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fix: safe i32-to-usize casts in AO sampling #2

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Merged
LachyFS merged 1 commit into from
Apr 1, 2026
Merged

fix: safe i32-to-usize casts in AO sampling #2

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54 changes: 37 additions & 17 deletions crates/urath-core/src/ao.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,16 @@ pub fn vertex_ao(side1: bool, side2: bool, corner: bool) -> u8 {
3 - (side1 as u8 + side2 as u8 + corner as u8)
}

/// Convert a signed coordinate to `usize` only if it lies in `[0, size)`.
#[inline]
fn coord_as_usize(val: i32, size: i32) -> Option<usize> {
if val >= 0 && val < size {
Some(val as usize)
} else {
None
}
}

/// Sample whether a block at signed coordinates is opaque.
///
/// Handles coordinates outside the chunk bounds by reading from `neighbors`.
Expand All @@ -34,30 +44,40 @@ pub fn sample_block_opaque(
let size = chunk.size() as i32;

// Within chunk bounds
if x >= 0 && x < size && y >= 0 && y < size && z >= 0 && z < size {
return registry.is_opaque(chunk.get(x as usize, y as usize, z as usize));
if let (Some(ux), Some(uy), Some(uz)) = (
coord_as_usize(x, size),
coord_as_usize(y, size),
coord_as_usize(z, size),
) {
return registry.is_opaque(chunk.get(ux, uy, uz));
}

// Outside chunk — check neighbors
// For simplicity, only handle the case where exactly one axis is out of bounds
// (corner/edge neighbors are treated as air)
if x < 0 && y >= 0 && y < size && z >= 0 && z < size {
return registry.is_opaque(neighbors.get_border_block(Face::NegX, z as usize, y as usize));
}
if x >= size && y >= 0 && y < size && z >= 0 && z < size {
return registry.is_opaque(neighbors.get_border_block(Face::PosX, z as usize, y as usize));
}
if y < 0 && x >= 0 && x < size && z >= 0 && z < size {
return registry.is_opaque(neighbors.get_border_block(Face::NegY, x as usize, z as usize));
}
if y >= size && x >= 0 && x < size && z >= 0 && z < size {
return registry.is_opaque(neighbors.get_border_block(Face::PosY, x as usize, z as usize));
if let (Some(uy), Some(uz)) = (coord_as_usize(y, size), coord_as_usize(z, size)) {
if x < 0 {
return registry.is_opaque(neighbors.get_border_block(Face::NegX, uz, uy));
}
if x >= size {
return registry.is_opaque(neighbors.get_border_block(Face::PosX, uz, uy));
}
}
if z < 0 && x >= 0 && x < size && y >= 0 && y < size {
return registry.is_opaque(neighbors.get_border_block(Face::NegZ, x as usize, y as usize));
if let (Some(ux), Some(uz)) = (coord_as_usize(x, size), coord_as_usize(z, size)) {
if y < 0 {
return registry.is_opaque(neighbors.get_border_block(Face::NegY, ux, uz));
}
if y >= size {
return registry.is_opaque(neighbors.get_border_block(Face::PosY, ux, uz));
}
}
if z >= size && x >= 0 && x < size && y >= 0 && y < size {
return registry.is_opaque(neighbors.get_border_block(Face::PosZ, x as usize, y as usize));
if let (Some(ux), Some(uy)) = (coord_as_usize(x, size), coord_as_usize(y, size)) {
if z < 0 {
return registry.is_opaque(neighbors.get_border_block(Face::NegZ, ux, uy));
}
if z >= size {
return registry.is_opaque(neighbors.get_border_block(Face::PosZ, ux, uy));
}
}

// Edge/corner neighbor — treat as air
Expand Down
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