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Thread: Transparency through two windows

  1. #1
    Audere-Est-Facere adrian's Avatar
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    Transparency through two windows

    Hi, so this is baffling me completely especially as things work as I would expect them to in LW11.6.3

    I have an object with two sets of windows, both have 95% transparency applied and you can quite clearly see inside the carriage so transparency must be working. Why then can I not see outside the far window? It just shows black. It doesn't matter whether the surface is set to double-sided or not, the "opaque" option is not checked.

    I am using LW2018, the material is standard, shading model set to photoreal, reflection set to raytrace+backdrop (not that it's relvant for this test render), refraction set to raytrace only.

    I'm guessing (hoping?) there must be a setting somewhere else I am not seeing that needs to be tweaked? The really crazy thing is even if I remove the far windows then I still only see black where I should see the outside!

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    Any help with this much appreciated
    Adrian.

    "Dreams are good, but memories are better"

  2. #2
    Super Member omichon's Avatar
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    Have you tried to increase Refraction Recursion Limit ?
    www.oliviermichon.fr | 3D Animation, Motion Graphics and Broadcast Design.

  3. #3
    Curmudgeon in Training Ma3rk's Avatar
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    If you use VPR, NOT in draft mode, you can increase the levels & look as you increase the limits to what you need. I find a 7-9 rage is generally good.
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  4. #4
    Audere-Est-Facere adrian's Avatar
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    Ah ok... no didn't think about that at all. I'll give it a go :-)
    Adrian.

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  5. #5
    Audere-Est-Facere adrian's Avatar
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    Sadly whatever setting I set refraction recursion limit to it makes no difference. I tried anything from 6 to 50, same result as above.
    Adrian.

    "Dreams are good, but memories are better"

  6. #6
    RETROGRADER prometheus's Avatar
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    Make sure also the refraction model is set to raytrace and backdrop in the shading model tab, same as you have in reflection options.
    all the other settings will give a none transparent result.

  7. #7
    what glass preset are you using, simple glass will work without issue, no black on second layer, but if you use something like diamond glass which uses dielectric you will get black on the second layer, you just have to ratchet up the transmittance distance till it goes away, er to really quite silly numbers, but it works

  8. #8
    RETROGRADER prometheus's Avatar
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    Quote Originally Posted by gerry_g View Post
    what glass preset are you using, simple glass will work without issue, no black on second layer, but if you use something like diamond glass which uses dielectric you will get black on the second layer, you just have to ratchet up the transmittance distance till it goes away, er to really quite silly numbers, but it works
    he said the material was standard material, so probably not dielectric.

  9. #9
    then I would strongly suggest he uses a preset such as simple glass, if that still screws up it won't be down to the glass it will be something else. Only thing that could throw off a glass look built with standard is if you add a value to the colour filter input that would make the second pane darker, but I've done railway carriages and have never had transmission problems with light not going all the way through

  10. #10
    Audere-Est-Facere adrian's Avatar
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    Tried all the suggestions above, nothing works. In fact I tried all the glass presets. This is just crazy.

    I've attached the object without textures as that would've made the file size massive and it doesn't matter whether textures are applied or not. Can anyone see something wrong that I can't? BTW I'm using 2018.0.7 and as I said in my original post the object renders fine in 11.6.3 which to me would suggest it's not a problem with the model, but of course I could be wrong.
    Attached Files Attached Files
    Adrian.

    "Dreams are good, but memories are better"

  11. #11
    With the PBR materials, you'll need to give your glass a thickness. Don't just use a single flat polygon. And you don't need double-sided activated.

    Starting around 4:30 in the video, it explains it in more detail.
    https://www.youtube.com/watch?v=saRXQ9VYWsw&t=461s

  12. #12
    I just tried your model. When I loaded your model, I just selected the window material and added a preset of "Simple Glass". And it looked fine.

    Then I selected all of the materials and converted them to Principled Nodes. Then I added the "Simple Glass" preset back onto the glass surface and rendered this still.

    I am using LW 2019.1.5. I can't remember if 2018 had any issues with transparency or not.
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  13. #13
    yes that makes sense, did think of the possibility you made it all as one object but thought nah, he wouldn't , would he ?............ glass should always be on a separate layer, 1/- for exclusion from things like radiosity, 2/- the ability to turn off cast shadow (both in object properties and not something you can do if it is applied as a shader only), the way you have done your glass will cause it to be treated as a volume for the purposes of refraction and absorption, this is really really undesirable, go separate them out, will still have to deal with absorption if you go PBR but in standard it should next to problem. And don't subpath when you can hard surface it's not cool, this was a far more economic approach in terms of file size
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  14. #14
    TrueArt Support
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    Quote Originally Posted by gerry_g View Post
    1/- for exclusion from things like radiosity,
    Ray Type = 7 is GI ray.

    Normal:
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    Detected and clipped:
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    You can also use Ray Switch.
    Normal (green replacement of GI to make it better visible):
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    Transparent material makes it invisible.
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    Quote Originally Posted by gerry_g View Post
    2/- the ability to turn off cast shadow (both in object properties and not something you can do if it is applied as a shader only),
    Ray Type = 4 is Shadow ray.

    Normal:
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    Shadows gone (clipped):
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  15. #15
    yes always wondered how you got that to work, thanks for that very illuminating , but not sure if that will change the fact that having the windows attached to the carriage causes it to behave like one great big volume with ridiculous refractive qualities, possibly you could zero that out, not sure

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