normal line的用法和樣例：
例句
- The vertical line meets the horizontal one here.
垂直線與水平線在此相交。 - "A science fiction cannot not be regarded as a mere entertainment, but in fact it tells the reader much more."
"科幻小說不能簡單地看成是供消遣的，而實際上它給讀者展示更深刻的內容。" - This is necessary for normal mapping to work.
這是法線貼圖運作時所必須的。 - Vertex format includes a vertex normal vector.
頂點格式包括頂點法線向量。
