A target rendered from the grid’s first sample on, one block at a time: every block is the
samples a whole render over the same rows writes there, bit for bit.
One reading off a buffer nothing rendered — an external file, say — under the profile the
caller names. Every representation needing the graph behind it refuses here.
The ledger over the part of a render over names: the same tree and the same shares,
each summed over those samples alone, as a render over that window alone would sum them.
The horizon ends at the last sample at or over the threshold. The bound proves every sample
from its grid instant on is under it, and the render between proves the rest.