A finite, declarative family of compile-time graph alternatives. Each key
selects a complete graph, so inactive branches consume no uniforms,
samplers, instructions, or render-target dependencies. Backend caches still
share identical source between variants; distinct source gets its own GPU
program. Variant selection is explicit authoring work, never a frame-time
compilation flag hidden in mutable material state.
A finite, declarative family of compile-time graph alternatives. Each key selects a complete graph, so inactive branches consume no uniforms, samplers, instructions, or render-target dependencies. Backend caches still share identical source between variants; distinct source gets its own GPU program. Variant selection is explicit authoring work, never a frame-time compilation flag hidden in mutable material state.