Falling raindrops create ripple rings on puddles, dynamic clouds drift overhead and an optional rainbow appears. Four weather modes: light rain, storm, drizzle and sunny rain.
Particle system for raindrops with gravity. Ripple rings expand on impact using wave interference. Cloud layer uses Perlin noise for natural movement.
Switch between four weather modes. Watch ripple patterns form on puddle surfaces. The rainbow appears when sun angle and rain coexist.
Real raindrops are not teardrop-shaped — small ones are spherical, and large ones (>2mm) become flattened hamburger-buns due to air resistance. Very large drops break apart.
This simulation models falling rain as a particle system: each raindrop is an independent particle that accelerates under gravity and is pushed sideways by an adjustable wind vector. When a drop reaches the wet ground it is removed and spawns an expanding ripple ring plus a short-lived spray of splash particles, while drifting cloud puffs and an optional half-circle rainbow complete the scene. Four weather presets — light rain, storm, drizzle and sunny rain — change drop count, wind, cloud darkness and sky colour.
Real rainfall is governed by fluid dynamics and aerodynamics: a falling drop reaches a terminal velocity (about 9 m/s for a typical 2 mm drop) where air drag balances gravity, and surface tension keeps small drops nearly spherical rather than tear-shaped. The ripples mimic circular surface waves, and the rainbow reproduces the 42° refraction-and-reflection angle that splits sunlight into colours. The same particle-and-collision techniques are used for weather effects in games, film visual effects and scientific visualisations of precipitation.
What does the Rain & Puddles simulation show?
It shows raindrops falling under gravity and wind, splashing into puddles to create expanding ripple rings, with drifting clouds and an optional rainbow. You can switch between rain, storm, drizzle and sunny-rain weather modes.
Are raindrops really teardrop-shaped?
No. Small raindrops are nearly perfect spheres held together by surface tension. Larger drops (above about 2 mm) flatten into a hamburger-bun shape from air resistance, and very large drops break apart — none look like the classic pointed teardrop.
How fast does rain actually fall?
A drop accelerates until air drag balances gravity, reaching terminal velocity. A typical 2 mm raindrop falls at roughly 9 metres per second, while tiny drizzle droplets fall much more slowly, around 1-2 m/s.
Each drop is a particle with a position and velocity. Gravity is added to its vertical speed every frame, wind is added to its horizontal speed, and when it crosses the ground line it is deleted and replaced by a ripple plus splash particles.
When a drop hits a water surface it disturbs it at a single point, and that disturbance spreads outward equally in all directions as a circular surface wave — so the visible ring expands while fading, just like real ripples on a puddle.
The rainbow fades in only in the "sunny rain" mode, mimicking how a rainbow needs both sunlight and falling rain. Real rainbows form when light refracts entering a drop, reflects inside, and refracts again leaving, separating colours at about a 42° angle.
Rain is a steady moderate shower, storm has dense fast drops with strong wind and dark clouds, drizzle has sparse slow droplets, and sunny rain combines light rain with bright skies and a rainbow. Each preset adjusts drop count, wind and colours.
Yes. Clicking the sky triggers an extra burst of drops, and clicking the ground creates an instant ripple and splash. You can also drag the intensity and wind sliders to fine-tune the storm.
No — Earth recycles the same water continuously through the water cycle. Rain evaporates, condenses into clouds and falls again, so the water in a raindrop may be millions of years old and has fallen countless times before.
It illustrates terminal velocity, gravity and drag, surface waves, the water cycle and the optics of rainbows, all through a real-time particle system of the kind used for weather effects in games and films.