# util Small shared helpers for the other juiceKit modules. Vectors as `{x,y,z}` maps (`vec` accepts arrays, maps and vectors), quaternions as `{x,y,z,w}` maps (`q` accepts arrays too), a seeded `rng`, `clamp` and `lerp`, and target resolution: `entityOf`, `positionOf`, `localAvatar`, `cameraEntity` and `cameraPos`. Also `rgba` for UI colours and `isPlaying`.

# JuiceShakeApply Attached to the scene camera by `juiceKit.shake`; you never add it yourself. It runs late (execution order 10000), after every camera controller, and adds the current shake offset to the camera's pose, remembering exactly what it added.

# JuiceShakeRestore Attached to the scene camera with JuiceShakeApply. It runs early (execution order -99), before the camera controllers, and removes the offset JuiceShakeApply added the frame before, so controllers always see the clean pose and the camera never drifts.

# juiceKit **One call makes hits, explosions, pickups and level-ups feel great: `Juice.play("explosionLarge", someEntity)` shakes the camera, flashes the screen, freezes the action for a beat, squashes the target and plays an effect at the spot, all together and correctly for every player.** Version **1.2.2** (`Juice.VERSION`). The version, this README and `package.yaml` move together. ## First example 1. Install juiceKit into your world. 2. Create a component named `juiceDemo` (a `juiceDemo.component` folder with this `init.luau`). 3. Add `juiceDemo` to any entity in your scene, press Play and press **E** (Interact). Each press plays the next of the three effects. ```lua local Juice = require("juiceKit.juice") declare {} public = { inputMap = Field.assetRef("inputMap", "@builtin::inputMaps.default", NoSync, "The controls the Interact press comes from."), } local controls = nil local presses = 0 function start() controls = public.inputMap:activate("juiceDemo") controls.interact:onPressed(function() presses += 1 local here = public.entity if presses % 3 == 1 then -- an explosion at this entity: everyone sees it, and each player -- feels the shake as strongly as their distance to it warrants Juice.play("explosionLarge", here) elseif presses % 3 == 2 then -- a coin pickup at a point in the world Juice.play("coinPickup", { 4, 1, 2 }) else -- the local player got hurt by an attacker standing at this entity: -- red vignette, a short freeze, a kick away from it (only this player) Juice.play("hurt", nil, { from = here }) end end) end function onDestroy() if controls then public.inputMap:deactivate(controls) end end ``` Nothing else is needed. Only the player who pressed E calls `play`, so the default routing is right: the explosion and the coin reach every player, and the hurt stays with this one. Requiring `juiceKit.juice` starts listening for other peers' effects, and the first shake attaches the shake components to the camera on screen. To make sure a peer whose own scripts never call `play` still receives world effects, put the **JuiceNet** component on any scene entity. Its `look` field also sets the starting look. ## Swapping things Everything goes through the same call, so a different preset, look or strength is a one-word change: ```lua Juice.play("hitLight", enemy) -- -> "hitHeavy", "hitCritical" Juice.play("vfxFire", pos, { look = "pixel" }) -- one effect in another look Juice.setLook("realistic") -- every effect from now on Juice.play("shakeExplosion", pos, { intensity = 0.5 }) -- half strength, this call only ``` ## Presets (51) Kinds: `combo`, `shake`, `hitstop`, `flash`, `squash` and `vfx`. Strengths: `light`, `medium` and `heavy`. Scope is `player` (it happens only for the player it is about) or `world` (every peer sees it). `hurt`, `heal`, `death`, `levelUp` and `landingHard` also carry `personal = "player"`: their screen parts play only for a player who is the target, never for whoever called `play`. See the multiplayer rules below. | name | kind | strength | scope | pieces | what it is | |---|---|---|---|---|---| | `coinPickup` | combo | light | world | squash + vfx | A coin sparkle and pulse. | | `death` | combo | heavy | world | shake + hitstop + flash + squash + vfx | A death: crushed flat, smoke, a slow-motion freeze, and a dark fade for the player who died. | | `explosionLarge` | combo | heavy | world | shake + hitstop + flash + squash + vfx | A big blast: fireball, debris, a dust ring, a flash and a shake everyone feels by distance. | | `explosionSmall` | combo | medium | world | shake + squash + vfx | A small blast: fireball, smoke and a distance-scaled shake. | | `heal` | combo | light | world | flash + squash + vfx | Healing: rising green motes and a soft green pulse for the healed player. | | `hitCritical` | combo | heavy | world | shake + hitstop + flash + squash + vfx | A critical: a long freeze into slow motion, a hot flash, a kick away from the attacker and zap sparks. | | `hitHeavy` | combo | medium | world | shake + hitstop + flash + squash + vfx | A heavy hit: bigger sparks, a freeze, a strong shake and a flash. | | `hitLight` | combo | light | world | shake + hitstop + squash + vfx | A light hit: sparks, a tiny freeze, a small shake and a wobble. | | `hurt` | combo | medium | player | shake + hitstop + flash | Taking damage: a red vignette, a kick away from the attacker and a tiny freeze. | | `landingHard` | combo | medium | world | shake + squash + vfx | A hard landing: a dust ring, a landing squash and a short heavy shake. | | `levelUp` | combo | heavy | world | shake + flash + squash + vfx | Level up: a golden column, a ring, confetti, a golden glow and a stretch. | | `spawn` | combo | light | world | squash + vfx | Something appears: a pop-in with a magic burst. | | `shakeEarthquake` | shake | heavy | world | shake | A rolling earthquake that swells, peaks and fades over four seconds for everyone nearby. | | `shakeExplosion` | shake | heavy | world | shake | A blast shake that every player feels, weaker the farther they are from it. | | `shakeHeavy` | shake | heavy | player | shake | A strong jolt for big hits and slams. | | `shakeKick` | shake | medium | player | shake | A directional kick that pushes the view away from where the hit came from (pass `from` or `direction`). | | `shakeLight` | shake | light | player | shake | A quick, small jitter for light hits and footfalls. | | `shakeRecoil` | shake | light | player | shake | A weapon recoil: the view snaps back and up, then settles. | | `shakeRumble` | shake | medium | player | shake | A long, low rumble for engines, collapsing rock or a boss approaching. | | `hitstopCritical` | hitstop | heavy | player | hitstop | A 180 ms freeze that eases out through slow motion, for critical hits and finishers. | | `hitstopHeavy` | hitstop | medium | player | hitstop | A 120 ms freeze for heavy blows. | | `hitstopLight` | hitstop | light | player | hitstop | A 50 ms freeze that lands a light hit. | | `hitstopSlowmo` | hitstop | medium | player | hitstop | Half a second of 25% slow motion with no freeze, for near misses and dramatic moments. | | `flashBlackout` | flash | heavy | player | flash | A fade to black and back, for death, respawn or a scene cut. | | `flashCritical` | flash | heavy | player | flash | A blinding white-orange burst with hot edges. | | `flashDamage` | flash | medium | player | flash | A red vignette that closes in from the screen edges when you take damage. | | `flashExplosion` | flash | medium | world | flash | A bright blast flash every player near the explosion sees. | | `flashFreeze` | flash | light | player | flash | An icy blue vignette for frozen, chilled or shielded. | | `flashHeal` | flash | light | player | flash | A soft green pulse from the edges. | | `flashHit` | flash | light | player | flash | A sharp white flash across the screen. | | `flashLevelUp` | flash | medium | player | flash | A warm golden glow that blooms and fades. | | `flashPoison` | flash | light | player | flash | A sickly purple-green vignette for poison and curses. | | `flatten` | squash | heavy | world | squash | Crushed flat, held, then springs back up, for deaths and stomps. | | `jellyWobble` | squash | light | world | squash | A jelly wobble when something is hit. | | `popIn` | squash | medium | world | squash | Grows from nothing with an overshoot, for spawns and pickups appearing. | | `pulse` | squash | light | world | squash | A quick uniform bump for collect, select or a heartbeat. | | `punch` | squash | heavy | world | squash | A hard punch inward that rings out, for heavy impacts. | | `squashLand` | squash | medium | world | squash | Flattens on landing and springs back. | | `stretchJump` | squash | medium | world | squash | Stretches tall on take-off and settles. | | `vfxCoin` | vfx | light | world | vfx | A coin sparkle. | | `vfxConfetti` | vfx | medium | world | vfx | A confetti burst. | | `vfxDust` | vfx | light | world | vfx | A dust puff. | | `vfxExplosionLarge` | vfx | heavy | world | vfx | A large explosion: fireball, debris and a smoke ring. | | `vfxExplosionSmall` | vfx | medium | world | vfx | A small explosion. | | `vfxFire` | vfx | medium | world | vfx | A burst of fire. | | `vfxHeal` | vfx | medium | world | vfx | Rising healing motes. | | `vfxLevelUp` | vfx | medium | world | vfx | A level-up column and ring. | | `vfxMagic` | vfx | medium | world | vfx | A magic burst. | | `vfxSmoke` | vfx | medium | world | vfx | A smoke cloud. | | `vfxSparks` | vfx | light | world | vfx | Impact sparks. | | `vfxZap` | vfx | medium | world | vfx | An electric zap. | Every `vfx` preset and every combo's effect is drawn in the current look: **cartoon** (solid toon shapes, the default), **realistic** (soft additive glow, smoke and dark debris), **pixel** (chunky cubes snapped to a grid) or **scifi** (cyan and magenta energy). Effect kinds: `sparks`, `dust`, `explosionSmall`, `explosionLarge`, `magic`, `heal`, `levelUp`, `coin`, `smoke`, `fire`, `zap` and `confetti`. ## Interface (`require("juiceKit.juice")`) ### Playing `Juice.play(name, target?, opts?) -> result` plays a preset. It raises on an unknown preset, look or target, and otherwise returns a table saying what ran on this peer: `{ shake = strength, hitstop = true, flash = alpha, squash = true, vfx = particleCount, sent = true, id = playId }`. Every play gets an `id`, even one that intensity 0 turned into nothing, so the result can always be handed to `Juice.stop`. - `target`: an entity, an entity id, an entity name, a position (`{x,y,z}`, `{x=,y=,z=}` or a vector), or nil for the local player. - `opts`: | option | meaning | |---|---| | `intensity` | Multiplier for this call (multiplied by the global intensity). | | `look` | Draws this call's effect in a look other than the current one. | | `from` | The attacker: an entity or a position. Kicks push away from it, and when the target is a thing (not a player) and `from` is another player's avatar, the personal parts land on that attacking player's screen. | | `direction` | World direction the hit travels, used instead of `from`. | | `scale` | Effect size multiplier. | | `axis` | Squash axis: `"y"` (default), `"x"` or `"z"`. | | `scope` | `"auto"` (default): world parts go to every peer, personal parts to the one player they belong to. `"local"`: play here only what belongs on this peer and send nothing, for code that already runs on every peer. `"world"`: also send a player preset's world parts to every peer. | | `seed` | Seed for a repeatable effect. | `Juice.stop(what) -> boolean` stops one play early and leaves everything else running. `what` is the table `play` returned, its `id`, or a preset name; a name stops every play of that preset on this peer, its own and ones received from other peers. ```lua local charge = Juice.play("shakeRumble") -- the charge was cancelled: Juice.stop(charge) ``` - The shake comes off the camera with no drift; other shakes keep going. - The hitstop lets go: normal speed comes back at once unless another hitstop still holds. - The flash disappears, the squash lands on the exact base scale, and the effect's particles and light vanish. - Stopping a play this peer sent to others stops it on their screens too. - It returns false for a play that has already finished or was stopped, and for nil. An unknown preset name raises. `Juice.isPlaying(what) -> boolean` says whether any part of a play (same `what` as `stop`) is still running here. `Juice.stopAll()` stops every shake, hitstop, flash, squash and effect at once, puts squashed things back at their exact base scale, and releases the time scale. It acts on this peer only and forgets every play id. ### Finding presets - `Juice.list(filter?) -> rows` returns every preset as `{ name, kind, strength, scope, personal, looks, pieces, effects, tags, custom, description }`, sorted by kind and then name. - A **kind name** string (`"shake"`, `"combo"`, …) keeps that kind. - Any other string matches a tag or a name (`"heavy"`, `"world"`, `"explosion"`, `"custom"`). - A table `{ kind?, strength?, scope?, look?, piece?, tag?, custom? }` requires all of its fields. - `Juice.names(filter?) -> { string }` returns the same rows as `list`, names only. - `Juice.get(name) -> row?` returns one row plus `spec`, the resolved pieces. Both are copies: changing them never changes the preset. - `Juice.has(name) -> boolean` says whether a preset by that name exists. - Constants: `Juice.KINDS`, `Juice.STRENGTHS`, `Juice.SCOPES` and `Juice.PIECES`. ### Making your own `Juice.define(name, spec) -> row` adds a preset, or replaces one you defined earlier. Each piece in `spec` is either the name of an existing preset of that kind or a table of its own: ```lua Juice.define("bossSlam", { shake = "shakeEarthquake", hitstop = "hitstopHeavy", flash = "flashExplosion", squash = "punch", vfx = { kind = "explosionLarge", scale = 1.6 }, strength = "heavy", scope = "world", tags = { "boss" }, description = "The boss hits the floor.", }) Juice.play("bossSlam", boss) ``` Besides the pieces, `spec` takes `kind`, `strength`, `scope` (`"player"` or `"world"`, worked out from the pieces when left out), `personal` (`"target"`, the default, or `"player"` for moments that only make sense for a player; see the multiplayer rules), `tags` and `description`. Your presets can be built on each other (`Juice.define("bossSlamBig", { shake = "bossSlam", vfx = { "bossSlam", "confetti" } })`), and changing one never breaks another: - `Juice.remove(name) -> boolean` removes a preset you defined (false when there was none). Presets built on it keep working exactly as before: each keeps its own copy of the pieces it took from it. - Redefining a preset changes what the presets built on it play, except for a piece the new version no longer has: those keep the piece they had. - `define` and `remove` refuse a change that would leave another preset broken, such as two presets naming each other in a loop. They raise `juiceKit.define: 'a' would break 'b': …` (or `'a': …` when `a` itself would break), and every preset stays as it was. ### Settings | call | what it does | |---|---| | `Juice.setLook(name)` / `getLook()` / `looks()` / `hasLook(name)` / `vfxKinds()` | The one look switch every effect follows. | | `Juice.setIntensity(x)` / `getIntensity()` | Global intensity, clamped to 0–2. It scales shake, flash, hitstop and squash strength and effect density; 0 turns the kit off. | | `Juice.setReduceMotion(on)` / `getReduceMotion()` | Motion-sickness comfort: no camera shake at all, and gentler, shorter flashes. Hitstop, squash and effects still play. | | `Juice.stats()` | Counters and live counts from every piece, plus `recent`, the last 12 plays and receives with who got the personal parts, for HUDs, tests and debugging. | Settings are per peer, so each player chooses their own look, intensity and comfort. ## Multiplayer The world is always multiplayer, and `play` routes each piece for you. Every preset is made of two kinds of parts: - **World parts** happen at a spot: the visual effect, the squash, a blast shake (one with distance falloff), a blast flash (one with a radius) and a blast's hitstop. For a `world`-scope preset they run here and on every other peer. Each peer works out **its own** shake, flash and freeze from **its own** distance to the spot. A far player sees the blast without being shaken. Only players within roughly the inner third of the shake's range freeze. - **Personal parts** belong to one player's screen: a fixed camera shake, a screen flash and a hitstop. They play for **exactly one player**, never for everyone: | target | who gets the personal parts | |---|---| | nil, or your own avatar | you | | another player's avatar | only that player (it is sent to them) | | a thing (an NPC, a prop) or a point | you, or the attacking player when `opts.from` is another player's avatar | | a thing or a point, for a preset with `personal = "player"` | nobody: these moments only make sense for a player | The presets with `personal = "player"` are `hurt`, `heal`, `death`, `levelUp` and `landingHard`. A healer never sees the healed player's green pulse, and a killer never gets the victim's blackout. A hit (`hitLight`, `hitHeavy`, `hitCritical`) on an NPC lands on the attacker's screen; on another player it lands on theirs. - **Squash on a shared object**: a synced entity owned by another peer is squashed by its owner, who receives the same play, and its scale reaches everyone from there. Peers never write to an entity they don't own. - `scope = "local"` plays here only what belongs on this peer and sends nothing. Use it from code that already runs on every peer (for example, reacting to a synced health field): each peer then gets exactly its own share. - `Juice.stats().recent` shows, for the last few plays and receives, who got the personal parts (`"here"`, `"nobody"` or the recipient avatar's id) and what ran. - **Stopping travels like playing:** `Juice.stop` on a play this peer sent also sends a small stop message, and each peer that received the play stops exactly that one (matched by sender and play id). Stopping by name stops received plays of that name on your own screen only. A peer on a version before 1.1.2 ignores the stop and lets its share finish. ## Guarantees - **No camera drift:** the shake is added after every camera controller has run and removed before they run again. Measured on all nine builtin controllers (orbital follow, third person follow, first person, orbit, chase, side scroller, bird's eye, isometric and RTS): the camera returns to exactly where it would have been (0.000000 m of drift). - **Hitstop never sticks:** it is one owned time-scale hold. The slowest live request wins, and every span is capped (no freeze longer than 0.6 s). It always releases on end, on `stopAll`, on interruption and on reload. - **Cheap and self-cleaning:** particles are pooled instanced draws, capped at 700 live, with the oldest stolen first. Lights come from a pool of 4. Nothing is spawned per particle, and everything drains to zero and idles when quiet. - **Flashes are part of the picture:** they are drawn by one post-process pass over the lit scene, before the UI, so your HUD stays on top and untinted. The pass is switched off whenever no flash is playing. A copy of the module left behind by a hot reload can never switch it back on. - **Never touches the editor:** the shake only moves the gameplay camera in play mode, never the editor's fly-camera. A peer drops plays sent by other peers until its own scene has arrived. ## Pieces (for advanced use) The `juice` module is the front door. The modules under it can be used directly: | module | what it holds | |---|---| | `juiceKit.shake` | Additive camera shake layers (noise, kick, rumble, quake) with distance falloff. | | `juiceKit.hitstop` | Owned, capped time-scale holds. | | `juiceKit.flash` | Full-screen flashes, vignettes and glows, drawn into the rendered picture by one post-process pass under the UI. | | `juiceKit.squash` | Squash-and-stretch springs that always return to the base scale. | | `juiceKit.vfx` | Pooled particle effects: 12 kinds in 4 looks. | | `juiceKit.net` | The `juiceKit.play` message channel. | | `juiceKit.presets` | The data: presets, looks, palettes and effect recipes. | | `juiceKit.util` | Small vector, quaternion and targeting helpers. | Components: **JuiceNet** (optional; listens from scene load and sets the starting look), **JuiceShakeApply** and **JuiceShakeRestore** (attached to the camera automatically). Assets: `juiceParticle.shader`, `juiceFlash.shader` and the `juiceSolid`, `juiceGlow` and `juiceSmoke` materials. ## Tests Run them the standard way, in edit mode: `tools.use("tests", "run", "juiceKit")` (the shell form is `zero tests run juiceKit`). The suite is named `juiceKit`, not `juiceKit.testSuite`. You can also run it directly with `asset.resolve("juiceKit.juiceKit", "testSuite"):run()`. 104 tests cover every public call. They pass on repeated runs, either way, with or without a player or a scene camera: - **Playing:** every target form, and exactly what a play reports. - **Listing:** every filter, the sort order, and the copies `list` and `get` hand out. - **Defining your own presets:** broken specs are refused, defaults are worked out, redefining replaces, and presets build on presets. - **Presets built on presets:** removing or redefining a base keeps its dependents playing the same thing, a chain survives losing its root and then its middle, and loops are refused with the old preset intact. - **Looks:** each look's material and shape, and a look given to one play. - **Intensity:** flash alpha, shake strength, particle count and hitstop length. - **Reduce motion:** no shake, gentler flashes. - **Stopping early:** `stopAll` mid-shake, mid-hitstop, mid-squash, mid-flash and mid-effect. - **Stopping one play:** `Juice.stop` and `Juice.isPlaying` by result, id and name. Tested per piece (one shake, hitstop, flash, squash or effect stopped while another keeps going) and on whole combos, and a stop sent to and received from another peer reaches only that play. - **Multiplayer routing:** another player's flash and hitstop never land on the caller, blasts are scaled by distance, and squash is left to the owner. ## Watch out for - **Play from code every peer runs, or from one peer with the default scope.** By default (`scope = "auto"`) `play` sends the world parts to everyone. If the same call already runs on every peer (for example, a reaction to a synced health value), pass `scope = "local"`, or each peer receives it once per sender. - **Shakes only move the camera in play mode.** In edit mode `Juice.play` still runs the effects, flashes and squashes, but it never touches the editor's fly-camera. - **The flash is a post-process pass.** It tints the scene camera's picture, under your UI. If you want a flash *over* the UI (a menu fade), use a UI screen instead. The pass also tints offscreen captures and render-to-texture cameras taken while a flash plays, and clamps highlights brighter than white for that moment. - **Heavy scenes slow down joiners.** Every entity a scene bakes in is replicated in play, and a joining peer receives them all as one snapshot before its gameplay starts. Keep static scenery light, or spawn it from code each peer runs, so new players get in quickly. - **Reduce motion is per peer.** It is a comfort setting for the player at this screen. Set it from that player's own options, not from shared state. - **Give every joiner a start view of your own.** A player prototype's camera rig is `OwnerOnly`, so a joiner whose player was spawned on another peer receives the body and no camera. The showroom's Gallery shows one way to handle it: it gives that player a local follow camera, and works out the starting heading from the spawn and the stage rather than from the body. - **Testing with the standard runner.** `tests.run` runs a suite in edit mode with no avatar, an empty scene and fallback lighting, and in edit mode the camera on screen is the editor's. The kit's "where am I" (`U.herePos`) falls back from the avatar to the gameplay camera, then to the camera on screen, then to the world origin, so the suite passes either way. The runner takes the suite's asset name: `juiceKit`, not `juiceKit.testSuite`. - **A second player needs a second client.** Two agent sessions in one engine (`play as <name>`) are one peer, so a real two-player check needs another desktop session or the web, ideally signed in to another account (see #14448). - **Small API traps.** `entity.exists` raises when given a live entity's name, so pass an id. `_G` is sealed. A local named after an engine namespace (`live`, `av`) hides that namespace. ## Known issues These are engine problems met while building the kit or the showroom, each with its engine issue number. The kit or the showroom works around each one where it can; they are listed so a creator who meets one knows what it is. - **No character is drawn on a joining player's screen** (#16913, #14448). In a two-session test, the player who joined saw neither their own character nor the other player's. Another player's avatar arrives with no visible body (#16913), and two sessions signed in to the same account are mishandled when the second one joins (#14448). The showroom still gives the joiner a working view and HUD, and every effect still plays for them. - **A joining player in a session with no window gets no view** (#19169). Run two-player checks with two windowed sessions. - **A one-shot particle burst `.effect` fails to build** (#19206). The kit draws its effects with its own pooled particles instead, so nothing in the kit depends on it. - **A test clean-up hook registered outside a group is dropped** (#12497). A top-level `Test.afterEach` never runs, so each `describe` in the kit's suite installs its own clean-up. - **A follow camera binding to a body whose look has not loaded starts in front of it** (#19313). The orbital follow camera takes its heading from the body's facing when it binds. A body that has not loaded yet reports the default facing, so the camera lands in front of the player looking away. The showroom sets the heading itself for the first moments after a player appears. - **Harmless `asset-unresolved` warnings** (#12937). The code checker reports them for `~.JuiceShakeApply`, `~.JuiceShakeRestore`, `~.juiceSolid`, `~.juiceGlow`, `~.juiceSmoke` and `~.juiceFlash`; they all resolve when running.