4 ms·

> “But when the material is full of defects, a failure cannot easily propagate from one grain boundary to the next. That means the material won't suddenly fail

> “But when the material is full of defects, a failure cannot easily propagate from one grain boundary to the next. That means the material won't suddenly fail because the deformation becomes distributed more evenly throughout the material.” Disordered structure gives glass its strength but also its transparency. I wonder if this stuff is transparent or if the fact that it is made out of metal would prevent that.

xeonmc 3y ago
If you think in terms of PBR rendering: * refractive index determines the split between reflected and refracted light vs angles. * diffuse albedo determines the absorption of refracted light. * specular albedo determines the absorption of reflected light. * opacity determines the scattering of refracted light. * roughness determines the scattering of reflected light. In PBR, metals are modeled with a purely black diffuse albedo (with very high refractive index), while dielectrics are modeled with a purely white specular albedo. A transparent dielectric means all the refracted light goes straight, while a opaque white dielectric means all the refracted light are scattered (but not absorbed!) For metals, it doesn't really matter whether the refracted light is scattered or not, if they're all gonna be absorbed anyways. --- EDIT: laying out the parameters like this, I just realized why Unreal Engine's PBR felt "off" at times -- their "metalness" workflow does not allow you to adjust the refractive index of metals! I'm guessing they just assume that metals have infinite refractive index and so the refraction-reflection split is 0%-100% with no angle dependence. This means that they are generally overestimating how shiny metals should look with no Fresnel effect at all.
- davidhyde 3y ago
  Very insightful, thank you! I always wondered about transparent aluminium but I see that it is actually a ceramic and not elemental. https://en.m.wikipedia.org/wiki/Aluminium_oxynitride https://en.m.wikipedia.org/wiki/Aluminium_oxynitride
  - hutzlibu 3y ago
    But a very interesting ceramic, with the patents guarding the manufacture expired it seems.

xeonmc 3y ago

If you think in terms of PBR rendering: * refractive index determines the split between reflected and refracted light vs angles. * diffuse albedo determines the absorption of refracted light. * specular albedo determines the absorption of reflected light. * opacity determines the scattering of refracted light. * roughness determines the scattering of reflected light. In PBR, metals are modeled with a purely black diffuse albedo (with very high refractive index), while dielectrics are modeled with a purely white specular albedo. A transparent dielectric means all the refracted light goes straight, while a opaque white dielectric means all the refracted light are scattered (but not absorbed!) For metals, it doesn't really matter whether the refracted light is scattered or not, if they're all gonna be absorbed anyways. --- EDIT: laying out the parameters like this, I just realized why Unreal Engine's PBR felt "off" at times -- their "metalness" workflow does not allow you to adjust the refractive index of metals! I'm guessing they just assume that metals have infinite refractive index and so the refraction-reflection split is 0%-100% with no angle dependence. This means that they are generally overestimating how shiny metals should look with no Fresnel effect at all.

davidhyde 3y ago
Very insightful, thank you! I always wondered about transparent aluminium but I see that it is actually a ceramic and not elemental. https://en.m.wikipedia.org/wiki/Aluminium_oxynitride https://en.m.wikipedia.org/wiki/Aluminium_oxynitride
- hutzlibu 3y ago
  But a very interesting ceramic, with the patents guarding the manufacture expired it seems.