Engine: Polymer has major issues rendering surfaces in NAM
This goes back to the very first versions of Polymer, and maybe the levels were badly designed.
The following screenshots were taken in the first level of NAM:
These floors seem to be rendered as parallax skies rather than grass. The sky also appears to be oddly shifted down.
Additionally, level geometry is visible through parallax skies in Polymer:
I know that Polymer isn't really maintained anymore, but this may be useful for projects that are based on Polymer, e.g. the experimental Direct3D 12/Vulkan renderer from ICD, should that ever go anywhere.