🌊 Pure Rain Smooth – Rain Filter Implementation

Abstract

Pure Rain Smooth is a stochastic mesh-smoothing add-on for Blender. It applies noise droplets always pushing inward—never zero, never outward—exactly as prescribed by the Rain Filter Curvature-conditioned magnitude and anti phase direction yield an emergent "low-pass"-like effect without explicit convolutions.

💧 Introduction

The Rain Filter proposes a smoothing approach in which random noise acts as an emergent filter. Unlike deterministic methods—e.g., classical Laplacian—this model drops stochastic perturbations onto the mesh and applies them in anti phase with the vertex normal. The final result is global smoothing, yet the magic lies in the intermediate steps and their controlled randomness. 🪄

📖Core Doctrine

• Antiphase push: Displacement direction is always inverse to the phase (in meshes it's assumed as a unipolar signal).
• Droplets never zero: Every selected vertex has a non-zero chance (density) each sub-pass; magnitude random(0,1) ensures some push.
• Curvature-weighted magnitude: logCoeff = log(1+steepness·κ)/log(1+steepness) (κ ≥ 0). Peaks ≈ 1, planes ≈ ½, valleys > 0.
• No deterministic kernels: Smoothing emerges from repeated noise impacts—no Laplacian matrix, no explicit diffusion.

➕ Optional Features

• Tangential Passes: Hits along two orthogonal directions for isotropic feel.
• Interleaved Tangents: Shuffle order Normal → T1 → T2 within each iteration (acts like a "detangler").
• Burst Rain Mode: Timer-driven loop; click Play for continuous drizzle, Pause to stop.

🌧️ Algorithm

• Local relief: κ=max((v−centroid)⋅n,0)
• Log gain: logCoeff=log(1+steepness⋅κ)/log(1+steepness)
• Drop magnitude: ∣Δ∣=intensity⋅rand(0,1)⋅logCoeff
• Direction: −n or tangents (optional).
• Clamp: ∣Δ∣≤maxDisp
• Iterate: Fixed Iterations per click, or endless timer in Burst mode.

📊 Parameters

Here's a breakdown of the controls you'll find for Pure Rain Smooth:

• Intensity: 0 – 5 (Core) – This is your global strength multiplier.
• Density: 0 – 1 (Core) – The probability each vertex gets hit per sub-pass.
• Iterations: 1 – 500 (Core) – How many times the effect is applied (this is hidden in Burst mode).
• Steepness: 0.1 – 10 (Core) – Controls how much curvature influences the effect. 0.1 is more linear, 10 is very logarithmic.
• Max Disp: 0.001 – 1 BU (Core) – A safety clamp per droplet to prevent extreme deformations.
• Tangent Rain: bool (Extra) – Enable this to add two orthogonal passes for a more uniform feel.
• Interleaved Tangents: bool (Extra) – Cycles through Normal → T1 → T2 every loop for a smoother blend.
• Interval (s): 0.01 – 5 (Extra) – Sets the timer period when using Burst mode for continuous application.

🛁 Usage

1. In Edit Mode, select the vertices you want to tame.
2. Set sliders (Intensity, Density, etc.).
3. Choose your mode:
   • One-shot: Press Rain.
   • Continuous: Open Burst Rain Mode, set Interval, press Play (stop with Pause).
4. Optionally enable Tangential Passes or Interleaved for a rounder wash.

🗺️ Roadmap

• Vertex and Weight-map modulation (paint where it rains harder).

🎣 Credits

• Concept & Algorithm Design — David Rodriguez
• The Sea, which was my inspiration and reference.

📜 License

Pure Rain Smooth is free software, licensed under the GNU GPL v3.

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Happy blending!