HDRI拥有比普通RGB格式图像（仅8bit的亮度范围）更大的亮度范围。

标准的RGB图像最大亮度是值是255/255/255，如果用这样的图像结合光能传递照明一个场景的话，即使是最亮的白色也不足以提供足够的照明来模拟真实世界中的情况，渲染结果看上去会平淡而缺乏对比，原因是这种图像文件将现实中的大范围的照明信息仅用一个8bit的RGB图像描述。

但是使用HDRI的话，相当于将太阳光的亮度值（比如6000%）加到光能传递计算以及反射的渲染中，得到的渲染结果也是非常真实和漂亮的。

下面的两张渲染的图片可以看出使用HDRI后带来的巨大差异。

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