[orx-math] Add RBF interpolation utilities with 2D interpolator, demos, and shader phrases

orx-shader-phrases/src/commonMain/kotlin/rbf/RbfPhrases.kt

@@ -0,0 +1,51 @@
+package org.openrndr.extra.shaderphrases.rbf
+
+/**
+ * A constant string defining a C-style preprocessor directive and implementation for the
+ * Radial Basis Function (RBF) Gaussian formula in a shader or computational context.
+ *
+ * The definition includes a function `rbfGaussian` that computes the Gaussian value
+ * based on the squared distance and scale factor. It utilizes the exponential function
+ * for the calculation.
+ */
+const val rbfGaussianPhrase = """#ifndef SP_RBF_GAUSSIAN
+#define SP_RBF_GAUSSIAN
+float rbfGaussian(float sqrDistance, float scale) {
+    return exp(-sqrDistance * scale * scale);
+}
+#endif
+"""
+
+/**
+ * A constant string representing a shader function definition for the
+ * Radial Basis Function (RBF) using the inverse quadratic formula.
+ *
+ * The function `rbfInverseQuadratic` calculates the RBF value based on
+ * squared distance and a scale factor.
+ *
+ * The formula for the RBF is:
+ *  1.0 / (1.0 + sqrDistance * scale^2)
+ */
+const val rbfInverseQuadraticPhrase = """#ifndef SP_RBF_INVERSE_QUADRATIC
+#define SP_RBF_INVERSE_QUADRATIC
+float rbfInverseQuadratic(float sqrDistance, float scale) {
+    return 1.0 / (1.0 + sqrDistance * scale * scale);
+}
+#endif
+"""
+
+/**
+ * Represents the implementation of the inverse multiquadratic radial basis function (RBF)
+ * in shader language. This constant holds the shader source code for calculating
+ * the inverse multiquadratic RBF given a squared distance and a scale factor.
+ *
+ * The function defined within this shader code computes the RBF as:
+ * 1.0 / sqrt(1.0 + sqrDistance * scale * scale)
+ */
+const val rbfInverseMultiQuadraticPhrase = """#ifndef SP_RBF_INVERSE_MULTIQUADRATIC
+#define SP_RBF_INVERSE_MULTIQUADRATIC
+float rbfInverseMultiQuadratic(float sqrDistance, float scale) {
+    return 1.0 / sqrt(1.0 + sqrDistance * scale * scale);
+}
+#endif
+"""