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harenae-rs
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Add comments to update system

This commit is contained in:
Jarrod Doyle 2024-01-31 12:39:05 +00:00
parent 7a9839d402
commit b050fce637
Signed by: Jayrude
GPG Key ID: 38B57B16E7C0ADF7
1 changed files with 9 additions and 1 deletions
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10
src/falling_sand/mod.rs
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@ -182,7 +182,7 @@ pub fn simulate_chunk_system(mut chunk: Query<&mut Chunk>) {
let mut chunk = chunk.unwrap();
// Simulate sand
// Determine which Margolus neighbourhood offset we're using this update
let offset = if chunk.step == 0 {
(0, 0)
} else if chunk.step == 1 {
@ -194,11 +194,16 @@ pub fn simulate_chunk_system(mut chunk: Query<&mut Chunk>) {
};
chunk.step = (chunk.step + 1) % 4;
// We're operating on 2x2 blocks of cells
for block_y in 0..(chunk.height / 2) {
let y = block_y * 2 + offset.1;
for block_x in 0..(chunk.width / 2) {
let x = block_x * 2 + offset.0;
// Get all the cells in our block and convert them to a rule state for lookup
// Because our offset can cause cell look-ups to go ourside of the grid we have
// a default `Element::None`
// Cells are obtained in the order top-left, top-right, bottom-left, bottom-right
let start_state = to_rule_state((
chunk.get_cell(x, y + 1).unwrap_or(Element::None),
chunk.get_cell(x + 1, y + 1).unwrap_or(Element::None),
@ -206,6 +211,9 @@ pub fn simulate_chunk_system(mut chunk: Query<&mut Chunk>) {
chunk.get_cell(x + 1, y).unwrap_or(Element::None),
));
let end_state = chunk.get_rule_result(start_state);
// We only need to actually update things if the state changed
// Same ordering as above.
if start_state != end_state {
if (start_state & 0xFF000000) != (end_state & 0xFF000000) {
chunk.set_cell(x, y + 1, Element::from((start_state >> 24) & 0xFF));