dicEx

Pixel-art 3D dice roller for Phoenix LiveView

dicEx computes D&D-style dice rolls in pure Elixir and pairs them with a Three.js + Rapier physics visualization that drops into any LiveView as a component or modal. The rolls are seedable and testable; the tumbling dice are theatre that settle naturally without a post-roll correction spin.

Two reveal modes, both computed through Elixir so modifiers always apply:

• 2D engine — the server roll is the source of truth; the visible tumble lands exactly on the value Elixir decided.
• 3D engine — physics is truth: the dice land where Rapier takes them and the landed faces are reported back, so what you see is what happened.

Features

• Full dice notation — 3d6, 2d20kh1 (advantage), 4d6dl1 (ability scores), 8d6! (explode), 1d20r1 (reroll), 1d20+5.
• Deterministic & seedable — replay rolls, anti-cheat, golden-path tests.
• Structured results — %DicEx.Result{} with per-die outcomes, kept/dropped flags, and a JSON-friendly to_map/1 for LLM consumption.
• 3D pixel-art dice — low-poly d4/d6/d8/d10/d12/d20 with procedurally drawn bitmap-font textures and real Rapier physics.
• Drop-in LiveView component — inline or modal, themed (obsidian / arcane / dnd).
• No web dependency required for the core — phoenix_live_view (+ jason) are optional; only needed for the component.

Installation

Add dic_ex to your mix.exs:

def deps do
  [
    {:dic_ex, "~> 0.1.0"}
  ]
end

Then:

mix deps.get
mix dic_ex.install   # copies dic_ex.min.js -> assets/vendor, dic_ex.css -> assets/css

Core usage (pure Elixir)

DicEx.roll("1d20")           # => %DicEx.Result{total: 14, ...}
DicEx.roll("3d6 + 2")        # => %DicEx.Result{total: 13, ...}
DicEx.roll("2d20kh1")        # advantage — keep highest
DicEx.roll("4d6dl1")         # 4d6, drop lowest
DicEx.roll("8d6!")           # explode (fireball)
DicEx.roll("1d20r1")         # reroll natural 1s

# safe variant for untrusted/LLM-generated expressions
{:ok, result} = DicEx.roll_e(prompted_by_the_llm)

# programmatic API matching a UI's "count + die + modifier"
DicEx.roll_dice(2, 20, mod: 5, advantage: true)

# reproducible
DicEx.roll("4d6", seed: 42)

Structured result

%DicEx.Result{
  expression: "2d20kh1 + 5",
  total: 23,
  groups: [
    %{kind: :dice, notation: nil, sides: 20, subtotal: 18, modifiers: [{:keep_high, 1}],
      rolls: [%{value: 18, kept: true, exploded: false}, %{value: 7, kept: false, exploded: false}]},
    %{kind: :modifier, notation: nil, sides: nil, subtotal: 5, modifiers: [], rolls: []}
  ]
}

DicEx.Result.to_map(result)   # JSON-ready map for your LLM / client

The per-group notation is left nil; the full expression lives on the top-level expression field.

Notation reference

LiveView component

1. Import the assets into your bundle (Phoenix 1.8+ only serves app.js / app.css, so dicEx ships as vendored imports, not external tags):

// assets/js/app.js
import "../vendor/dic_ex.min.js"        // sets window.DicExHooks

const hooks = { ...(window.DicExHooks || {}) }
const liveSocket = new LiveSocket("/live", Socket, { hooks, /* ... */ })

/* assets/css/app.css — after the tailwind import */
@import "./dic_ex.css";

mix dic_ex.install copies dic_ex.min.js → assets/vendor/ and dic_ex.css → assets/css/ and prints the exact wiring.

1. Drop the component anywhere — inline or in a modal:

<.live_component module={DicExWeb.DiceRoller} id="dice-roller" />

Receiving rolls

Pass on_roll: self() and the host LiveView is notified with the full result, ready to hand to an AI game master or any other consumer:

<.live_component module={DicExWeb.DiceRoller} id="roller" on_roll={self()} />

def handle_info({:dic_ex_rolled, %{result: result, component: id}}, socket) do
  # result is a %DicEx.Result{} — feed its JSON map to the LLM
  {:noreply, socket}
end

Options

Building assets from source

The package ships prebuilt assets. To rebuild after editing assets/src:

mix dic_ex.build     # bundles Three.js + Rapier -> priv/static/dic_ex.min.js

Requires Node.js + a JS package manager (pnpm/bun/npm; the build task installs deps automatically on first run).

Architecture

dic_ex/
├── lib/dic_ex.ex                  # public API: roll/2, roll_dice/3, format/1
├── lib/dic_ex/                    # core: parser, roller, dice, result, rng
├── lib/dic_ex_web/                # LiveView component (guarded: needs LiveView)
├── lib/mix/tasks/                 # mix dic_ex.build, mix dic_ex.install
├── assets/src/                    # Three.js + Rapier scene, dice factory, hook
└── priv/static/                   # prebuilt dic_ex.min.js + dic_ex.css

The roll is computed through Elixir for both engines. The 2D hook receives the server result via push_event("dic_ex:roll", ...), tumbles the dice, and reveals it in sync. The 3D hook throws the dice physically and, once they settle, reports the landed faces back (dic_ex:landed) so Elixir recomputes the result around the physics outcome — modifiers (kh/dl/explode…) still apply, and the revealed total matches exactly what landed on the table.

License

MIT