Description

PMREM filters the environment map based on roughness, but for a mirrored object (metal = 1, rough = 0), it should reflect the environment unchanged. This is not the case, as even the full-res PMREM environment has gone through one filtering pass, resulting in artifacts.

Live Demo

https://googlewebcomponents.github.io/model-viewer/examples/model-formats.html

The default, without PMREM (original environment):

Adding the experimental-pmrem attribute, which should be identical since this model is metal = 1, rough = 0: