Whitewater
Spray, foam and bubbles where a liquid crashes and crests: making them, sending each to its own event, and showing them as studios render them.
Big water isn't only its surface: where it crashes into itself or crests fast, it throws off spray, gathers foam on top and churns bubbles inside. VecFlow makes all three from the liquid, as particles of their own.
Start from
A liquid first: the Liquid starter, or your own (see Liquids). Whitewater shows best on big, fast water: a dam break, a wave, a waterfall.
The flow
Add a Whitewater to the liquid's event, and wire each kind you want to an event of its own.
- Spray flies off as its own event says: give it Gravity and a little Drag.
- Foam rides the surface, carried by the liquid.
- Bubbles rise through the liquid at the Whitewater's Bubbles Rise. Turn on Keep Bubbles when objects plunge through the water, so the bubbles on them stay bubbles (see the operator).
- Each turns into another kind as the liquid round it thins or thickens: spray landing becomes foam, foam pushed under becomes bubbles.
- Mist is spray going so fast it breaks into a fine cloud: wire the Mist output to an event of its own. Spray faster than Mist Speed turns to mist at Mist Rate a second; mist drifts with the air (with smoke in the scene, its wind) over Mist Drag seconds, and goes after Mist Life or when it lands in the liquid. Render it small and faint.
- A kind with no wire isn't made at all.
- Give each event a Delete by age Since Birth, or whitewater piles up without end.
How much
- Rate is the most each liquid particle makes a second, where it crashes or crests hardest. Less is a few flecks; more is a white mess.
- Speed is how fast the liquid must go to make any: some from half of it, the most at it. Raise it for big, fast scenes, or a calm surface fizzes; lower it for gentle ones.
How long each lives (its Delete) matters as much: foam that lasts four seconds leaves long trails of lace behind a wave.
How it looks: Whitewater as Foam
Studios render whitewater as many tiny points, not balls, and VecFlow does too. In the Liquid panel, with Whitewater as Foam on (the default):
- each kind has its own Points for each particle, Size (the biggest points' radius; most are smaller) and Spread (how far about its particle they lie). Foam spreads along the water, and only a quarter as much up and down;
- spray is glossy, foam soft and lit through, bubbles faint;
- Fade Out shrinks points over that long before their event's Delete takes them, so none pops out. It reads the Delete's age since birth.
Foam on Water turns the liquid's surface white where foam lies thick on
it, out to Reach from foam's points, so foam reads as patches and lace,
not grains. It needs the surface in the VecFlow Water material, or a
material of yours that reads the surface's foam attribute.
None of this needs a new bake: change it and look.
What goes wrong
- The calm water fizzes. Speed is too low for the scene: raise it.
- Nothing is made. No wire from the kind's output, or the water never goes as fast as half the Speed.
- Whitewater piles up and the bake slows. An event with no Delete.
- Points pop out of sight. Fade Out is shorter than it should be, or the Delete counts Since Entering: Fade Out reads the age since birth.
- Foam looks like grains. Raise Foam on Water and its Reach, and the foam's Points.
Related
Liquid looks
Shaping the liquid's surface for the shot: pushed out or in, cut to the camera, only the main body, values carried onto the mesh, a mesh for each liquid, and wet maps on what it touches.
Smoke
Plumes, wisps, steam and drifting clouds: particles as the source, the gas set in the Smoke and Fire panel, cell size and cost, obstacles, and the volume it renders as.