VecFlow0.1.0
Effects guides

Snow, rain and confetti

Things that fall through the air: snow drifting in the wind, rain streaking down and splashing, confetti tumbling in many colours.

VecFlow 0.1.0

Snow, rain and confetti fall at the speed the air allows, and the air carries them. Most of the look comes from two settings, Drag and Wind, and the rest from how they're shown.

Start from

  • Snow: flakes drifting down in a breeze.
  • Confetti: paper squares and strips shot up, tumbling down.

Both run on the sidebar's settings, without a flow. Rain needs a flow for its splashes; it's built below.

How they fall

Drag takes a share of the speed each second, against the air, and the air moves with the Wind. A falling thing speeds up until Drag holds it at a top speed: Gravity divided by Drag. So:

DragTop speedFalls like
8about 1.2 m/sSnow (the Snow starter)
1.8about 5.5 m/sConfetti (the Confetti starter)
1about 10 m/sRain
0.15about 65 m/sHardly slowed: stones, sparks (the default)

The more Drag, the faster they're also carried off by the Wind: snowflakes go nearly at the wind's speed, raindrops are only leant over by it. Turbulence adds the gusts and eddies that make each one wander.

Snow

The Snow starter's settings, to change from:

  • Drag 8 and Wind 0.6 m/s along X: a light breeze. Turn it up and lean the emitter into it, so the snow comes from upwind.
  • Strength 1.5 m/s² with Swirl Size 0.6 m: flakes wander. More for a blizzard, with more Wind.
  • Per Frame 120 and Life 6 s, give or take 1: long enough to reach the ground. Raise the rate for heavier snow.
  • Collisions, the Ground's Bounce 0 and Friction 1: flakes land dead instead of skating. The wind still nudges them along the ground a little; for snow that stays put, send landed flakes to an event with a Pin, as the Collide page shows.
  • Scale 0.8, give or take 0.4, and a near-white Fixed colour: a mix of sizes.

For real flakes, point the Display panel's Shapes at a collection of flake models, with Rotation Random and a slow Spin.

Rain

Rain falls fast and splashes where it lands: two stages, so a flow.

A flow of 3 events. Drops: Birth, Position, Speed, Gravity, Drag, Collide, Delete; Collide: ground sends to Splash. Splash: Spawn, Delete; Spawn: 4 each, spread 1.2 m/s, inherit 0 sends to Droplets. Droplets: Scale, Gravity, Collide, Delete.DropsCollide: groundBirth: 1,500 per frame from 1. Make new particles: some every frame, all at once, one on each vertex of an object's mesh (for cloth and ropes: bind them with Bind, Mesh Edges), one on each piece of it (to smash: glue them with Bind, Pieces), or the event's Liquid filling itBirth: 1,500 per frame from 1Position: Cloud, box. Place new particles in an object's box, on its surface or inside it, or along a curve (a tube round it)Position: Cloud, boxSpeed: 8 m/s down. Set the speed of particles entering the event, along a direction (an object's own axes when given), or add it to how they comeSpeed: 8 m/s downGravity: 9.81 m/s². Pull particles down, or any way you point itGravity: 9.81 m/s²Drag: 1, wind 1 m/s. Slow particles to the speed of the air, which moves with the windDrag: 1, wind 1 m/sCollide: ground. Bounce off an object, a collection's objects or the ground, friction slowing their sliding and their spin where they touch. The ones that hit go along the wireCollide: groundDelete: at 3 s. Remove particles at an age (since birth, or since entering this event), or at onceDelete: at 3 sInSplashSpawn: 4 each, spread 1.2 m/s, i…Spawn: 4 each, spread 1.2 m/s, inherit 0. Make new particles from each one, sent along the wire. They start with its looksSpawn: 4 each, spread 1.2 m/s, i…Delete: at once. Remove particles at an age (since birth, or since entering this event), or at onceDelete: at onceInDropletsCollide: groundScale: × 0.4. Set the size of particles entering the eventScale: × 0.4Gravity: 9.81 m/s². Pull particles down, or any way you point itGravity: 9.81 m/s²Collide: ground. Bounce off an object, a collection's objects or the ground, friction slowing their sliding and their spin where they touch. The ones that hit go along the wireCollide: groundDelete: at 0.3 s since entering. Remove particles at an age (since birth, or since entering this event), or at onceDelete: at 0.3 s since enteringIn
Rain: drops fall at their top speed, and each one that hits the ground bursts into four droplets that hop and vanish.BirthForcesPhysicsLooksTests
  • Speed starts them at their top speed, so they don't need a long fall to get there. Set its Direction to (0, 0, -1).
  • Drops read as streaks, not balls: render with motion blur, or show them as Trails one or two frames long. For drops as shapes, a stretched drop with a Rotation Along Motion, Keep Doing It, points down the way it falls.

Confetti

The Confetti starter shows each particle as one of two paper shapes, in many colours:

  • Shapes is the Confetti Shapes collection: a square and a strip. Add your own shapes to it.
  • Rotation Random, Spin 540 °/s, give or take 360: each piece tumbles its own way.
  • Colour Fixed, a grey (0.55, 0.5, 0.5), with Variation 0.5: each of red, green and blue goes up or down by as much as a half, so the grey breaks into every colour. Lower Variation for a party in one colour, around a stronger one.
  • Drag 1.8 and the ground's Friction 0.8: paper flutters down and doesn't slide far.

What goes wrong

  • Snow falls like stones. Drag is too low: at the default 0.15 nothing is slowed much. Snow needs 5 to 10.
  • Flakes stream sideways in a sheet. Too much Wind for the Drag, or no Turbulence to break it up.
  • The ground fills up and the bake slows down. Lifespan off, or too long: each flake stays until its life is over.
  • Confetti shows as balls. No Shapes collection on the Display panel, or it's empty.
  • Drops pass through a roof. Only the Ground is in the starter's Collide: add the roof's object, or put the roofs in a collection and name it in the Collide's Collection.

Sparks, dust and magic

Small, bright particles in streams and bursts: grinder sparks, fireworks, dust in a sunbeam, a trail of magic.

Particles that pile up: sand and grains

Particles that take up room: sand pouring into a heap, gravel, beads, a ball pit. Without a flow, or with Particle Physics in one.

On this page

Start fromHow they fallSnowRainConfettiWhat goes wrongRelated