Screenshot from the glTF Sample Viewer with the Wide Street environment light.
This model is a sphere using the glTF extension KHR_materials_clearcoat overtop a car paint base material.
The base material is meant to mimic the scattering from micro flakes such as used in some car paints.
The model uses a single bitmap for the normal bump texture with a random per-pixel noise pattern, and the glTF extension KHR_texture_transform to increase bump tiling.
The normal bump texture, enlarged 200% to show detail.
Roughness was increased to 0.4 to scatter the reflected light and to provide a contrast with the clear coat layer which uses zero Roughness. Metalness was set arbitrarily to a partial value of 0.3 to increase the specularity of the base material.
CC0, No Rights Reserved, https://creativecommons.org/share-your-work/public-domain/cc0/. Model and texture created by Eric Chadwick.