Function subtract_box

native/shared/src/geometry.rs:189–230

Subtract an axis-aligned box from existing geometry. This is a simplified CSG operation that clips triangles against a box. For Phase 2 MVP, we use a simple approach: remove triangles fully inside the box and clip intersecting ones. This handles the common case of door/window cutouts in walls. - `min`: box minimum corner [x, y, z] - `max`: box maximum corner [x, y, z]

(
    geo: &GeometryData,
    min: [f32; 3],
    max: [f32; 3],
)

/// - `min`: box minimum corner [x, y, z]
/// - `max`: box maximum corner [x, y, z]
pub fn subtract_box(
    geo: &GeometryData,
    min: [f32; 3],
    max: [f32; 3],
) -> GeometryData {
    let mut out_vertices = Vec::new();
    let mut out_indices = Vec::new();

    // Process each triangle
    for tri in geo.indices.chunks(3) {
        if tri.len() < 3 { continue; }
        let v0 = &geo.vertices[tri[0] as usize];
        let v1 = &geo.vertices[tri[1] as usize];
        let v2 = &geo.vertices[tri[2] as usize];

        // Check if any vertex is inside the box
        let in0 = point_in_box(&v0.position, &min, &max);
        let in1 = point_in_box(&v1.position, &min, &max);
        let in2 = point_in_box(&v2.position, &min, &max);

        if in0 && in1 && in2 {
            // Triangle fully inside box — discard
            continue;
        }

        // Triangle fully outside or partially intersecting — keep for now
        // (Full CSG clipping would split partial triangles, but for MVP
        //  removing fully-interior triangles handles most cutout cases)
        let base = out_vertices.len() as u32;
        out_vertices.push(*v0);
        out_vertices.push(*v1);
        out_vertices.push(*v2);
        out_indices.push(base);
        out_indices.push(base + 1);
        out_indices.push(base + 2);
    }

    GeometryData {
        vertices: out_vertices,
        indices: out_indices,
    }
}

fn point_in_box(p: &[f32; 3], min: &[f32; 3], max: &[f32; 3]) -> bool {
    p[0] >= min[0] && p[0] <= max[0]