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Thread: Retro Reflective Surfaces in 2020

  1. #1
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    Retro Reflective Surfaces in 2020

    Any thoughts on creating surfaces such as velvet, moon regolith and other retro-reflective, surfaces in 2018 -> 2020 ?

    In 2015.3 we had Dpont velvet shader but that got removed for the newer renderer.

    I did a search but images are missing in the old topic on this subject so thought I would revisit it.

  2. #2
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    I would also love to see an accurate retro reflective shader, though I'm still on 2019.
    I was looking into it a while ago, but got lost pondering lambert shaders, gradient, dot products, etc, then got busy/gave up.

    Id love it to have an input for the reflectance angle, and work accurately in both 'day' and 'night' lighting conditions. I have no NEED for it, just an itching curiosity.


  3. #3
    Electron wrangler jwiede's Avatar
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    Here's a decent, modern starting point:

    Guo, Jie & Guo, Yan-wen & Pan, Jin-gui. (2018). A retroreflective BRDF model based on prismatic sheeting and microfacet theory. Graphical Models. 96. 10.1016/j.gmod.2018.01.002.

    We propose a novel reflectance model for the physically based rendering of retroreflective materials, based on prismatic sheeting and microfacet theory. Due to its high performance, prismatic sheeting has been extensively used in material industry. We show through a geometric optics analysis that a prismatic sheet with a smooth incident plane exhibits perfect retroreflection, and retroreflectivity varies with respect to the incident direction. To permit imperfect retroreflection that appears frequently in many common situations, we model the incident plane as a rough surface with a microfacet profile. By adjusting surface roughness, we can easily change the angularity of the retroreflection lobe. We analyze thoroughly the relationship between surface roughness and glossiness of retroreflection using joint spherical warping strategy. Based on the analysis, a practical BRDF model is derived for materials with a prismatic sheet which comprises a surface reflection term, a retroreflection term, and a diffuse reflection term.

    Paper on ResearchGate

    Cite and Paper on ACM DL

    And while we're on the topic of odd semi-retroreflective surfaces, another good paper (pun intended):

    Papas, Marios & de Mesa, Krystle & Jensen, Henrik. (2014). A Physically-Based BSDF for Modeling the Appearance of Paper. Computer Graphics Forum. 33. 10.1111/cgf.12420.

    We present a novel appearance model for paper. Based on our appearance measurements for matte and glossy paper, we find that paper exhibits a combination of subsurface scattering, specular reflection, retroreflection, and surface sheen. Classic microfacet and simple diffuse reflection models cannot simulate the double-sided appearance of a thin layer. Our novel BSDF model matches our measurements for paper and accounts for both reflection and transmission properties. At the core of the BSDF model is a method for converting a multi-layer subsurface scattering model (BSSRDF) into a BSDF, which allows us to retain physically-based absorption and scattering parameters obtained from the measurements. We also introduce a method for computing the amount of light available for subsurface scattering due to transmission through a rough dielectric surface. Our final model accounts for multiple scattering, single scattering, and surface reflection and is capable of rendering paper with varying levels of roughness and glossiness on both sides.

    Paper on ResearchGate

    Cite and Paper on ACM DL

    P.S. Props to ACM for making all ACM-published Digital Library content free to access through Jun 30, 2020!!
    Last edited by jwiede; 05-22-2020 at 05:05 PM.
    John W.
    LW2015.3UB/2019.1.5 on MacPro(12C/24T/10.13.6),64GB RAM, NV 980ti

  4. #4
    Not so newbie member lardbros's Avatar
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    Velvet can be done using the PBSDF shader… just use the 'sheen' amount. This can actually be overcranked way above 100% too. (This won't do retroreflective, but I'm certain with some nodal goodness, it wouldn't be that difficult).
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