Function mat_mul

tools/imposter-baker/src/render.rs:479–492

(a: [[f32; 4]; 4], b: [[f32; 4]; 4])

}

fn mat_mul(a: [[f32; 4]; 4], b: [[f32; 4]; 4]) -> [[f32; 4]; 4] {
    // Column-major: result[col][row] = sum_k a[k][row] * b[col][k]
    let mut out = [[0.0; 4]; 4];
    for col in 0..4 {
        for row in 0..4 {
            let mut s = 0.0;
            for k in 0..4 {
                s += a[k][row] * b[col][k];
            }
            out[col][row] = s;
        }
    }
    out
}

// ────────────────────────────────────────────────────────────────────
// WGSL: vertex stage shared, three fragment outputs (lambert / normal /