Compute a stable cache key. optionsJson should be a canonical serialization of the render options
that affect output (size, background, view, lighting) — the caller passes it so only output-affecting
fields are folded in. envId defaults to defaultEnvId.
Compute a stable cache key.
optionsJsonshould be a canonical serialization of the render options that affect output (size, background, view, lighting) — the caller passes it so only output-affecting fields are folded in.envIddefaults to defaultEnvId.