build-up of luminance

例句：

1. 1. The sun's rays are building up the luminance of the sky.
   太阳的光线正在增加天空的亮度。
2. 2. The film has a luminous build-up at the end, which is quite captivating.
   这部电影在结尾处有一个非常吸引人的亮度积累。
3. 3. The scientist noticed that the luminance of the light source was gradually increasing.
   科学家注意到光源的亮度正在逐渐增加。