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# Avatar Component System & glTF Attachment Spec
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> **Status:** Proposed
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> **Owner:** Platform team
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> **Related:** Server authority + client prediction, world chunk data format
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## 1. Overview
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This document specifies the **avatar component system** for **agp-game**, a
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Godot-based multiplayer game. It defines:
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- How an avatar is decomposed into **body parts** and **attachment slots**.
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- How **cosmetic attachments** (clothing, accessories, gear) mount onto the
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base body.
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- The **glTF/GLB format requirements** that all avatar assets must satisfy so
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they can be loaded, skinned, and networked consistently.
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The goal is a **modular, data-driven avatar pipeline**: a single base body rig
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plus swappable attachments, all authored in glTF and consumed by a shared Godot
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runtime. This enables player customization, cosmetic monetization, and
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server-authoritative validation of what a player is wearing.
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### 1.1 Design Goals
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- **Modularity:** Body parts and attachments are independent assets that can be
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combined at runtime without re-exporting.
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- **Consistency:** A single, well-defined skeleton and slot convention so any
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attachment fits any base body.
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- **Networkability:** The avatar's composition is expressed as a compact,
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serializable **loadout** that the server can validate and replicate.
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- **Performance:** Attachments are skinned to the same skeleton and share
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materials where possible to minimize draw calls and skinning cost.
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- **Tooling-friendly:** Assets are authored in standard glTF 2.0 and validated
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by a build-time checker.
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---
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## 2. Avatar Decomposition
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### 2.1 The Base Body
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Every avatar is built on a **base body** — a single glTF asset containing:
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- A **skeleton** (the canonical rig, see §3).
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- A **base mesh** for the skin/body (head, torso, arms, legs).
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- **Attachment points** (empty nodes) that define where accessories mount.
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The base body is the only asset that carries the skeleton. Attachments reference
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the skeleton by **bone name** and are skinned to it; they never carry their own
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rig.
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### 2.2 Body Parts vs. Attachments
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Two distinct concepts:
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| Concept | Definition | Example |
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|----------------|-------------------------------------------------------------------------|----------------------------------|
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| **Body part** | A mesh that replaces part of the base body's skin (e.g., a different head, a tail, wings). | Alternate head, cybernetic arm |
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| **Attachment** | A mesh that mounts *on top of* the body without replacing it (clothing, accessories). | Shirt, hat, glasses, backpack |
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The distinction matters for **slot exclusivity** and **layering**:
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- **Body parts** are *exclusive* per slot — only one head can be equipped.
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- **Attachments** are *layered* — a hat and glasses can coexist, and both sit
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above the head mesh.
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---
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## 3. Skeleton & Slot Convention
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||||||
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### 3.1 Canonical Skeleton
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All avatars share a **canonical skeleton** with a fixed set of bone names. This
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is the contract that lets any attachment fit any body. The skeleton follows a
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humanoid convention (Godot's `Humanoid` profile / glTF VRM-style naming).
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Required bones (subset of the full rig):
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```
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Root
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├── Hips
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│ ├── Spine
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│ │ ├── Chest
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│ │ │ ├── Neck
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│ │ │ │ └── Head
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│ │ │ │ ├── HeadTop # hat / hair mount
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│ │ │ │ ├── Jaw # face accessories
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│ │ │ │ └── LeftEye / RightEye
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│ │ │ ├── LeftShoulder
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│ │ │ │ └── LeftUpperArm
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│ │ │ │ └── LeftLowerArm
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│ │ │ │ └── LeftHand
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│ │ │ └── RightShoulder
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│ │ │ └── RightUpperArm
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│ │ │ └── RightLowerArm
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│ │ │ └── RightHand
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│ │ └── (Chest children for torso attachments)
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│ ├── LeftUpperLeg
|
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│ │ └── LeftLowerLeg
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│ │ └── LeftFoot
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│ └── RightUpperLeg
|
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│ └── RightLowerLeg
|
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│ └── RightFoot
|
||||||
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```
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**Rules:**
|
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|
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- Bone names are **case-sensitive** and must match exactly.
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- The skeleton is **T-pose** at rest for consistent skinning.
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- Attachments must be skinned to **at least** the bones they deform; static
|
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accessories may be parented to a single bone (e.g., a hat parented to `Head`).
|
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### 3.2 Attachment Slots
|
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Slots are the **logical mount points** for body parts and attachments. Each slot
|
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maps to one or more bones and defines what can be equipped there.
|
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|
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| Slot ID | Category | Mount bone(s) | Exclusivity | Example assets |
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|----------------|--------------|--------------------|-------------|-------------------------------|
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| `head` | body part | `Head` | exclusive | alternate head, face |
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| `hair` | attachment | `HeadTop` | exclusive | hairstyles, hats |
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| `face` | attachment | `Jaw` | exclusive | glasses, masks, beards |
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| `torso` | body part | `Chest` | exclusive | alternate torso |
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| `chest` | attachment | `Chest` | exclusive | shirts, armor, chest gear |
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| `back` | attachment | `Chest` (back) | exclusive | backpacks, wings, capes |
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| `left_arm` | body part | `LeftUpperArm` | exclusive | alternate arm |
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| `right_arm` | body part | `RightUpperArm` | exclusive | alternate arm |
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| `left_hand` | attachment | `LeftHand` | exclusive | gloves, weapons (held) |
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| `right_hand` | attachment | `RightHand` | exclusive | gloves, weapons (held) |
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| `legs` | body part | `Hips` | exclusive | alternate legs |
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| `pants` | attachment | `Hips` | exclusive | pants, skirts |
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| `left_foot` | attachment | `LeftFoot` | exclusive | shoes |
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| `right_foot` | attachment | `RightFoot` | exclusive | shoes |
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| `accessory` | attachment | `Root` (free) | multiple | belts, jewelry, floating items|
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**Slot semantics:**
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- **`exclusive`** slots allow at most one equipped item at a time.
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- The **`accessory`** slot is *multi-slot* — multiple accessories may be equipped
|
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simultaneously (bounded by a configurable limit, e.g., 8).
|
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- **Body-part slots** (`head`, `torso`, `legs`, `left_arm`, `right_arm`) replace
|
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the corresponding base mesh. When a body part is equipped, the base mesh for
|
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that region is hidden.
|
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- **Attachment slots** layer on top of the base mesh and never hide it.
|
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### 3.3 Slot → Bone Mapping
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|
||||||
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Each slot declares a **primary mount bone** and an optional **secondary bone
|
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list** for skinning. The runtime uses this to:
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1. Parent static accessories to the mount bone.
|
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2. Skin skinned attachments to the union of the slot's bones.
|
||||||
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|
||||||
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---
|
||||||
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|
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## 4. glTF/GLB Format Requirements
|
||||||
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|
||||||
|
All avatar assets (base bodies, body parts, attachments) are distributed as
|
||||||
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**glTF 2.0** (`.gltf` + external buffers/textures) or **GLB** (`.glb`, binary
|
||||||
|
container). GLB is the preferred distribution format for runtime loading.
|
||||||
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|
||||||
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### 4.1 Required Conventions
|
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| Concern | Requirement |
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|--------------------|------------------------------------------------------------------------------|
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||||||
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| **Format** | glTF 2.0 (`.gltf` or `.glb`). GLB preferred for runtime. |
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| **Coordinate system** | glTF standard: **+Y up, +Z forward, right-handed**. Godot converts to its own convention on import. |
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| **Units** | Meters. Avatar height ~1.8 m at the `Root` bone. |
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| **Skeleton** | Single skeleton per asset; bone names per §3.1. |
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| **Skinning** | `skins` + `nodes` with `JOINTS_0` / `WEIGHTS_0` accessors. |
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| **Pose** | T-pose at rest. |
|
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| **Materials** | PBR metallic-roughness. Use `KHR_materials_unlit` for emissive/UI-only items. |
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||||||
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| **Textures** | Max 2048×2048; power-of-two preferred. Use `KHR_texture_basisu` (BasisU) for runtime. |
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| **Animation** | Optional. If present, must not rename or remove canonical bones. |
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### 4.2 Asset Metadata (extras)
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||||||
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|
||||||
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Each asset **must** declare its slot and identity in the glTF `asset.extras`
|
||||||
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object. This is the machine-readable contract consumed by the build pipeline and
|
||||||
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runtime.
|
||||||
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|
||||||
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```json
|
||||||
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{
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||||||
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"asset": {
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"version": "2.0",
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||||||
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"extras": {
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||||||
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"agp": {
|
||||||
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"type": "attachment", // "base_body" | "body_part" | "attachment"
|
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"slot": "chest", // slot ID from §3.2
|
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"id": "shirt_bandit_01", // globally unique asset id
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||||||
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"display_name": "Bandit Shirt",
|
||||||
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"version": "1.0.0",
|
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"mount_bone": "Chest", // primary mount bone
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||||||
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"skin_bones": ["Chest", "Spine", "LeftUpperArm", "RightUpperArm"],
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"exclusive": true, // matches slot exclusivity
|
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"tags": ["cloth", "common"],
|
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"author": "platform-team"
|
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|
}
|
||||||
|
}
|
||||||
|
}
|
||||||
|
}
|
||||||
|
```
|
||||||
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|
||||||
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**Validation rules for `extras.agp`:**
|
||||||
|
|
||||||
|
- `type` must be one of `base_body`, `body_part`, `attachment`.
|
||||||
|
- `slot` must be a known slot ID (§3.2).
|
||||||
|
- `mount_bone` must exist in the canonical skeleton.
|
||||||
|
- `skin_bones` must all exist in the canonical skeleton.
|
||||||
|
- `exclusive` must match the slot's declared exclusivity.
|
||||||
|
- `id` must be unique across the asset catalog.
|
||||||
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|
||||||
|
### 4.3 Node Naming Convention
|
||||||
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|
||||||
|
To make assets self-describing and mergeable, nodes follow a convention:
|
||||||
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|
||||||
|
- **Base body:** the mesh node is named `Body`; the skeleton root is `Root`.
|
||||||
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- **Body part:** the mesh node is named `<SlotID>_Mesh` (e.g., `head_Mesh`).
|
||||||
|
- **Attachment:** the mesh node is named `<SlotID>_<AssetID>` (e.g.,
|
||||||
|
`chest_shirt_bandit_01`).
|
||||||
|
- **Attachment points** (empty nodes) on the base body are named
|
||||||
|
`attach_<slot>` (e.g., `attach_head`, `attach_left_hand`).
|
||||||
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|
||||||
|
### 4.4 Material & Texture Requirements
|
||||||
|
|
||||||
|
- All materials use the **metallic-roughness** PBR model.
|
||||||
|
- Textures are embedded in the GLB or referenced as external files; external
|
||||||
|
references must be relative paths within the asset package.
|
||||||
|
- **Color customization** is supported via a `baseColorFactor` tint applied at
|
||||||
|
runtime (multiplied over the albedo). Assets should use a neutral albedo
|
||||||
|
(white/gray) where tinting is intended.
|
||||||
|
- **Masked/transparent** materials must set the correct alpha mode
|
||||||
|
(`MASK` or `BLEND`) and `alphaCutoff`.
|
||||||
|
|
||||||
|
### 4.5 Skeleton Merging at Runtime
|
||||||
|
|
||||||
|
When an attachment is loaded, the runtime **merges** it onto the base body:
|
||||||
|
|
||||||
|
1. Load the base body (skeleton + base meshes).
|
||||||
|
2. Load each equipped attachment.
|
||||||
|
3. For each attachment, **re-target its skin** to the base body's skeleton by
|
||||||
|
bone name (no re-export needed).
|
||||||
|
4. Parent static accessories to their `mount_bone`.
|
||||||
|
5. Hide base meshes for any equipped body-part slots.
|
||||||
|
6. Apply material tints and merge into the render tree.
|
||||||
|
|
||||||
|
The merge is **name-based** — bone names must match exactly (§3.1). This is the
|
||||||
|
core reason for the strict naming contract.
|
||||||
|
|
||||||
|
---
|
||||||
|
|
||||||
|
## 5. Loadout Model (Network & Persistence)
|
||||||
|
|
||||||
|
The avatar's composition is serialized as a **loadout** — a compact, ordered
|
||||||
|
list of equipped asset IDs. This is what the server validates, persists, and
|
||||||
|
replicates.
|
||||||
|
|
||||||
|
### 5.1 Loadout JSON
|
||||||
|
|
||||||
|
```json
|
||||||
|
{
|
||||||
|
"base_body": "base_human_male_01",
|
||||||
|
"slots": {
|
||||||
|
"head": "head_cyber_01",
|
||||||
|
"hair": "hair_mohawk_01",
|
||||||
|
"face": null,
|
||||||
|
"torso": null,
|
||||||
|
"chest": "chest_bandit_01",
|
||||||
|
"back": "backpack_01",
|
||||||
|
"left_arm": null,
|
||||||
|
"right_arm": null,
|
||||||
|
"left_hand": "glove_leather_01",
|
||||||
|
"right_hand": "glove_leather_01",
|
||||||
|
"legs": null,
|
||||||
|
"pants": "pants_cargo_01",
|
||||||
|
"left_foot": "shoe_boot_01",
|
||||||
|
"right_foot": "shoe_boot_01",
|
||||||
|
"accessory": ["belt_01", "necklace_01"]
|
||||||
|
}
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
**Rules:**
|
||||||
|
|
||||||
|
- `base_body` is required and must reference a valid `base_body` asset.
|
||||||
|
- Each exclusive slot holds **at most one** asset id (or `null`).
|
||||||
|
- `accessory` is an array (0..N, bounded).
|
||||||
|
- The server validates that every id exists in the catalog and that slot
|
||||||
|
exclusivity is respected.
|
||||||
|
|
||||||
|
### 5.2 Network Replication
|
||||||
|
|
||||||
|
The loadout is replicated as part of the player's spawn/state data:
|
||||||
|
|
||||||
|
```
|
||||||
|
spawn_entity:
|
||||||
|
entity_id: uint32
|
||||||
|
type: player
|
||||||
|
transform: { x, y, rot }
|
||||||
|
props:
|
||||||
|
loadout_hash: uint32 # hash of the loadout for change detection
|
||||||
|
loadout: { ... } # full loadout on spawn / on change
|
||||||
|
```
|
||||||
|
|
||||||
|
- The **full loadout** is sent on spawn and whenever it changes (reliable).
|
||||||
|
- A **`loadout_hash`** lets clients skip re-resolving assets if unchanged.
|
||||||
|
- The server is the **authority** on the loadout; clients send *requests* to
|
||||||
|
change equipment, and the server validates and broadcasts the result.
|
||||||
|
|
||||||
|
### 5.3 Server-Side Validation
|
||||||
|
|
||||||
|
The server rejects a loadout if:
|
||||||
|
|
||||||
|
- `base_body` is missing or unknown.
|
||||||
|
- Any slot references an unknown asset id.
|
||||||
|
- An exclusive slot has more than one item.
|
||||||
|
- An asset's declared `slot` does not match the slot it is placed in.
|
||||||
|
- The accessory list exceeds the configured limit.
|
||||||
|
- The asset is not owned/unlocked by the player (for gated cosmetics).
|
||||||
|
|
||||||
|
---
|
||||||
|
|
||||||
|
## 6. Godot Runtime Architecture
|
||||||
|
|
||||||
|
### 6.1 Node Structure
|
||||||
|
|
||||||
|
```
|
||||||
|
Avatar (Node3D)
|
||||||
|
├── Skeleton3D # canonical skeleton (from base body)
|
||||||
|
├── BodyMeshes # base body meshes (skinned to Skeleton3D)
|
||||||
|
│ ├── head_Mesh
|
||||||
|
│ ├── torso_Mesh
|
||||||
|
│ └── ...
|
||||||
|
├── Attachments # equipped attachments
|
||||||
|
│ ├── chest_shirt_bandit_01
|
||||||
|
│ ├── hair_mohawk_01
|
||||||
|
│ └── ...
|
||||||
|
└── AttachmentPoints # empty nodes for dynamic mounting
|
||||||
|
├── attach_head
|
||||||
|
├── attach_left_hand
|
||||||
|
└── ...
|
||||||
|
```
|
||||||
|
|
||||||
|
### 6.2 Core Classes
|
||||||
|
|
||||||
|
| Class | Responsibility |
|
||||||
|
|--------------------------|-------------------------------------------------------------|
|
||||||
|
| `AvatarSystem` | Loads base body + attachments, resolves loadouts, owns the avatar node. |
|
||||||
|
| `AvatarLoader` | glTF/GLB import, skeleton merge, skin re-targeting. |
|
||||||
|
| `AvatarSlotRegistry` | Static registry of slot definitions (id, bones, exclusivity).|
|
||||||
|
| `AvatarLoadout` | Serializable loadout model + validation. |
|
||||||
|
| `AvatarCatalog` | Asset catalog (id → asset metadata + resource path). |
|
||||||
|
| `AvatarVisualizer` | Builds the render tree from a loadout. |
|
||||||
|
|
||||||
|
### 6.3 Loading Pipeline
|
||||||
|
|
||||||
|
```
|
||||||
|
loadout JSON
|
||||||
|
│
|
||||||
|
▼
|
||||||
|
AvatarCatalog.resolve(loadout) # id → asset metadata + GLB path
|
||||||
|
│
|
||||||
|
▼
|
||||||
|
AvatarLoader.load_base_body() # import GLB, extract skeleton + base meshes
|
||||||
|
│
|
||||||
|
▼
|
||||||
|
for each equipped slot:
|
||||||
|
AvatarLoader.load_attachment()# import GLB, re-target skin to skeleton
|
||||||
|
│
|
||||||
|
▼
|
||||||
|
AvatarVisualizer.assemble() # parent, hide replaced parts, apply tints
|
||||||
|
│
|
||||||
|
▼
|
||||||
|
Avatar node ready for render
|
||||||
|
```
|
||||||
|
|
||||||
|
### 6.4 Performance Considerations
|
||||||
|
|
||||||
|
- **Shared skeleton:** All meshes skin to one `Skeleton3D`, so skinning is
|
||||||
|
computed once per frame.
|
||||||
|
- **Material batching:** Attachments that share a material are merged into a
|
||||||
|
single mesh where possible (static accessories).
|
||||||
|
- **LOD:** Optional LOD variants per asset; the runtime selects based on
|
||||||
|
distance.
|
||||||
|
- **Caching:** Resolved loadouts and imported GLB resources are cached by
|
||||||
|
`AvatarCatalog` to avoid re-importing on respawn or re-join.
|
||||||
|
|
||||||
|
---
|
||||||
|
|
||||||
|
## 7. Asset Pipeline & Validation
|
||||||
|
|
||||||
|
### 7.1 Build-Time Validation
|
||||||
|
|
||||||
|
A build-time checker validates every asset before it enters the catalog:
|
||||||
|
|
||||||
|
1. **Format check:** valid glTF 2.0 / GLB.
|
||||||
|
2. **Metadata check:** `extras.agp` present and valid (§4.2).
|
||||||
|
3. **Skeleton check:** all `skin_bones` exist in the canonical skeleton.
|
||||||
|
4. **Slot check:** `slot` is known and `exclusive` matches.
|
||||||
|
5. **Mesh check:** meshes are skinned (or static accessories parented to a bone).
|
||||||
|
6. **Texture check:** sizes, formats, and alpha modes are valid.
|
||||||
|
7. **Uniqueness check:** `id` is unique.
|
||||||
|
|
||||||
|
### 7.2 Catalog Manifest
|
||||||
|
|
||||||
|
The catalog is a JSON manifest mapping asset ids to metadata and resource paths:
|
||||||
|
|
||||||
|
```json
|
||||||
|
{
|
||||||
|
"assets": {
|
||||||
|
"base_human_male_01": {
|
||||||
|
"type": "base_body",
|
||||||
|
"path": "res://assets/avatars/base_human_male_01.glb",
|
||||||
|
"version": "1.0.0"
|
||||||
|
},
|
||||||
|
"chest_bandit_01": {
|
||||||
|
"type": "attachment",
|
||||||
|
"slot": "chest",
|
||||||
|
"path": "res://assets/avatars/chest_bandit_01.glb",
|
||||||
|
"version": "1.0.0"
|
||||||
|
}
|
||||||
|
}
|
||||||
|
}
|
||||||
|
```
|
||||||
|
|
||||||
|
---
|
||||||
|
|
||||||
|
## 8. Security & Anti-Cheat
|
||||||
|
|
||||||
|
- **Server-authoritative loadouts:** Clients only *request* equipment changes;
|
||||||
|
the server validates against the catalog and the player's owned items.
|
||||||
|
- **No client asset injection:** Clients cannot send arbitrary GLB data; they
|
||||||
|
reference catalog ids only.
|
||||||
|
- **Rate limiting:** Equipment-change requests are rate-limited per peer.
|
||||||
|
- **Hash verification:** The `loadout_hash` lets the server detect tampered or
|
||||||
|
stale loadout state.
|
||||||
|
|
||||||
|
---
|
||||||
|
|
||||||
|
## 9. Open Questions / Future Work
|
||||||
|
|
||||||
|
- **Morph targets / blendshapes:** Support for facial expressions and body
|
||||||
|
morphs (e.g., height, muscle) via glTF morph targets.
|
||||||
|
- **Physics attachments:** Cloth simulation for capes/skirts (Godot cloth).
|
||||||
|
- **Dynamic tinting UI:** A color-picker that writes `baseColorFactor` tints.
|
||||||
|
- **VRM compatibility:** Consider supporting VRM (a glTF extension for
|
||||||
|
humanoid avatars) as an import source.
|
||||||
|
- **Attachment LOD streaming:** Streaming high-res attachments on demand.
|
||||||
|
|
||||||
|
---
|
||||||
|
|
||||||
|
## 10. Summary
|
||||||
|
|
||||||
|
| Concern | Decision |
|
||||||
|
|------------------------|-------------------------------------------------------|
|
||||||
|
| Format | glTF 2.0 / GLB (GLB preferred for runtime) |
|
||||||
|
| Skeleton | Single canonical humanoid skeleton, name-based merge |
|
||||||
|
| Slots | Fixed slot registry; exclusive body parts + layered attachments |
|
||||||
|
| Loadout | Compact JSON; server-authoritative and validated |
|
||||||
|
| Replication | Full loadout on spawn/change + `loadout_hash` |
|
||||||
|
| Runtime | Godot `Skeleton3D` + name-based skin re-targeting |
|
||||||
|
| Validation | Build-time asset checker + runtime catalog validation |
|
||||||
@@ -0,0 +1,426 @@
|
|||||||
|
# Content Moderation & Age Verification Architecture
|
||||||
|
|
||||||
|
> **Status:** Proposed
|
||||||
|
> **Owner:** Platform team
|
||||||
|
> **Related:** Server authority + client prediction, avatar component system, backend auth (JWT)
|
||||||
|
|
||||||
|
## 1. Overview
|
||||||
|
|
||||||
|
This document specifies the **content moderation** and **age verification**
|
||||||
|
architecture for **agp-game**, a Godot-based multiplayer game built by
|
||||||
|
autonomous agents. It defines:
|
||||||
|
|
||||||
|
- How **content flags** propagate through the system across the three primary
|
||||||
|
content types: **assets**, **rooms**, and **scripts**.
|
||||||
|
- How flags are **evaluated, aggregated, and enforced** at load time, at
|
||||||
|
runtime, and at the network boundary.
|
||||||
|
- The **age verification flow**, combining a lightweight **self-declaration**
|
||||||
|
with an optional **ID check hook** for higher-assurance verification.
|
||||||
|
|
||||||
|
The goal is a **single, consistent moderation pipeline** that applies the same
|
||||||
|
rules to user-generated content (UGC) regardless of whether it is a 3D asset, a
|
||||||
|
room definition, or a script, and that gates access to mature content behind a
|
||||||
|
verifiable age gate.
|
||||||
|
|
||||||
|
### 1.1 Design Goals
|
||||||
|
|
||||||
|
- **Uniformity:** One flag vocabulary and one propagation mechanism across
|
||||||
|
assets, rooms, and scripts.
|
||||||
|
- **Composability:** Flags on a room aggregate the flags of the assets and
|
||||||
|
scripts it contains; flags on a world aggregate the flags of its rooms.
|
||||||
|
- **Enforcement at the boundary:** The server is authoritative for what content
|
||||||
|
a client may load or receive, mirroring the server-authoritative networking
|
||||||
|
model.
|
||||||
|
- **Privacy-preserving age checks:** Self-declaration requires no PII; the ID
|
||||||
|
check hook is optional, pluggable, and never stores raw identity documents.
|
||||||
|
- **Auditability:** Every flag decision is logged with a reason, an actor, and
|
||||||
|
a timestamp so moderation actions are reviewable.
|
||||||
|
|
||||||
|
---
|
||||||
|
|
||||||
|
## 2. Content Flag Vocabulary
|
||||||
|
|
||||||
|
All content carries a set of **content flags**. A flag is a typed, immutable
|
||||||
|
label with a **severity** and a **scope**. Flags are the atomic unit of
|
||||||
|
moderation; everything else (aggregation, enforcement, gating) operates on
|
||||||
|
flags.
|
||||||
|
|
||||||
|
### 2.1 Flag Definition
|
||||||
|
|
||||||
|
A flag is a structured record:
|
||||||
|
|
||||||
|
| Field | Type | Description |
|
||||||
|
|------------|-----------|--------------------------------------------------------------------------|
|
||||||
|
| `id` | `string` | Stable machine-readable identifier, e.g. `violence.gore`. |
|
||||||
|
| `label` | `string` | Human-readable name, e.g. "Graphic Gore". |
|
||||||
|
| `category` | `enum` | One of `violence`, `sexual`, `language`, `substance`, `gambling`, `horror`, `hate`, `custom`. |
|
||||||
|
| `severity` | `enum` | One of `none`, `mild`, `moderate`, `severe`. |
|
||||||
|
| `scope` | `enum` | One of `visual`, `audio`, `text`, `behavior`, `interaction`. |
|
||||||
|
| `mature` | `bool` | Whether this flag triggers the age gate (see §5). |
|
||||||
|
| `reason` | `string` | Free-text justification supplied by the flagger. |
|
||||||
|
| `source` | `enum` | One of `author`, `moderator`, `automated`, `community`. |
|
||||||
|
|
||||||
|
### 2.2 Canonical Flag Set
|
||||||
|
|
||||||
|
The platform defines a **canonical registry** of flags so that different
|
||||||
|
content types and different flaggers use the same vocabulary. Examples:
|
||||||
|
|
||||||
|
| id | category | severity | scope | mature |
|
||||||
|
|-----------------------------|------------|-----------|--------------|--------|
|
||||||
|
| `violence.none` | violence | none | visual | false |
|
||||||
|
| `violence.mild` | violence | mild | visual | false |
|
||||||
|
| `violence.gore` | violence | severe | visual | true |
|
||||||
|
| `sexual.suggestive` | sexual | mild | visual | true |
|
||||||
|
| `sexual.explicit` | sexual | severe | visual | true |
|
||||||
|
| `language.mild` | language | mild | text | false |
|
||||||
|
| `language.profanity` | language | moderate | text | false |
|
||||||
|
| `substance.references` | substance | mild | text | false |
|
||||||
|
| `gambling.simulated` | gambling | moderate | behavior | true |
|
||||||
|
| `horror.jumpscare` | horror | mild | audio/visual | false |
|
||||||
|
| `hate.hateful` | hate | severe | text | true |
|
||||||
|
|
||||||
|
The registry is **data-driven** (a JSON/YAML manifest shipped with the server)
|
||||||
|
so new flags can be added without code changes.
|
||||||
|
|
||||||
|
---
|
||||||
|
|
||||||
|
## 3. Flag Propagation Model
|
||||||
|
|
||||||
|
Flags propagate through the system along the **content dependency graph**. The
|
||||||
|
three content types form a hierarchy:
|
||||||
|
|
||||||
|
```
|
||||||
|
World
|
||||||
|
└── Room
|
||||||
|
├── Asset (mesh, texture, audio, animation, material)
|
||||||
|
└── Script (behavior, dialogue, event logic)
|
||||||
|
```
|
||||||
|
|
||||||
|
### 3.1 Propagation Rules
|
||||||
|
|
||||||
|
1. **Explicit flags** are set directly on a content item by its author or a
|
||||||
|
moderator.
|
||||||
|
2. **Inherited flags** flow upward: a room's effective flag set is the **union**
|
||||||
|
of its own explicit flags and the flags of every asset and script it
|
||||||
|
references.
|
||||||
|
3. **Aggregation** uses the **maximum severity** per category across all
|
||||||
|
contributing items. A room containing one `violence.gore` asset and one
|
||||||
|
`violence.none` asset is `violence.severe`.
|
||||||
|
4. **Maturity is monotonic:** if any contributing item is `mature`, the
|
||||||
|
containing room and world are `mature`.
|
||||||
|
5. **Cycles are impossible** by construction: content references form a DAG
|
||||||
|
(an asset cannot contain a room; a room cannot contain itself).
|
||||||
|
|
||||||
|
### 3.2 Propagation Through the Pipeline
|
||||||
|
|
||||||
|
Flags are attached at **authoring time** and carried through every stage:
|
||||||
|
|
||||||
|
```
|
||||||
|
Authoring ──► Upload ──► Validation ──► Storage ──► Distribution ──► Runtime
|
||||||
|
│ │ │ │ │ │
|
||||||
|
│ flag │ flag │ automated │ flag │ flag │ flag
|
||||||
|
│ declared │ preserved │ scan adds │ indexed │ re-checked │ enforced
|
||||||
|
│ │ │ flags │ │ │
|
||||||
|
```
|
||||||
|
|
||||||
|
| Stage | Responsibility |
|
||||||
|
|--------------|-------------------------------------------------------------------------|
|
||||||
|
| **Authoring**| Author declares flags in the editor/upload UI. |
|
||||||
|
| **Upload** | Flags are validated against the canonical registry; unknown flags rejected. |
|
||||||
|
| **Validation**| Automated scanner (hash-based + heuristic) adds flags for detected content. |
|
||||||
|
| **Storage** | Flags are stored alongside the content record and indexed for queries. |
|
||||||
|
| **Distribution**| Flags are re-checked against the current registry before serving. |
|
||||||
|
| **Runtime** | The client enforces flags before loading content (see §4). |
|
||||||
|
|
||||||
|
### 3.3 Data Model
|
||||||
|
|
||||||
|
Flags are stored as a **normalized join table** so they can be queried and
|
||||||
|
aggregated efficiently:
|
||||||
|
|
||||||
|
```
|
||||||
|
content_item (id, type, owner_id, ...)
|
||||||
|
content_flag (content_id, flag_id, source, reason, created_at, actor_id)
|
||||||
|
flag_registry (id, category, severity, scope, mature, ...)
|
||||||
|
```
|
||||||
|
|
||||||
|
Aggregation is computed by a SQL view / query that joins a content item's
|
||||||
|
transitive dependencies. Because the graph is a DAG, this is a bounded
|
||||||
|
recursive query (PostgreSQL `WITH RECURSIVE`).
|
||||||
|
|
||||||
|
---
|
||||||
|
|
||||||
|
## 4. Enforcement
|
||||||
|
|
||||||
|
Enforcement happens at three layers, in order:
|
||||||
|
|
||||||
|
### 4.1 Load-Time Enforcement (Server)
|
||||||
|
|
||||||
|
Before a client is allowed to **request** content, the server evaluates the
|
||||||
|
content's effective flag set against the requesting account's **content
|
||||||
|
preferences** and **age verification status**:
|
||||||
|
|
||||||
|
- If the content is `mature` and the account is **not age-verified**, the
|
||||||
|
request is **rejected** with a `403 MATURE_CONTENT_REQUIRES_VERIFICATION`.
|
||||||
|
- If the content's flags exceed the account's **content filter** (a per-account
|
||||||
|
severity threshold per category), the request is rejected or the offending
|
||||||
|
content is **stripped** (e.g., audio muted, mesh hidden, script not loaded).
|
||||||
|
|
||||||
|
### 4.2 Runtime Enforcement (Client)
|
||||||
|
|
||||||
|
The client receives a **manifest** of allowed content from the server. It never
|
||||||
|
loads content that is not in the manifest. This prevents a malicious or buggy
|
||||||
|
client from bypassing the server's filter by loading content directly.
|
||||||
|
|
||||||
|
- Assets not in the manifest are **not instantiated**.
|
||||||
|
- Scripts not in the manifest are **not executed**.
|
||||||
|
- Rooms not in the manifest are **not entered**.
|
||||||
|
|
||||||
|
### 4.3 Network Boundary Enforcement
|
||||||
|
|
||||||
|
The server **filters replication** based on flags:
|
||||||
|
|
||||||
|
- Mature or filtered content is **not replicated** to clients that cannot
|
||||||
|
receive it.
|
||||||
|
- A room's flag set is broadcast in the room metadata so clients can show a
|
||||||
|
warning before entry.
|
||||||
|
|
||||||
|
### 4.4 Enforcement Decision Flow
|
||||||
|
|
||||||
|
```
|
||||||
|
Client requests content C for account A
|
||||||
|
│
|
||||||
|
▼
|
||||||
|
Compute effective flags F(C) [union + max-severity aggregation]
|
||||||
|
│
|
||||||
|
▼
|
||||||
|
Is A age-verified? ──no──► Is F(C).mature? ──yes──► REJECT (403)
|
||||||
|
│ yes │ no
|
||||||
|
▼ ▼
|
||||||
|
Does F(C) exceed A's filter? ──► yes ──► REJECT or STRIP
|
||||||
|
│ no
|
||||||
|
▼
|
||||||
|
Serve content + manifest
|
||||||
|
```
|
||||||
|
|
||||||
|
---
|
||||||
|
|
||||||
|
## 5. Age Verification Flow
|
||||||
|
|
||||||
|
Age verification is a **two-tier** system:
|
||||||
|
|
||||||
|
- **Tier 1 — Self-declaration:** The user asserts their date of birth. This is
|
||||||
|
fast, requires no PII beyond a birthdate, and is sufficient for most content.
|
||||||
|
- **Tier 2 — ID check (optional hook):** A pluggable identity-verification
|
||||||
|
provider confirms the user is an adult. This raises the account's assurance
|
||||||
|
level and unlocks the highest maturity tier.
|
||||||
|
|
||||||
|
### 5.1 Verification States
|
||||||
|
|
||||||
|
An account has an **age verification status**:
|
||||||
|
|
||||||
|
| Status | Meaning |
|
||||||
|
|-------------------|----------------------------------------------------------------------|
|
||||||
|
| `unverified` | No declaration on file. |
|
||||||
|
| `self_declared` | User declared a birthdate; **not** independently confirmed. |
|
||||||
|
| `id_verified` | User passed the ID check hook; independently confirmed adult. |
|
||||||
|
| `rejected` | ID check failed or declaration was inconsistent. |
|
||||||
|
|
||||||
|
### 5.2 Tier 1 — Self-Declaration Flow
|
||||||
|
|
||||||
|
```
|
||||||
|
User submits { date_of_birth }
|
||||||
|
│
|
||||||
|
▼
|
||||||
|
Server validates format & plausibility (age 13–120, not in future)
|
||||||
|
│
|
||||||
|
▼
|
||||||
|
Compute age from DOB
|
||||||
|
│
|
||||||
|
▼
|
||||||
|
age >= 18 ──► status = self_declared (adult)
|
||||||
|
age >= 13 ──► status = self_declared (minor, restricted)
|
||||||
|
age < 13 ──► status = rejected (below minimum platform age)
|
||||||
|
```
|
||||||
|
|
||||||
|
- The DOB is stored **encrypted at rest** and is **never exposed** to other
|
||||||
|
players.
|
||||||
|
- A user may **upgrade** from `self_declared` to `id_verified` at any time via
|
||||||
|
Tier 2.
|
||||||
|
|
||||||
|
### 5.3 Tier 2 — ID Check Hook
|
||||||
|
|
||||||
|
The ID check is an **optional, pluggable hook**. The platform defines an
|
||||||
|
interface; concrete providers (e.g., a third-party KYC service) implement it.
|
||||||
|
|
||||||
|
```
|
||||||
|
User requests ID verification
|
||||||
|
│
|
||||||
|
▼
|
||||||
|
Server creates a verification session (idempotent, expiring)
|
||||||
|
│
|
||||||
|
▼
|
||||||
|
Server calls provider hook: verify(identity_token) -> { adult: bool, ref: string }
|
||||||
|
│
|
||||||
|
▼
|
||||||
|
adult == true ──► status = id_verified, store provider ref (not raw doc)
|
||||||
|
adult == false ─► status = rejected
|
||||||
|
provider error ──► status unchanged, retry allowed
|
||||||
|
```
|
||||||
|
|
||||||
|
**Privacy guarantees:**
|
||||||
|
|
||||||
|
- The platform **never stores** the raw identity document or image.
|
||||||
|
- Only the provider's **opaque reference** and the boolean `adult` result are
|
||||||
|
persisted.
|
||||||
|
- The hook is **asynchronous and idempotent**; a session can be retried without
|
||||||
|
double-charging or double-verifying.
|
||||||
|
|
||||||
|
### 5.4 Hook Interface
|
||||||
|
|
||||||
|
The ID check hook is defined as a backend interface (FastAPI dependency /
|
||||||
|
abstract service):
|
||||||
|
|
||||||
|
```python
|
||||||
|
class IdentityVerificationProvider(Protocol):
|
||||||
|
def create_session(self, user_id: str) -> VerificationSession: ...
|
||||||
|
def verify(self, session_id: str, identity_token: str) -> VerificationResult: ...
|
||||||
|
|
||||||
|
class VerificationResult:
|
||||||
|
adult: bool
|
||||||
|
provider_ref: str | None
|
||||||
|
error: str | None
|
||||||
|
```
|
||||||
|
|
||||||
|
A default **no-op provider** returns `adult=False` with a clear error, so the
|
||||||
|
system runs without any third-party integration until one is configured.
|
||||||
|
|
||||||
|
### 5.5 Age Gate Enforcement
|
||||||
|
|
||||||
|
The age gate is enforced at **load time** (see §4.1):
|
||||||
|
|
||||||
|
| Verification status | Can access `mature` content? |
|
||||||
|
|---------------------|------------------------------|
|
||||||
|
| `unverified` | No |
|
||||||
|
| `self_declared` | Yes (adult) / No (minor) |
|
||||||
|
| `id_verified` | Yes |
|
||||||
|
| `rejected` | No |
|
||||||
|
|
||||||
|
---
|
||||||
|
|
||||||
|
## 6. Moderation Workflow
|
||||||
|
|
||||||
|
### 6.1 Flagging Sources
|
||||||
|
|
||||||
|
Content can be flagged by:
|
||||||
|
|
||||||
|
- **Author** (self-declared at upload).
|
||||||
|
- **Automated scanner** (hash-based detection, heuristic analysis).
|
||||||
|
- **Community** (players report content; reports become flags after review).
|
||||||
|
- **Moderator** (manual review and override).
|
||||||
|
|
||||||
|
### 6.2 Review Queue
|
||||||
|
|
||||||
|
Community and automated flags enter a **review queue**. A moderator either:
|
||||||
|
|
||||||
|
- **Approves** the flag (it becomes authoritative), or
|
||||||
|
- **Rejects** the flag (it is discarded), or
|
||||||
|
- **Escalates** to a senior moderator for severe/hate flags.
|
||||||
|
|
||||||
|
### 6.3 Actions
|
||||||
|
|
||||||
|
Once a flag is authoritative, a moderator can take actions:
|
||||||
|
|
||||||
|
| Action | Effect |
|
||||||
|
|-----------------|---------------------------------------------------------------|
|
||||||
|
| `warn` | Notify the author; content remains. |
|
||||||
|
| `restrict` | Content hidden from users below a filter threshold. |
|
||||||
|
| `age_gate` | Content marked `mature`; requires age verification. |
|
||||||
|
| `remove` | Content taken down; not served. |
|
||||||
|
| `ban_author` | Author's upload privileges suspended. |
|
||||||
|
|
||||||
|
### 6.4 Audit Log
|
||||||
|
|
||||||
|
Every flag and action is written to an **audit log**:
|
||||||
|
|
||||||
|
```
|
||||||
|
audit_event (id, content_id, actor_id, action, flag_id, reason, created_at)
|
||||||
|
```
|
||||||
|
|
||||||
|
This log is append-only and used for transparency and dispute resolution.
|
||||||
|
|
||||||
|
---
|
||||||
|
|
||||||
|
## 7. Client-Side Integration (Godot)
|
||||||
|
|
||||||
|
### 7.1 Content Manifest
|
||||||
|
|
||||||
|
The server sends each client a **content manifest** — the set of content the
|
||||||
|
client is permitted to load, derived from the account's verification status and
|
||||||
|
filter. The Godot client:
|
||||||
|
|
||||||
|
- Loads only manifest-listed assets.
|
||||||
|
- Executes only manifest-listed scripts.
|
||||||
|
- Shows a **maturity warning** dialog before entering a room whose effective
|
||||||
|
flags include `mature` content.
|
||||||
|
|
||||||
|
### 7.2 Flag Metadata on Content
|
||||||
|
|
||||||
|
Each content resource carries a `content_flags` metadata field (a Godot
|
||||||
|
`Dictionary` or custom `Resource`). The client uses this for local UI decisions
|
||||||
|
(e.g., showing a warning icon) but **never** as the authority for whether to
|
||||||
|
load — the server manifest is authoritative.
|
||||||
|
|
||||||
|
### 7.3 Age Verification UI
|
||||||
|
|
||||||
|
The client exposes an **age verification screen**:
|
||||||
|
|
||||||
|
- Tier 1: a date-of-birth picker.
|
||||||
|
- Tier 2: a button that opens the ID check provider flow (deep link / webview).
|
||||||
|
|
||||||
|
The client calls the backend endpoints (§8) and reflects the resulting status.
|
||||||
|
|
||||||
|
---
|
||||||
|
|
||||||
|
## 8. Backend API Surface
|
||||||
|
|
||||||
|
| Method | Path | Description |
|
||||||
|
|--------|-----------------------------------|------------------------------------------------|
|
||||||
|
| `POST` | `/v1/age/declare` | Submit self-declared DOB (Tier 1). |
|
||||||
|
| `POST` | `/v1/age/verify/session` | Create an ID-check session (Tier 2). |
|
||||||
|
| `POST` | `/v1/age/verify/confirm` | Confirm an ID-check session with a token. |
|
||||||
|
| `GET` | `/v1/age/status` | Return the account's verification status. |
|
||||||
|
| `GET` | `/v1/content/{id}/flags` | Return a content item's effective flags. |
|
||||||
|
| `POST` | `/v1/content/{id}/flags` | Add a flag (author/community). |
|
||||||
|
| `POST` | `/v1/moderation/review/{flag_id}` | Moderator approve/reject/escalate. |
|
||||||
|
| `POST` | `/v1/moderation/action` | Apply a moderation action. |
|
||||||
|
| `GET` | `/v1/manifest` | Return the client's permitted content manifest.|
|
||||||
|
|
||||||
|
All endpoints require a valid **JWT** (matching the existing auth stack). The
|
||||||
|
age endpoints additionally require the account to be in a non-`rejected` state.
|
||||||
|
|
||||||
|
---
|
||||||
|
|
||||||
|
## 9. Security & Privacy Considerations
|
||||||
|
|
||||||
|
- **DOB encryption:** Self-declared birthdates are encrypted at rest; only the
|
||||||
|
derived age and verification status are used in authorization decisions.
|
||||||
|
- **No raw identity storage:** The ID check hook persists only a provider
|
||||||
|
reference and a boolean result.
|
||||||
|
- **Server authority:** The client manifest prevents bypass; the client never
|
||||||
|
trusts its own flag metadata for access decisions.
|
||||||
|
- **Rate limiting:** Age-declaration and ID-check endpoints are rate-limited to
|
||||||
|
prevent abuse and enumeration.
|
||||||
|
- **Auditability:** All flag and verification events are logged append-only.
|
||||||
|
|
||||||
|
---
|
||||||
|
|
||||||
|
## 10. Open Questions / Future Work
|
||||||
|
|
||||||
|
- **Regional age thresholds:** Different jurisdictions may require different
|
||||||
|
minimum ages; the threshold should be configurable per region.
|
||||||
|
- **Parental controls:** A future feature may let a parent set a content filter
|
||||||
|
on a minor's account.
|
||||||
|
- **Automated scanner accuracy:** The heuristic scanner may produce false
|
||||||
|
positives; a confidence score should be attached to automated flags.
|
||||||
|
- **Offline / local content:** How flags apply to locally-authored content that
|
||||||
|
is never uploaded remains to be defined.
|
||||||
@@ -0,0 +1,286 @@
|
|||||||
|
# Multiplayer Networking Architecture
|
||||||
|
|
||||||
|
> **Status:** Proposed
|
||||||
|
> **Owner:** Platform team
|
||||||
|
> **Related:** Server authority + client prediction
|
||||||
|
|
||||||
|
## 1. Overview
|
||||||
|
|
||||||
|
This document specifies the multiplayer networking architecture for **agp-game**,
|
||||||
|
a Godot-based game built by autonomous agents. The architecture follows a
|
||||||
|
**server-authoritative model with client-side prediction and reconciliation**,
|
||||||
|
which is the industry standard for fast-paced, competitive multiplayer games.
|
||||||
|
|
||||||
|
The goals of this architecture are:
|
||||||
|
|
||||||
|
- **Fairness & anti-cheat:** The server is the single source of truth for all
|
||||||
|
gameplay state. Clients never directly mutate world state.
|
||||||
|
- **Responsiveness:** Client-side prediction hides network latency so local input
|
||||||
|
feels immediate.
|
||||||
|
- **Determinism:** The server runs a fixed-timestep simulation so that state is
|
||||||
|
reproducible and testable.
|
||||||
|
- **Scalability:** A clear separation between transport, simulation, and
|
||||||
|
replication layers allows the server to be tuned independently.
|
||||||
|
|
||||||
|
---
|
||||||
|
|
||||||
|
## 2. Transport Choice: ENet over WebSocket
|
||||||
|
|
||||||
|
### 2.1 Decision
|
||||||
|
|
||||||
|
We choose **ENet** as the primary transport for gameplay traffic.
|
||||||
|
|
||||||
|
### 2.2 Justification
|
||||||
|
|
||||||
|
| Criterion | ENet | WebSocket (TCP) |
|
||||||
|
|----------------------|----------------------------------------|-------------------------------------|
|
||||||
|
| **Reliability model**| Reliable + unreliable channels | Reliable only (TCP) |
|
||||||
|
| **Latency** | Low; unreliable packets skip retransmit| Head-of-line blocking on loss |
|
||||||
|
| **Packet ordering** | Per-channel ordering | Global strict ordering |
|
||||||
|
| **Congestion control**| Lightweight, game-oriented | TCP-style (slow start, backoff) |
|
||||||
|
| **Godot support** | First-class (`ENetConnection`, `MultiplayerPeerENet`) | Supported but TCP-based |
|
||||||
|
| **Use case fit** | Real-time action game | Chat, lobby, HTTP-style messaging |
|
||||||
|
|
||||||
|
**Rationale:**
|
||||||
|
|
||||||
|
- **Movement & state replication** are latency-sensitive and tolerate occasional
|
||||||
|
packet loss. ENet's *unreliable* channel lets us send position snapshots at high
|
||||||
|
frequency without head-of-line blocking.
|
||||||
|
- **RPCs that must be delivered** (e.g., interactions, spawns) use ENet's
|
||||||
|
*reliable* channel, giving us exactly the semantics we need without TCP's
|
||||||
|
retransmission stalls.
|
||||||
|
- Godot's `MultiplayerPeerENet` is mature and integrates directly with the
|
||||||
|
high-level multiplayer API (`MultiplayerAPI`, `rpc()`).
|
||||||
|
|
||||||
|
### 2.3 WebSocket as a Secondary Transport
|
||||||
|
|
||||||
|
WebSocket remains available as a **secondary transport** for:
|
||||||
|
|
||||||
|
- **Lobby / matchmaking** messaging (low-frequency, must-be-reliable).
|
||||||
|
- **Browser builds** where raw UDP/ENet is unavailable.
|
||||||
|
- **Admin / telemetry** channels.
|
||||||
|
|
||||||
|
The transport layer is abstracted behind an interface so gameplay code does not
|
||||||
|
depend on the underlying protocol.
|
||||||
|
|
||||||
|
---
|
||||||
|
|
||||||
|
## 3. Server-Side Game Loop
|
||||||
|
|
||||||
|
### 3.1 Tick Rate
|
||||||
|
|
||||||
|
- **Simulation tick rate:** **30 Hz** (33.33 ms per tick).
|
||||||
|
- **Replication / snapshot rate:** **30 Hz**, aligned with the simulation tick.
|
||||||
|
|
||||||
|
**Justification:**
|
||||||
|
|
||||||
|
- 30 Hz is sufficient for smooth movement and interaction in a top-down / 2D
|
||||||
|
action game while keeping CPU and bandwidth costs predictable.
|
||||||
|
- A fixed timestep (rather than delta-time) makes the simulation deterministic
|
||||||
|
and testable.
|
||||||
|
- The tick rate is a **configuration constant** so it can be raised (e.g., to
|
||||||
|
60 Hz) for competitive modes without architectural changes.
|
||||||
|
|
||||||
|
### 3.2 Authority Model
|
||||||
|
|
||||||
|
- **Server is authoritative** for:
|
||||||
|
- Player position, velocity, and physics state.
|
||||||
|
- Health, damage, and death.
|
||||||
|
- Item pickups, inventory, and world-object state.
|
||||||
|
- Spawning and despawning of entities.
|
||||||
|
- Game rules, scoring, and win/lose conditions.
|
||||||
|
- **Client is authoritative** for:
|
||||||
|
- Its own *input* (which keys/buttons are pressed).
|
||||||
|
- Local camera and UI.
|
||||||
|
- Cosmetic / non-gameplay presentation.
|
||||||
|
|
||||||
|
### 3.3 Server Loop Pseudocode
|
||||||
|
|
||||||
|
```
|
||||||
|
while server_running:
|
||||||
|
process_network_inbound() # read client inputs & RPCs
|
||||||
|
for _ in range(ticks_to_advance):
|
||||||
|
simulate_tick() # fixed 30 Hz step
|
||||||
|
broadcast_snapshots() # replicate authoritative state
|
||||||
|
process_network_outbound() # flush reliable/unreliable channels
|
||||||
|
```
|
||||||
|
|
||||||
|
The server accumulates real elapsed time and advances the simulation in fixed
|
||||||
|
`TICK_DURATION` increments, decoupling simulation from frame rate.
|
||||||
|
|
||||||
|
---
|
||||||
|
|
||||||
|
## 4. RPC Call Patterns
|
||||||
|
|
||||||
|
RPCs are grouped by direction and reliability. All gameplay RPCs are routed
|
||||||
|
through the high-level `MultiplayerAPI` with explicit `rpc_id` targeting.
|
||||||
|
|
||||||
|
### 4.1 Client → Server (Input & Requests)
|
||||||
|
|
||||||
|
| RPC | Channel | Payload | Notes |
|
||||||
|
|------------------------------|-----------|-------------------------------------------|-------|
|
||||||
|
| `request_move_input` | unreliable| `{ seq, input_state, timestamp }` | Batched per tick; drives prediction |
|
||||||
|
| `request_interact` | reliable | `{ target_id }` | Open door, pick up item, use object |
|
||||||
|
| `request_attack` | reliable | `{ target_id, aim_dir }` | Combat action |
|
||||||
|
| `request_join` | reliable | `{ player_name, profile }` | Session setup |
|
||||||
|
| `request_respawn` | reliable | `{}` | After death |
|
||||||
|
|
||||||
|
**Design notes:**
|
||||||
|
|
||||||
|
- **Input is batched** per client tick and sent with a monotonically increasing
|
||||||
|
`seq` so the server can detect gaps and the client can reconcile.
|
||||||
|
- **Interactions are reliable** because they are discrete, must-happen events
|
||||||
|
(opening a door, picking up an item). Losing them would corrupt world state.
|
||||||
|
|
||||||
|
### 4.2 Server → Client (State & Events)
|
||||||
|
|
||||||
|
| RPC | Channel | Payload | Notes |
|
||||||
|
|------------------------------|-----------|-------------------------------------------|-------|
|
||||||
|
| `snapshot_state` | unreliable| `{ tick, entities[], player_states[] }` | Periodic authoritative state |
|
||||||
|
| `spawn_entity` | reliable | `{ entity_id, type, transform, props }` | New entity enters world |
|
||||||
|
| `despawn_entity` | reliable | `{ entity_id, reason }` | Entity removed |
|
||||||
|
| `interact_result` | reliable | `{ request_seq, success, result }` | Acknowledges interaction |
|
||||||
|
| `damage_event` | reliable | `{ target_id, amount, source_id }` | Combat feedback |
|
||||||
|
| `game_event` | reliable | `{ type, payload }` | Score, win, round start/end |
|
||||||
|
|
||||||
|
### 4.3 Broadcast vs. Targeted
|
||||||
|
|
||||||
|
- **Broadcast (all clients):** `snapshot_state`, `spawn_entity`,
|
||||||
|
`despawn_entity`, `game_event`.
|
||||||
|
- **Targeted (single client):** `interact_result`, `damage_event` (to affected
|
||||||
|
players), and any player-private data.
|
||||||
|
|
||||||
|
---
|
||||||
|
|
||||||
|
## 5. Client-Side Prediction & Reconciliation
|
||||||
|
|
||||||
|
### 5.1 Prediction
|
||||||
|
|
||||||
|
- The client runs a **local copy of the movement simulation** using the same
|
||||||
|
physics constants as the server.
|
||||||
|
- When the player provides input, the client:
|
||||||
|
1. Applies the input to its local player immediately.
|
||||||
|
2. Renders the predicted position.
|
||||||
|
3. Sends the input to the server (batched, with `seq`).
|
||||||
|
|
||||||
|
### 5.2 Reconciliation
|
||||||
|
|
||||||
|
- The server sends authoritative `snapshot_state` at 30 Hz containing the
|
||||||
|
server's tick number and authoritative player positions.
|
||||||
|
- The client keeps a **ring buffer of predicted states** keyed by input `seq`.
|
||||||
|
- On receiving a snapshot:
|
||||||
|
1. Find the last predicted state that matches the server's tick.
|
||||||
|
2. Compute the **error** between predicted and authoritative position.
|
||||||
|
3. If error exceeds a threshold, **snap or smoothly interpolate** the local
|
||||||
|
player to the authoritative position (error correction).
|
||||||
|
4. Re-simulate any inputs that occurred after the server's tick (rollback).
|
||||||
|
|
||||||
|
### 5.3 Interpolation of Remote Entities
|
||||||
|
|
||||||
|
- **Local player:** predicted + reconciled (see above).
|
||||||
|
- **Remote players / entities:** rendered with **interpolation delay** of
|
||||||
|
`2 × TICK_DURATION` (≈ 66 ms) to smooth out snapshot jitter.
|
||||||
|
- The client buffers the last N snapshots and interpolates between them.
|
||||||
|
|
||||||
|
### 5.4 Prediction Buffer Sizing
|
||||||
|
|
||||||
|
- Buffer size is adaptive based on measured RTT.
|
||||||
|
- Default: hold up to `ceil(RTT / TICK_DURATION) + 2` predicted states.
|
||||||
|
|
||||||
|
---
|
||||||
|
|
||||||
|
## 6. Entity & World State Replication
|
||||||
|
|
||||||
|
### 6.1 Entity Model
|
||||||
|
|
||||||
|
Every networked entity has:
|
||||||
|
|
||||||
|
- A globally unique `entity_id` (server-assigned).
|
||||||
|
- An `EntityType` (player, enemy, item, projectile, door, ...).
|
||||||
|
- A `Transform` (position, rotation).
|
||||||
|
- A typed `props` dictionary of gameplay state (health, state machine, etc.).
|
||||||
|
|
||||||
|
### 6.2 Snapshot Format
|
||||||
|
|
||||||
|
```
|
||||||
|
snapshot_state:
|
||||||
|
tick: uint32
|
||||||
|
entities:
|
||||||
|
- entity_id: uint32
|
||||||
|
type: uint8
|
||||||
|
transform: { x, y, rot }
|
||||||
|
props: { ... } # delta-encoded where possible
|
||||||
|
player_states:
|
||||||
|
- peer_id: int
|
||||||
|
entity_id: uint32
|
||||||
|
health: int
|
||||||
|
state: uint8
|
||||||
|
```
|
||||||
|
|
||||||
|
### 6.3 Delta Compression
|
||||||
|
|
||||||
|
- Only **changed** entity fields are sent per snapshot (dirty-flag per entity).
|
||||||
|
- Static or unchanged entities are omitted from the snapshot.
|
||||||
|
- This keeps bandwidth proportional to *activity*, not world size.
|
||||||
|
|
||||||
|
---
|
||||||
|
|
||||||
|
## 7. Connection & Session Lifecycle
|
||||||
|
|
||||||
|
1. **Connect:** Client opens an ENet connection to the server.
|
||||||
|
2. **Authenticate / Join:** Client sends `request_join`; server validates and
|
||||||
|
assigns a `peer_id` and spawns the player entity.
|
||||||
|
3. **Spawn:** Server broadcasts `spawn_entity` for the new player to all clients.
|
||||||
|
4. **Play:** Input → prediction → server simulation → snapshot → reconciliation.
|
||||||
|
5. **Disconnect:** Server removes the player entity, broadcasts `despawn_entity`,
|
||||||
|
and cleans up session state.
|
||||||
|
|
||||||
|
---
|
||||||
|
|
||||||
|
## 8. Security & Anti-Cheat
|
||||||
|
|
||||||
|
- **No client-authoritative gameplay values.** Clients only send *inputs* and
|
||||||
|
*requests*; the server computes all outcomes.
|
||||||
|
- **Input validation:** Server clamps movement speed, rejects out-of-bounds
|
||||||
|
positions, and validates interaction targets.
|
||||||
|
- **Rate limiting:** Per-peer input and RPC rate limits prevent flooding.
|
||||||
|
- **Sequence validation:** Gaps or replays in input `seq` are detected and
|
||||||
|
rejected.
|
||||||
|
|
||||||
|
---
|
||||||
|
|
||||||
|
## 9. Testing & Determinism
|
||||||
|
|
||||||
|
- The simulation is a **pure function of (state, inputs, tick)** so it can be
|
||||||
|
unit-tested headlessly.
|
||||||
|
- A **replay system** records inputs and can re-simulate to verify server and
|
||||||
|
client produce identical results.
|
||||||
|
- Network code is tested with a **mock transport** that can inject latency,
|
||||||
|
jitter, and packet loss.
|
||||||
|
|
||||||
|
---
|
||||||
|
|
||||||
|
## 10. Open Questions / Future Work
|
||||||
|
|
||||||
|
- **Interest management / spatial partitioning:** For large worlds, restrict
|
||||||
|
snapshots to entities near each client (AOI culling).
|
||||||
|
- **Server-side physics:** Decide whether to use Godot's physics server on the
|
||||||
|
host or a custom deterministic physics step.
|
||||||
|
- **Dedicated server vs. listen server:** The architecture supports both; a
|
||||||
|
dedicated headless server is the target for production.
|
||||||
|
- **WebSocket fallback:** Implement the transport abstraction for browser builds.
|
||||||
|
|
||||||
|
---
|
||||||
|
|
||||||
|
## 11. Summary
|
||||||
|
|
||||||
|
| Concern | Decision |
|
||||||
|
|------------------------|-------------------------------------------------|
|
||||||
|
| Transport | ENet (primary), WebSocket (secondary) |
|
||||||
|
| Tick rate | 30 Hz fixed timestep |
|
||||||
|
| Authority | Server-authoritative; client sends input only |
|
||||||
|
| Prediction | Client-side prediction + reconciliation |
|
||||||
|
| Remote interpolation | 2-tick interpolation delay |
|
||||||
|
| Replication | Delta-compressed snapshots at 30 Hz |
|
||||||
|
| Interaction RPCs | Reliable channel |
|
||||||
|
| Movement input | Unreliable channel, batched with sequence |
|
||||||
@@ -0,0 +1 @@
|
|||||||
|
testing coder-bot identity
|
||||||
Reference in New Issue
Block a user