easyRain [HDA]

easyRain is a tool to analyse the rainwater runoff of a [CLOSED GEOMETRY].

By simulating rain particles under gravity and wind, you can obtain rain water trails, which also holds point attributes for velocity and speed.

This tool can also simulate surface tension as rainwater flows around the geometry.

• For current students of mine; Feel free to email/message me and I will provide an HDA for your Houdini Education.

Note: This simulation is an attempt to calculate rainwater runoff. The nature of the tool allows for quick and intuitive uses such as, proof of concepts or early design development.

Inputs

◽ Quality This parameter helps calculate the voxel size for the collision. The voxel size is calculated with a base number and the bounding box size of the input geometry. Custom will overwrite the calculation with the set voxel size written.

◽ Surface Tension **Controls how much the rainwater will attach to the geometry on overhangs, imitating surface tension.

◽ Noise Strength Adds some randomness to the rainwater simulation

◽ Wind Direction Applies some wind to the rainwater simulation

◽ Rain Distribution How to distribute the rain particles from the initiation of the simulation.

• Grid / Density
  • Distribute in a grid of points based on a density parameter
• Scattered / Pt Count
  • Distribute with a set number of scattered points

◽ Colour Velocity Ramp to visualise the velocity

◽ Particles per trail Add rain particles along each rainwater trail

◽ Seed Change the random distribution of the particles

◽ Speed Control the speed at which the particles travel along the trails

Outputs

◽ Attributes: v, speed Point attribute for speed (float) and velocity (vector)

◽ Group: Settling Point group of all points that have settled, to highlight areas that would pool

◽ Out 1: Rain Trails Geometry output of the rainwater trails with the colours of the speed

◽ Out 2: Rain Particles Geometry output of animated particles traveling down the rainwater trails

◽ Out 2: Rain Particles Geometry output of animated particles traveling down the rainwater trails