Function defines 

pub fn defines(
    _program: &Program,
    platform: Platform,
    pool_size: usize,
    probe_count: usize,
) -> Vec<(&'static str, String)>

The variant defines for one entry on one host. pool_size and probe_count are the bindless texture-pool length and the probe cube array length the Vulkan host declares; the cook bakes the ceilings and a device that cannot seat them recompiles, exactly as the engine’s own bindless programs do. Metal and DirectX bind fixed counts.