Glass Refraction Settings...

  • Hi folks,

    I wonder if anyone could recommend refraction settings for a pane of glass roughly two inches thick, please? I can't seem to get it right. Also, if someone could explain how I would go about making the glass really appear thick, as though it gets less transparent at shallower angles, just as real glass does, I'd be very grateful.

  • Big assumption you are using Superfly

    Take a look at super-fly-coloured-glass If you want clear glass just set the absorption colour to white or delete the absorption node altogether

    and for refraction settings

  • Thank you, but I'm using Firefly. Should have mentioned that, my bad. :P

  • Poser Ambassadors

    Because there have been numerous changes over the years, exactly the best way to handle glass has changed as well. So I'd need to know specifically WHICH Poser you intend to use. Just saying FireFly doesn't qualify it sufficiently.

    Some general points to know about FireFly and glass that may affect how we build the shader:

    For most of Poser history, inverse refraction through the back side of a solid glass object (i.e. the ray is exiting the glass volume) was done incorrectly, and the refraction would take place as if it was entering. This resulted in double the visible shift of objects seen through the glass. I no longer remember which version corrected this.

    For most of Poser history, total internal reflection within the back side of a solid glass object (i.e. the ray does not exit the glass volume at shallow angles) was not implemented in FireFly. I no longer remember which version corrected this.

    For all of Poser history, FireFly does not do caustics and will create the appearance of a solid shadow as if the glass is completely opaque. Sometimes we use transparency instead of refraction as a workaround, when the amount of image shifting is really tiny anyway, such as any window glass.

    The "best" node for glass in FireFly (Fresnel) has, at times, produced double refractions making it useless. And for all time it was useless for colored glass, as it also applies the coloring to the reflections which is an outright violation of physics.

  • I remember seeing something from Bagginsbill a while back but searching unearths nothing. Perhaps it was on RDNA...

    Are you there, BB? I think you'd be the best chap to ask about this.

    I've tried using edited versions of the materials from Exnem's Glass Ensemble (removing the maps and adjusting the IOR) but I'm getting all kinds of wacky results.

    I seem to remember settings needing to be different depending on exactly what the object is meant to be; so a small whisky glass would use a different setting to a large car windscreen, for example.

    For this project, I am using SledgeHammer's Crystal Cage, which is a large, metal framed cubicle with glass panels. These panels seem to be the thickness I mentioned, but the original shader is basic and not what I'm looking for.

  • Apologies, BB, you got here before I realised, lol! I'm using PP2014. Yes, I remember you mentioning these things before. If we were just talking about a window or some such, I would settle for my existing shader, which I use for cars etc, but this structure has glass which is quite thick. It's very much akin to the swanky looking bathroom I've had for years and can't remember the name of; loads of thick glass and neat lighting, but I can't get it looking right for the life of me, so this project may well create a shader I can use there too, which would be awesome.

    I should have a test render out fairly soon, though that's a killer too, as it's taking ages to render (ten hours so far).

  • Poser Ambassadors

    Try this. Remember, FireFly doesn't pass lighting through refraction - we just "see" through it.

    I turned off shadows for the glass pane (which is exactly 2 Poser inches thick). If your glass is part of a larger prop and you can't turn off its shadow, then I'd use the grouping tool to spawn the glass part(s) as a separate prop, then make the original glass 100% transparent and use the glass shader on the spawned part.


    Having the glass cast absolutely no shadow isn't correct but it's better than being solid opaque for lighting. If you've cloned the glass to make a spawned prop, you can make the original glass less than 100% transparent and then you'd have something closer to reality.

    Here's a better glass simulation but it's done with SuperFly.


  • Poser Ambassadors

    You mentioned being less transparent at shallower angles. The Fresnel effect, if applied properly, is responsible for most of that and it should take place as you turn the glass.

    The rest of it is volumetric absorption which is difficult to do with FireFly and is always going to be a hand-adjusted cheat. Volumetric absorption is also what makes the edges of glass rectangles look blue-green.

    I didn't deal with volumes in either the FireFly or SuperFly render above.

  • Poser Ambassadors

    Viewed from a more shallow angle, the glass transmits less light.

  • Thank you very much for that, it seems to have worked nicely, however, I did have to change the IOR on the refract node to a far lower level for this. I think it's ok, but I'll have to do a full render to see the results.

  • First render done and it looks good, thank you. The only thing that seems to be quirky is that I'm losing a lot of fine detail through the glass at all angles. Bit odd.

  • Poser Ambassadors

    If you have to lower the IOR it may be that your version of Poser still has the back-side refraction bug that goes in the wrong direction. When that was the case I used to set the refraction IOR really close to 1. As I don't recall when or if that got fixed before Poser 11, you might want to check if you're using the latest SR of PP2014.

    Losing texture detail seen through the refraction was encountered before. Try turning off texture filtering on the texture seen through the glass.

  • Poser Ambassadors

    I opened up PP2014 to confirm my suggestion about texture filtering.

    Here the stone has texture filtering set to None.


    vs. the terrible blur you get with texture filtering set to Quality


  • I'll try that, thank you. I know I've used filtering on my characters through EZSkin 2, which I've set to crisp, but I've just had a bash at the hair, which is HR-127 by Ali. I've had a mess around with it and hope I've fixed it, but I didn't deliberately add any filtering to it. It was showing up with odd trans mapping (the transparent areas were rendered as slightly transparent but without any maps, resulting in a beige band around the hairline). I'll keep you posted, thank you very much!

  • in your ff settings, how many raytrace bounces have you got? if you are seeing the hair through a refracting piece of glass then you are going to need more bounces for the transparent hair to show correctly

  • Poser Ambassadors

    In FireFly, raytrace bounce limits don't apply to transparencies. They do in SuperFly but that's because in SuperFly every interaction (transparent or refractive or reflective) is done by spawning an additional ray. FF doesn't spawn rays for transparency.

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