Represent retro-reflective materials

[AdrienHerubel]

Retro-reflective surfaces are ubiquitous, especially in scenes representing urban and industrial environment, as those materials are commonly used for any equipment related to safety.

There has been extensive discussion on slack (see slack thread and slack thread) on the topic.

We have so far identified two possible approaches for representing retro-reflective materials in OpenPBR :

• New BSDF : see proposal Retro Reflective Node.pdf shadertoy implementation
• Modified NDF of the coating / main dielectric layer based on BRDF Measurements and Analysis of Retroreflective Materials shadertoy implementation

There are additional techniques commonly used to implement retro-reflective surfaces, based on shading normal modifications.

References :

• https://www.researchgate.net/publication/323012340_A_retroreflective_BRDF_model_based_on_prismatic_sheeting_and_microfacet_theory
• https://www.researchgate.net/publication/317575122_A_physically-based_BRDF_model_for_retroreflection
• https://www.researchgate.net/publication/316656998_Simulation_of_small-_and_wide-angle_scattering_properties_of_glass-bead_retroreflectors
• https://www.researchgate.net/publication/251610177_Photographic_assessment_of_retroreflective_film_properties
• https://www.artstation.com/blogs/d4ku/wZrD/a-retro-reflective-shader-for-unity
• BRDF Measurements and Analysis of Retroreflective Materials https://hal.science/hal-01083366/
• A brief history of retroreflective sign face sheet materials https://www.rema.org.uk/pub/pdf/history-retroreflective-materials.pdf