| name | renderer-constrained-backend |
| description | Build a renderer backend to a hard resource or capability budget — low VRAM, raster-only (no hardware ray tracing), or a portable/embedded GPU like OpenGL ES — where features must be baked, capped, or degraded rather than ported wholesale from the high-end backend. Use when Codex builds a low-end/portable backend, fits a GPU-memory budget, bakes materials instead of codegen, or makes a no-RT fallback match a reference renderer. |
Renderer Constrained Backend
Purpose
A low-end backend — tight VRAM, no hardware ray tracing, a portable GPU such as OpenGL ES — is a deliberate target, not a degraded copy of the reference renderer. Its constraints change the architecture, not just a quality knob: what you bake vs. generate, what you cap, what you approximate. Each of those must be a code invariant and stay comparable to the reference, or the backend is "correct but visibly different" — which derails parity for reasons that read as bugs. Pairs with renderer-target-architecture-design (name the target first) and renderer-realtime-sensor (the fidelity/throughput/memory dial).
Budget is an invariant enforced at upload, not an aspiration
- A "<100 MB GPU" target is met by a hard, central cap applied at load time — clamp texture resolution and box-downsample anything over the cap, exposed as one tunable. Warehouse-scale USD ships 2K–4K textures that blow a low-VRAM budget instantly; nothing downstream guarantees the budget unless the clamp does. Make the budget a code invariant, not a README line.
Material strategy differs from the high-end backend — bake, don't codegen
- A constrained raster backend resolves MaterialX by walking the node graph and baking its
<image> and procedural nodes into fixed UsdPreviewSurface-shaped texture slots — deliberately not generating a shader per material. The high-end backend's per-material shader codegen would inherit pipeline-count explosion and a uniform-model mismatch on the constrained target. These are material architectures; do not mirror the codegen path onto the constrained backend.
