raytracer_memincrease_fix_2

raytracer_memincrease_fix_2.rs

// For the sake of brevity I won't repeat the code we replace here instead point out
// that this replaces lines 307-328 in our original code 

const BYTES_PER_PIXEL: usize = 3;
fn main() {
// {...}
    // first allocate a zeroed Vec<u8> to hold our results. 
    // btw: this initialization method is the fastest way to ask 
    // for zeroed memory: see https://github.com/rust-lang/rust/issues/54628
    let mut bytes = vec![0u8; h as usize * w as usize * BYTES_PER_PIXEL];
    bytes
        // take mutable chunks of three items
        .par_chunks_mut(BYTES_PER_PIXEL)
        // Turn this into a parallel iterator using Rayon
        .into_par_iter()
        // reverse the order in which we iterate so our picture doesn't end upside down
        .rev()
        // enumerate() changes the closure argument from |item| => |(index, item)| tuple
        .enumerate()
        .for_each(|(idx, chunk)| {
            // determine the x- and y-coordinates based on the index in row-major order
            // https://en.wikipedia.org/wiki/Row-major_order
            let y = (idx / w as usize) as f32;
            let x = (idx % w as usize) as f32;
            let mut color = Vec3::from(0.0);
            for _ in 0..samples_count {
                color = color
                    + trace(
                        position,
                        !(goal
                            + left * (x - w / 2.0 + random_val()).into()
                            + up * (y - h / 2.0 + random_val()).into()),
                    );
            }

            color = color * (1.0 / samples_count as f32).into() + (14.0 / 241.0).into();

            let o: Vec3 = color + Vec3::from(1.0);
            color = Vec3::new_abc(color.x / o.x, color.y / o.y, color.z / o.z) * Vec3::from(255.0);
            // We write the new values to our buffer
            chunk[0] = color.x as u8;
            chunk[1] = color.y as u8;
            chunk[2] = color.z as u8;
        });

    file.write_all(&bytes).unwrap();
}