Installing Rain Paint

Rain Paint can be installed just like any other addon! Under Edit > Preferences > Addons > Install select the downloaded .zip file, enabled Rain Paint and you should be ready to start simulating!

Getting started

Now you've installed Rain Paint you should be able to see the 'Rain Paint' tab in the 3D views right-hand toolbar. Let's take a closer look at the user parameters.

Target object: the mesh the simulation will run on.

Rain density: controls how many raindrops will be spawned per simulation. This number is relative to the number of vertices in your target model. A model with 10 vertices and a Rain density of 1 will randomly spawn 10 raindrops. A Rain density of 2 will randomly spawn 20 drops. *Be careful with high detailed models as a high rain density can cause Blender to become unstable.

Droplet lifetime: the maximum number of steps that a raindrop will live for before despawning. More detailed terrain may require a higher droplet lifetime to ensure the droplets live long enough to reach their local minimum values.

Ground brittleness: determines how quickly the ground will erode. Higher values (between 0.5 - 0.8) will simulate materials like snow or sand, whereas lower values (0.001- 0.2) will simulate materials rock and solid dirt.

Drop volume: this can be thought of as the 'size' of each raindrop. A larger drop is going to have a bigger impact on the surface over a small droplet.

Use vertex group?: toggle between simulating on the entire model or a specific area. If checked, the list of vertex groups for the target model will appear to be chosen from.

Getting the most out of Rain Paint

If you're expecting slow simulation times or undesired effects try:

• Lowing your model resolution and using a subdivide-surface modifier. Simulation times are directly tied to the number of vertices in a model. Allowing the subdivide-surface modifier to handle the smoothing out of terrain can drastically speed up simulation times.
• Use smaller increments. Try changing the values by 0.1, or 0.01. It can be easy to scale the simulation up to overdramatic results.
• Balance 'Rain density', 'Ground brittleness', and 'Drop volume'. Slightly lowering 'Rain density' and increasing 'Drop volume' will spawn fewer raindrops but make the ones that are spawned a little more aggressive, helping with simulation times. Similarly, if you want to run one 'harsh' simulation instead of multiple 'soft' simulations, increase the 'Ground brittleness'.