
+    PERPLEX_IRIS(rng -> CNG.signature(rng, NoiseType.PERPLEX)),
     ;
 
     private final CNGFactory f;

core/src/main/java/com/volmit/iris/util/noise/NoiseType.java

@@ -28,6 +28,7 @@ public enum NoiseType {
     WHITE_HERMITE((s) -> new InterpolatedNoise(s, WHITE, InterpolationMethod.HERMITE)),
     SIMPLEX(SimplexNoise::new),
     PERLIN(seed -> new PerlinNoise(seed).hermite()),
+    PERPLEX(PerplexNoise::new),
     FRACTAL_BILLOW_SIMPLEX(FractalBillowSimplexNoise::new),
     FRACTAL_BILLOW_PERLIN(FractalBillowPerlinNoise::new),
     FRACTAL_FBM_SIMPLEX(FractalFBMSimplexNoise::new),

core/src/main/java/com/volmit/iris/util/noise/PerplexNoise.java

@@ -0,0 +1,52 @@
+/*
+ * Iris is a World Generator for Minecraft Bukkit Servers
+ * Copyright (c) 2022 Arcane Arts (Volmit Software)
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package com.volmit.iris.util.noise;
+
+import com.volmit.iris.util.math.RNG;
+
+/**
+ * Perplex noise blends Perlin and Simplex noise by multiplying their outputs together.
+ * Both components are normalized to [0,1] so the product stays in [0,1].
+ */
+public class PerplexNoise implements NoiseGenerator {
+    private final NoiseGenerator perlin;
+    private final SimplexNoise simplex;
+
+    public PerplexNoise(long seed) {
+        PerlinNoise p = new PerlinNoise(new RNG(seed).lmax());
+        p.hermite();
+        this.perlin = p;
+        this.simplex = new SimplexNoise(new RNG(seed).lmax());
+    }
+
+    @Override
+    public double noise(double x) {
+        return perlin.noise(x) * simplex.noise(x);
+    }
+
+    @Override
+    public double noise(double x, double z) {
+        return perlin.noise(x, z) * simplex.noise(x, z);
+    }
+
+    @Override
+    public double noise(double x, double y, double z) {
+        return perlin.noise(x, y, z) * simplex.noise(x, y, z);
+    }
+}