Merge branch 'dev/fractal-gavoro-pseudoerosion' into ver/6.5.0

common/api/src/main/java/com/dfsek/terra/api/noise/DerivativeNoiseSampler.java

@@ -0,0 +1,41 @@
+package com.dfsek.terra.api.noise;
+
+/**
+ * A NoiseSampler which additionally may provide a 1st directional derivative
+ */
+public interface DerivativeNoiseSampler extends NoiseSampler {
+
+    static boolean isDifferentiable(NoiseSampler sampler) {
+        if (sampler instanceof DerivativeNoiseSampler dSampler) {
+            return dSampler.isDifferentiable();
+        }
+        return false;
+    }
+
+    /**
+     * Samplers may or may not be able to provide a derivative depending on what
+     * inputs they take, this method signals whether this is the case.
+     *
+     * @return If the noise sampler provides a derivative or not
+     */
+    boolean isDifferentiable();
+
+    /**
+     * Derivative return version of standard 2D noise evaluation
+     * @param seed
+     * @param x
+     * @param y
+     * @return 3 element array, in index order: noise value, partial x derivative, partial y derivative
+     */
+    double[] noised(long seed, double x, double y);
+
+    /**
+     * Derivative return version of standard 3D noise evaluation
+     * @param seed
+     * @param x
+     * @param y
+     * @param z
+     * @return 4 element array, in index order: noise value, partial x derivative, partial y derivative, partial z derivative
+     */
+    double[] noised(long seed, double x, double y, double z);
+}