Function evaluate 

pub fn evaluate(
    shader: &dyn PixelShader,
    constants: &Constants,
    textures: &Views,
    inputs: &BTreeMap<(String, u32), Input>,
    grid: Grid,
    targets: &[(u32, u8)],
) -> Result<Evaluation, Error>

Evaluate shader once per grid pixel (Invocation::Scalar). textures are as evaluate_raw takes them. inputs are by (semantic, index), compared case-insensitively; a used input without one is an error. targets are (output register, required component mask); a target written at some pixels only is an error.