Retro-Reflective Shader
Showing off the high tech materials of the Brooks Aurora running shoe in this spot was key. One of the most interesting materials used is a retro-reflective coated fabric. This is the shader I created to simulate that material. To achieve this effect I layered two PBR materials onto one another, with one having modified surface normals that essentially “flattened“ it in screenspace, so that when a light was in line with the camera the object would be mostly reflecting that light directly back to the source. Layered additively on top of a traditional PBR material material, it resulted in a PBR shader that had a clearcoat of retro-reflective material on the surface.
To really sell the effect I recreated the slight imperfections with the coating that resulted in a metallic flake like sparkle when the light was near dead-on to the surface. The parametric material can be tweaked to adjust the strength of the retro-reflectivity and adjust the flake scale and frequency.
Because this shader does not rely on knowing the position of any light sources, it will work in any scene and even with multiple light-sources, and maintain plausible physically realistic appearance.
Right before the light source reaches dead on, the flakes become apparent, giving the material an interesting surface texture.
With 0° angle of incidence to the light source, nearly 100% of the light is being reflected back at the camera.
Node tree showing the modification of surface normals being used in a secondary materials bump channel input to fake the retro-reflectivity.