Function reflection_matrix

native/shared/src/renderer/planar_reflection.rs:131–143

Build the world-space reflection matrix for plane (n, plane_y). Reflects a world-space point `p` across the plane `n · p = d` where `d = n · (0, plane_y, 0) = n.y * plane_y`. The returned 4×4 matrix R has `R · p = p - 2 (n·p - d) n`, with R applied post-multiply on column vectors (Bloom convention). Plug this into the view chain via `mirror_view = view * R` — post-multiplying R into the view mat

(plane_y: f32, normal: [f32; 3])

/// post-multiplying R into the view matrix means: world → mirror
/// (R) → camera (view).
pub fn reflection_matrix(plane_y: f32, normal: [f32; 3]) -> [[f32; 4]; 4] {
    let n = normalise(normal);
    let d = n[1] * plane_y;
    // Standard Householder-style reflection across the plane.
    // Column-major; multiplies p as `R * p` (post-mul).
    let nx = n[0]; let ny = n[1]; let nz = n[2];
    [
        [1.0 - 2.0 * nx * nx, -2.0 * nx * ny,       -2.0 * nx * nz,       0.0],
        [-2.0 * ny * nx,        1.0 - 2.0 * ny * ny, -2.0 * ny * nz,       0.0],
        [-2.0 * nz * nx,       -2.0 * nz * ny,        1.0 - 2.0 * nz * nz, 0.0],
        [2.0 * nx * d,          2.0 * ny * d,         2.0 * nz * d,         1.0],
    ]
}

/// Compose a mirrored view matrix from the camera's current view
/// matrix and the reflection plane.