CubeMap Mip for Global Illumination

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This technique is imitation of Unreal’s Sphere Reflection Capture Actor .
Each reflection actor generates Mip Cubemaps, according to the roughness of the object. 

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If objects fall within the bounds of the reflection actor, they are starting to use the cubemaps of the reflection actor as their environment map.
If an object is affected by multiple reflection actors, the cube map of the reflection actor with the largest radius will be sent to the back.
In other words, the environment map of the reflection actor with the smallest radius range has the most priority to be seen.

 

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<Roughness>                                                                                                             <Reflection by CubeMap Mip>

The smaller roughness of an object, the more clear cube map is used.