Create softening.h

Author: TimGoTheCreator

src/dt/softening.h

@@ -0,0 +1,28 @@
+#pragma once
+#include <cmath>
+
+inline real nextSoftening(real nodeSize,
+                          real nodeMass,
+                          real dist)
+{
+    // Base softening from node size (dominant term)
+    real eps_size = nodeSize * real(0.015);
+
+    // Mass-based softening (heavier nodes get slightly more smoothing)
+    real eps_mass = std::cbrt(nodeMass) * real(0.002);
+
+    // Distance-based tapering:
+    // - strong softening at r → 0
+    // - fades out smoothly as r grows
+    real eps_taper = real(1.0) / (real(1.0) + dist * real(10.0));
+
+    // Combine components
+    real eps = (eps_size + eps_mass) * eps_taper;
+
+    // Minimum floor to avoid zero-softening singularities
+    const real eps_min = real(1e-4);
+    if (eps < eps_min)
+        eps = eps_min;
+
+    return eps;
+}