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For image-based lighting from supplied environment maps, the specular reflection for dark, smooth, dielectric surfaces is too dark.
A smooth surface should reflect some of the light from the environment. At wide reflection angles, where the light from the source just glances against the surface before continuing to the eye position, a smooth surface is almost 100% reflective. The above image should look more like this:
Notice the faint reflection of the environment map in each sphere.
The current calculation of the specular reflection is as follows:
The additional f0 factor at the end looks like a mistake. The f0 color is already incorporated in the Fresnel term F, which is equal to f0 at normal incidence, but transitions toward a white reflectivity at glancing incidence. Removing the extra f0 factor would make the environment map lighting more consistent with our direct lighting, and also more consistent with other PBR implementations and PBR theory.
What happened?
For image-based lighting from supplied environment maps, the specular reflection for dark, smooth, dielectric surfaces is too dark.
A smooth surface should reflect some of the light from the environment. At wide reflection angles, where the light from the source just glances against the surface before continuing to the eye position, a smooth surface is almost 100% reflective. The above image should look more like this:
Notice the faint reflection of the environment map in each sphere.
The current calculation of the specular reflection is as follows:
The additional
f0
factor at the end looks like a mistake. Thef0
color is already incorporated in the Fresnel termF
, which is equal tof0
at normal incidence, but transitions toward a white reflectivity at glancing incidence. Removing the extraf0
factor would make the environment map lighting more consistent with our direct lighting, and also more consistent with other PBR implementations and PBR theory.Reproduction steps
Sandcastle example
http://localhost:8080/Apps/Sandcastle/index.html#c=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
Environment
Browser: Chrome
CesiumJS Version: 1.117
Operating System: Windows
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