Fail-closed provider access
Public generation stays off unless an allowlist or explicit production flag is configured.
Product engineering case study · 2026
AI 3D generation with the expensive paths kept behind the server.
Renderivo is a private-source, pre-revenue product asset for turning text or a reference image into an inspectable 3D model. I designed the workflow around ownership, cost control and recoverable asynchronous jobs—not a happy-path demo.
4
provider routes
2
input modes
0
client credit writes
4 MB
image ceiling
System flow
One job, four guarded transitions.
- 01
Authenticate the operator
Firebase Auth establishes identity. Live provider jobs require a verified email, and Firestore rules keep user and generation records owner-scoped.
- 02
Reserve cost before work
The server checks plan access, concurrent work and hourly limits before reserving credits. Browser clients never write plan, credit or generation state.
- 03
Run an asynchronous job
Text or image input is submitted to one of four fal.ai routes. Authenticated polling and a signed callback converge on one server-owned status record.
- 04
Persist and inspect the result
Completed output can be copied to Vercel Blob, opened as a GLB with the bundled model-viewer component, and downloaded in provider-returned formats.
Engineering decisions
Controls that survive the demo.
The private repository keeps secrets and ownership changes on the server. These are implementation claims documented in the current source and release notes—not customer or revenue claims.
Two-part callback verification
A generation-scoped HMAC is checked alongside fal.ai Ed25519 JWKS verification, the raw body, timestamp and request ID.
Server-owned entitlements
Firebase Admin owns plan, credits, free usage and generation writes; client rules deny those mutations.
Recoverable accounting
Credits are reserved before submission, reconciled after interrupted jobs and refunded on eligible failures.
Stack
Deliberately conventional at the edges.
Next.js 16.2React 19TypeScriptFirebase AuthFirestorefal.ai queuesVercel BlobPaddleVitest
Verification surface
Checks are part of the handover.
- Type checking, lint, production build and Vitest commands are defined in the repository.
- A backend configuration check reports Firebase and provider readiness without printing secrets or customer data.
- The provider smoke test requires an explicit cost-confirmation flag before it can submit a paid generation.
Available paths
Acquire Renderivo, license the foundation, or hire me to build the next one.
The full Renderivo software asset is offered at $5,000. A separate brand-neutral 3D Studio Foundation is available from $499 under a non-exclusive licence.