# BlenderMCP for 3D Avatar Creation via Kasm Workstation * Status: proposed * Date: 2026-02-21 * Deciders: Billy * Technical Story: Enable AI-assisted 3D avatar creation for companions-frontend using BlenderMCP in a Kasm Blender workstation with VS Code, storing assets in S3, serving locally from gravenhollow NFS and remotely via Cloudflare R2 CDN ## Context and Problem Statement The companions-frontend serves VRM avatar models for its Three.js-based 3D character rendering (see [ADR-0046](0046-companions-frontend-architecture.md)). Today the avatar library is limited to three models (`Seed-san.vrm`, `Aka.vrm`, `Midori.vrm`) — only one of which actually ships in the repo — and every model must be sourced or hand-sculpted externally. Creating custom VRM avatars is a manual, time-intensive process: open Blender, sculpt/rig a character, export to VRM, iterate. There is no integration between the AI coding workflow (VS Code / Copilot) and Blender, so context switching between the editor and the 3D tool is constant. How do we streamline custom 3D avatar creation for companions-frontend with AI assistance, while keeping assets durable and accessible across workstations? ## Decision Drivers * The existing avatar pipeline is manual and disconnected from the development workflow * BlenderMCP (v1.5.5, 17k+ GitHub stars) bridges AI assistants to Blender via the Model Context Protocol — enabling prompt-driven 3D modelling, material control, scene manipulation, and code execution inside Blender * Kasm Workspaces already run in the cluster (`productivity` namespace) and support Docker-in-Docker with volume plugins for persistent storage * VS Code supports MCP servers natively (GitHub Copilot agent mode), meaning the same editor used for code can drive Blender scene creation * Custom volume mounts in Kasm map `/s3` to S3-compatible storage via the rclone Docker volume plugin — providing durable, off-node persistence * Quobyte S3-compatible endpoint with the `kasm` bucket is the existing Kasm storage backend * VRM models must ultimately land in the companions-frontend `/assets/models/` path at build time or be served from an external URL * Final production models and animations should live on gravenhollow (all-SSD TrueNAS, dual 10GbE) for fast local serving via NFS * Remote users accessing companions-chat through Cloudflare Tunnel need a CDN-backed path for multi-MB VRM downloads * Models are write-once/read-many — ideal for aggressive caching ## Considered Options 1. **BlenderMCP in Kasm Blender workstation + VS Code MCP client, assets in Quobyte S3 (`kasm` bucket)** 2. **Local Blender + BlenderMCP on a developer laptop** 3. **Hyper3D / Rodin cloud generation only (no Blender)** 4. **Manual Blender workflow (status quo)** ## Decision Outcome Chosen option: **Option 1 — BlenderMCP in Kasm Blender workstation + VS Code MCP client, assets in Quobyte S3**, because it integrates AI-assisted modelling directly into the existing Kasm + VS Code workflow, stores assets durably in S3, and requires no additional infrastructure beyond what is already deployed. ### Positive Consequences * AI-assisted 3D modelling — prompt-driven creation, material application, and scene manipulation inside Blender via MCP * Zero context switching — VS Code agent mode drives Blender commands through the same editor used for code * Persistent storage — VRM exports written to `/s3` survive session teardown and are available from any Kasm session or CI pipeline * Existing infrastructure — Kasm agent, DinD, rclone volume plugin, Quobyte S3, gravenhollow NFS, and Cloudflare are all already deployed * No image rebuild for new models — VRM files live on gravenhollow NFS, mounted read-only into the pod; add a model and update the allowlist * LAN performance — all-SSD NFS with dual 10GbE delivers VRM files in <100ms * Remote performance — Cloudflare R2 CDN with zero egress fees and 300+ global PoPs for remote users via Cloudflare Tunnel * Poly Haven / Hyper3D integration — BlenderMCP supports downloading Poly Haven assets and generating models via Hyper3D Rodin, expanding the asset library * VRM ecosystem — Blender VRM add-on exports directly to VRM 0.x/1.0 format consumed by `@pixiv/three-vrm` in companions-frontend * Reproducible — Kasm workspace images are versioned; Blender + add-ons are pre-baked ### Negative Consequences * BlenderMCP `execute_blender_code` tool runs arbitrary Python in Blender — must trust AI-generated code or review before execution * Socket-based communication (TCP 9876) between the MCP server and Blender add-on adds a failure mode * VRM export quality depends on correct rigging/weight painting — AI can scaffold but manual touch-up may still be needed * Kasm Blender image must be configured with both the BlenderMCP add-on and the VRM add-on pre-installed * Telemetry is on by default in BlenderMCP — must disable via `DISABLE_TELEMETRY=true` for privacy * Cloudflare R2 sync adds a CronJob and requires a Cloudflare R2 API token in Vault * Two-hop promotion path (Quobyte S3 → gravenhollow NFS → Cloudflare R2) adds operational steps ## Architecture ``` ┌─────────────────────────────────────────────────────────────────────────┐ │ Developer Workstation │ │ │ │ ┌──────────────────────────────────┐ │ │ │ VS Code (local) │ │ │ │ │ │ │ │ GitHub Copilot (agent mode) │ │ │ │ │ │ │ │ │ ▼ │ │ │ │ BlenderMCP Server (MCP) │ │ │ │ (uvx blender-mcp) │ │ │ │ │ │ │ │ └─────────┼────────────────────────┘ │ │ │ TCP :9876 (JSON over socket) │ └────────────┼────────────────────────────────────────────────────────────┘ │ ▼ ┌─────────────────────────────────────────────────────────────────────────┐ │ Kasm Blender Workstation (browser session) │ │ kasm.daviestechlabs.io │ │ │ │ ┌──────────────────────────────────────────────────────┐ │ │ │ Blender 4.x │ │ │ │ │ │ │ │ Add-ons: │ │ │ │ • BlenderMCP (addon.py) — socket server :9876 │ │ │ │ • VRM Add-on for Blender — import/export VRM │ │ │ │ │ │ │ │ ┌────────────────────────────────────────────────┐ │ │ │ │ │ /s3/blender-avatars/ │ │ │ │ │ │ ├── projects/ (.blend source files) │ │ │ │ │ │ ├── exports/ (.vrm exported models) │ │ │ │ │ │ └── textures/ (shared texture lib) │ │ │ │ │ └────────────────────────────────────────────────┘ │ │ │ └──────────────────────────────────────────────────────┘ │ │ │ │ │ rclone volume │ │ plugin (S3) │ └──────────────────────────┼──────────────────────────────────────────────┘ │ ▼ ┌─────────────────────────────────────────────────────────────────────────┐ │ Quobyte S3 Endpoint │ │ Bucket: kasm │ │ │ │ kasm/blender-avatars/projects/Companion-A.blend │ │ kasm/blender-avatars/exports/Companion-A.vrm │ │ kasm/blender-avatars/textures/skin-tone-01.png │ └──────────────────────────┬──────────────────────────────────────────────┘ │ rclone sync (promotion) │ ▼ ┌─────────────────────────────────────────────────────────────────────────┐ │ gravenhollow.lab.daviestechlabs.io │ │ (TrueNAS Scale · All-SSD · Dual 10GbE · 12.2 TB) │ │ │ │ NFS: /mnt/gravenhollow/kubernetes/avatar-models/ │ │ ├── Seed-san.vrm (default model) │ │ ├── Aka.vrm (Legend tier) │ │ ├── Midori.vrm (Legend tier) │ │ ├── Companion-A.vrm (custom, promoted from Kasm S3) │ │ └── animations/ (shared animation clips) │ │ │ │ S3 (RustFS): avatar-models bucket │ │ (mirror of NFS dir for Cloudflare R2 sync) │ └──────────┬─────────────────────────────────┬────────────────────────────┘ │ │ NFS mount (nfs-fast) rclone sync (cron) │ │ ▼ ▼ ┌──────────────────────────┐ ┌──────────────────────────────────────────┐ │ companions-frontend │ │ Cloudflare R2 │ │ (Kubernetes pod) │ │ Bucket: avatar-models │ │ │ │ │ │ /models/ volume mount │ │ Custom domain: │ │ (nfs-fast PVC, RO) │ │ assets.daviestechlabs.io/models/ │ │ │ │ │ │ Go FileServer: │ │ Cache-Control: public, max-age=31536000 │ │ /assets/models/ → │ │ (immutable, versioned filenames) │ │ serves from PVC │ │ │ │ │ │ Free egress (no bandwidth charges) │ └──────────┬───────────────┘ └──────────────────────┬───────────────────┘ │ │ LAN clients Remote clients companions-chat.lab... companions-chat via (envoy-internal, direct) Cloudflare Tunnel │ │ └──────────────────┬───────────────────────┘ ▼ ┌─────────────────────────────────────────────────────────────────────────┐ │ Browser (Three.js) │ │ AvatarManager.loadModel('/assets/models/Companion-A.vrm') │ │ │ │ LAN: fetch from companions-frontend pod (NFS-backed, ~10GbE) │ │ Remote: fetch from Cloudflare R2 CDN (cache-hit, global PoPs) │ └─────────────────────────────────────────────────────────────────────────┘ ``` ## Workflow ### 1. Kasm Workspace Setup The Kasm Blender workspace image is configured with: | Component | Version | Purpose | |-----------|---------|---------| | Blender | 4.x | 3D modelling and sculpting | | BlenderMCP add-on (`addon.py`) | 1.5.5 | Socket server for MCP commands | | VRM Add-on for Blender | latest | Import/export VRM format | | Python | 3.10+ | Blender scripting runtime | The Kasm storage mapping mounts `/s3` via the rclone Docker volume plugin to the Quobyte S3 endpoint (`kasm` bucket). The sub-path `blender-avatars/` is used for all 3D asset work. ### 2. VS Code MCP Configuration Add BlenderMCP as an MCP server in VS Code (`.vscode/mcp.json` or user settings): ```json { "servers": { "blender": { "command": "uvx", "args": ["blender-mcp"], "env": { "BLENDER_HOST": "localhost", "BLENDER_PORT": "9876", "DISABLE_TELEMETRY": "true" } } } } ``` When the Kasm session is accessed remotely, set `BLENDER_HOST` to the Kasm workstation's reachable address. ### 3. Avatar Creation Workflow 1. **Launch** the Kasm Blender workspace via `kasm.daviestechlabs.io` 2. **Enable** the BlenderMCP add-on in Blender → 3D View sidebar → "BlenderMCP" tab → "Connect to Claude" 3. **Open VS Code** with Copilot agent mode and the BlenderMCP MCP server running 4. **Prompt** the AI to create or modify avatars: - _"Create a humanoid character with anime-style proportions, blue hair, and a fantasy outfit"_ - _"Apply a metallic gold material to the armor pieces"_ - _"Set up the lighting for a character showcase render"_ - _"Rig this character for VRM export with standard humanoid bones"_ 5. **Export** the finished model to VRM via the VRM add-on (or via BlenderMCP `execute_blender_code` calling the VRM export operator) 6. **Save** the `.vrm` to `/s3/blender-avatars/exports/` and the `.blend` source to `/s3/blender-avatars/projects/` 7. **Import** the VRM into companions-frontend — copy to `assets/models/`, update the allowlists in `internal/database/database.go` and `static/js/avatar.js` ### 4. Asset Pipeline (Kasm S3 → gravenhollow → production) | Stage | Action | |-------|--------| | **Create** | AI-assisted modelling + VRM export in Kasm Blender → `/s3/blender-avatars/exports/*.vrm` | | **Store** | rclone syncs `/s3` to Quobyte S3 `kasm` bucket automatically | | **Promote** | `rclone copy quobyte:kasm/blender-avatars/exports/Model.vrm gravenhollow-nfs:/avatar-models/` (manual or CI) | | **Register** | Add model path to `AllowedAvatarModels` in Go and JS allowlists, commit to repo | | **Deploy** | Flux rolls out updated companions-frontend config; model already available on NFS PVC — no image rebuild needed | | **CDN sync** | CronJob `rclone sync` from gravenhollow RustFS `avatar-models` bucket → Cloudflare R2 `avatar-models` bucket | ### 5. Deployment and Storage Architecture #### Local Serving (LAN users) Companions-frontend currently serves VRM models via `http.FileServer(http.Dir("assets"))` from the container filesystem. This bakes models into the image and requires a rebuild to add new avatars. The new approach mounts avatar models from gravenhollow via an `nfs-fast` PVC: ```yaml # PersistentVolumeClaim for avatar models apiVersion: v1 kind: PersistentVolumeClaim metadata: name: avatar-models namespace: ai-ml spec: storageClassName: nfs-fast accessModes: [ReadOnlyMany] resources: requests: storage: 10Gi ``` The pod mounts this PVC at `/models` and the Go server serves it at `/assets/models/`: ```go // Replace embedded assets with NFS-backed volume mux.Handle("/assets/models/", http.StripPrefix("/assets/models/", http.FileServer(http.Dir("/models")))) ``` Benefits: - **No image rebuild** to add/update models — write to gravenhollow NFS, pod sees it immediately (with `actimeo=600` cache, within 10 minutes) - **All-SSD + dual 10GbE** — VRM files (typically 5–30 MB) load in <100ms on LAN - **ReadOnlyMany** — multiple replicas can share the same PVC - Source `.blend` files and textures remain on Quobyte S3 (Kasm bucket) for the creation workflow; only promoted VRM exports land on gravenhollow #### Remote Serving (Cloudflare R2 CDN) Companions-chat is accessed externally via Cloudflare Tunnel → `envoy-internal`. Serving multi-MB VRM files through the tunnel works but adds latency and consumes tunnel bandwidth. Cloudflare R2 provides a better path: | | | |---|---| | **Bucket** | `avatar-models` on Cloudflare R2 | | **Custom domain** | `assets.daviestechlabs.io` (Cloudflare DNS, orange-clouded) | | **Free egress** | R2 has zero egress fees — ideal for large binary assets | | **Cache** | Cloudflare CDN caches at 300+ global PoPs; `Cache-Control: public, max-age=31536000, immutable` | | **Sync** | CronJob in cluster: `rclone sync gravenhollow-s3:avatar-models r2:avatar-models --checksum` | | **Auth** | Public read (models are not sensitive); write via R2 API token in Vault | ##### R2 Sync CronJob ```yaml apiVersion: batch/v1 kind: CronJob metadata: name: avatar-models-r2-sync namespace: ai-ml spec: schedule: "0 */6 * * *" # Every 6 hours jobTemplate: spec: template: spec: containers: - name: sync image: rclone/rclone:1.68 command: - rclone - sync - gravenhollow-s3:avatar-models - r2:avatar-models - --checksum - --transfers=4 - -v volumeMounts: - name: rclone-config mountPath: /config/rclone readOnly: true volumes: - name: rclone-config secret: secretName: rclone-r2-config restartPolicy: OnFailure ``` ##### rclone Config (ExternalSecret from Vault) ```ini [gravenhollow-s3] type = s3 provider = Other endpoint = https://gravenhollow.lab.daviestechlabs.io:30292 access_key_id = secret_access_key = [r2] type = s3 provider = Cloudflare endpoint = https://.r2.cloudflarestorage.com access_key_id = secret_access_key = region = auto ``` ##### Client-Side Routing The frontend detects whether the user is on LAN or remote and routes model fetches accordingly: ```javascript // avatar.js — model URL resolution function resolveModelURL(path) { // LAN users: serve from the Go server (NFS-backed, same origin) // Remote users: serve from Cloudflare R2 CDN const isLAN = location.hostname.endsWith('.lab.daviestechlabs.io'); if (isLAN) return path; // e.g. /assets/models/Companion-A.vrm return `https://assets.daviestechlabs.io${path.replace('/assets', '')}`; // → https://assets.daviestechlabs.io/models/Companion-A.vrm } ``` Alternatively, the Go server can set the model base URL via a template variable based on the `Host` header, keeping the logic server-side. #### Versioning Strategy VRM files are immutable once promoted — updated models get a new filename (e.g., `Companion-A-v2.vrm`) rather than overwriting. This ensures: - Cloudflare CDN cache never serves stale content - Rollback is trivial — point the allowlist back to the previous version - Browser `Cache-Control: immutable` works correctly #### Storage Tier Summary | Location | Purpose | Tier | Access | |----------|---------|------|--------| | Quobyte S3 (`kasm` bucket) | Working files: `.blend`, textures, WIP exports | Kasm rclone volume | Kasm sessions only | | gravenhollow NFS (`/avatar-models/`) | Production VRM models + animations | `nfs-fast` PVC (RO) | companions-frontend pod, LAN | | gravenhollow RustFS S3 (`avatar-models`) | Mirror of NFS dir for R2 sync source | S3 API | CronJob rclone | | Cloudflare R2 (`avatar-models`) | CDN-served copy for remote users | R2 public bucket | Global, zero egress fees | ## BlenderMCP Capabilities Used | MCP Tool | Avatar Workflow Use | |----------|-------------------| | `get_scene_info` | Inspect current scene before modifications | | `create_object` | Scaffold base meshes for characters | | `modify_object` | Adjust proportions, positions, bone placement | | `set_material` | Apply skin, hair, clothing materials | | `execute_blender_code` | Run VRM export scripts, batch operations, custom rigging | | `get_screenshot` | AI reviews viewport to understand current state | | `poly_haven_download` | Fetch HDRIs, textures for environment/materials | | `hyper3d_generate` | Generate base 3D models from text prompts via Hyper3D Rodin | ## Security Considerations * **Code execution:** BlenderMCP's `execute_blender_code` runs arbitrary Python in Blender. The Kasm session is sandboxed (DinD container with no cluster access), limiting blast radius. Always save before executing AI-generated code. * **Telemetry:** BlenderMCP collects anonymous telemetry by default. Disabled via `DISABLE_TELEMETRY=true` in the MCP server config. * **Network:** The TCP socket (port 9876) between the MCP server and Blender add-on is local to the session. If accessed remotely, ensure the connection is tunnelled or restricted. * **S3 credentials:** rclone volume plugin credentials are managed via Kasm storage mappings and the existing `kasm-agent` ExternalSecret — no new secrets required. * **R2 credentials:** Cloudflare R2 API token stored in Vault (`kv/data/cloudflare-r2`), accessed via ExternalSecret by the sync CronJob. Write-only scope — the CronJob uploads but cannot delete the bucket. * **Public R2 bucket:** Avatar models are public assets (served to any authenticated companions-chat user). No sensitive data in VRM files. R2 bucket is read-only public via custom domain; write access requires the API token. * **Model allowlist:** Even though models are served from NFS/R2, the server-side and client-side allowlists in companions-frontend gate which models users can actually select. Uploading a VRM to gravenhollow does not make it available without a code change. ## Pros and Cons of the Options ### Option 1 — BlenderMCP in Kasm + VS Code + Quobyte S3 + gravenhollow NFS + Cloudflare R2 * Good, because AI-assisted modelling reduces manual effort for avatar creation * Good, because assets persist in S3 across sessions and are accessible from CI * Good, because no new infrastructure — Kasm, rclone, Quobyte, gravenhollow, and Cloudflare are already deployed * Good, because VS Code MCP integration means one editor for code and 3D work * Good, because Kasm sandboxes Blender execution away from the cluster * Good, because NFS-fast serving decouples model assets from container images (no rebuild to add models) * Good, because Cloudflare R2 has zero egress fees and global CDN caching for remote users * Good, because immutable versioned filenames enable aggressive caching and trivial rollback * Bad, because BlenderMCP is a third-party tool with arbitrary code execution * Bad, because socket communication adds latency for remote Kasm sessions * Bad, because VRM rigging quality may require manual adjustment after AI scaffolding * Bad, because two-hop promotion path adds operational complexity ### Option 2 — Local Blender + BlenderMCP on developer laptop * Good, because lowest latency (everything local) * Good, because no Kasm dependency * Bad, because assets are local — no durable S3 storage without manual sync * Bad, because Blender + add-ons must be installed on every dev machine * Bad, because not reproducible across machines ### Option 3 — Hyper3D / Rodin cloud generation only * Good, because no Blender installation needed * Good, because fully prompt-driven model generation * Bad, because limited control over output — no fine-tuning materials, rigging, or proportions * Bad, because Hyper3D free tier has daily generation limits * Bad, because generated models require post-processing for VRM compliance (humanoid rig, expressions, visemes) * Bad, because vendor dependency for a core asset pipeline ### Option 4 — Manual Blender workflow (status quo) * Good, because full manual control * Good, because no new tooling * Bad, because slow — no AI assistance for repetitive modelling tasks * Bad, because no integration with the development workflow * Bad, because assets stored ad-hoc with no structured pipeline to companions-frontend ## Links * Related to [ADR-0046](0046-companions-frontend-architecture.md) (companions-frontend architecture — Three.js + VRM avatars) * Related to [ADR-0026](0026-storage-strategy.md) (storage strategy — gravenhollow NFS-fast, Quobyte S3, rclone) * Related to [ADR-0044](0044-dns-and-external-access.md) (DNS and external access — Cloudflare Tunnel, split-horizon) * Related to [ADR-0049](0049-self-hosted-productivity-suite.md) (Kasm Workspaces) * [BlenderMCP GitHub](https://github.com/ahujasid/blender-mcp) * [VRM Add-on for Blender](https://vrm-addon-for-blender.info/en/) * [VRM Specification](https://vrm.dev/en/) * [@pixiv/three-vrm](https://github.com/pixiv/three-vrm) (runtime loader used in companions-frontend) * [Poly Haven](https://polyhaven.com/) (free 3D assets, HDRIs, textures) * [Hyper3D Rodin](https://hyper3d.ai/) (AI 3D model generation) * [Cloudflare R2 Documentation](https://developers.cloudflare.com/r2/) * [Cloudflare R2 Custom Domains](https://developers.cloudflare.com/r2/buckets/public-buckets/#custom-domains)