High Dynamic Range (HDR)

Checked with version: 5.1

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Difficulty: Beginner

As well as Color Space, the ‘dynamic range’ of your camera needs to be configured. Essentially, this defines how extremely bright or dark colors are captured by scene cameras. HDR can be enabled from the camera component in the Inspector by using the HDR checkbox. Note that HDR is unsupported by some mobile hardware. It is also not supported in Forward Rendering when using techniques such as multi-sample anti-aliasing (MSAA).

HDR is best used in combination with Linear Color Space in order to preserve accuracy when handling very bright colors.

By default, cameras in Unity use a Low Dynamic Range (LDR). Colors are stored using 8-bits per channel - red, green and blue. 8-bits refers to the ‘precision’ and means that color data is stored with 8 values of either 1 or 0, giving 256 possible unique combinations for each color channel. 256 x 256 x 256 colors per channel means that by storing values using 8-bits we are able to uniquely reference over 16 million color variations ranging in intensity from black to white.

In reality, colors in the real world extend far outside this 16 million color range. There are infinite permutations of color possibilities, and brightness goes beyond what our eyes can even see. Similarly Unity is capable of handling extremely bright lights which produce colors beyond that which can be displayed on an LDR device such as your computer screen. However, despite this potential limitation in the output device, these extreme light values still remain useful to us in a number of applications.

By enabling HDR on your scene camera, colors will be stored with much greater precision (using the floating point representation). Many more unique colors over a much brighter range of luminance can be handled.

HDR enables us to preserve the great differences in brightness between, say, outdoor lighting in our scenes and shaded areas. We can also create effects like ‘blooms’ or glows by applying effects to these bright colors in your scene. Special effects like these can add realism to particles or other visible light sources. However, these extreme color values also need to be handled somehow to prevent them being ‘clamped’ to white.