Function render_until_silent 

pub fn render_until_silent(
    graph: &Graph,
    target: &str,
    config: RenderConfig,
    silent: Silent,
    cache: Option<&dyn Cache>,
    slots: Option<&Slots>,
) -> Result<Render, EngineError>

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.