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2Sided Material + Refraction results in weird reflection component without thin-walled checked

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  • 2Sided Material + Refraction results in weird reflection component without thin-walled checked

    I'm not sure if this is a bug or not but it seems like this used to work differently (at least in prior versions from what I can remember). If I have a typical 2 sided material set up and the front material has any refraction (i.e, not 0,0,0), I get odd reflections showing up on the surfaces (the front material has NO reflections). If I check "thin-walled" everything works pretty much as expected though. Since it's easy to just check the "thin-walled" option for new materials, my main concern is for older scenes that I render or merge into newer ones. See the examples below:

    Click image for larger version

Name:	2Sided-Thin Wall OFF.jpg
Views:	158
Size:	27.8 KB
ID:	1174826 Click image for larger version

Name:	2Sided-Reflection Filter.jpg
Views:	187
Size:	17.2 KB
ID:	1174819 Click image for larger version

Name:	2Sided-Thin Wall ON.jpg
Views:	147
Size:	28.3 KB
ID:	1174828 Click image for larger version

Name:	VrayMtl-Thin Wall OFF.jpg
Views:	139
Size:	28.6 KB
ID:	1174829

    The scene is pretty simple with just a couple of shapes. You can see in the first image how the reflections appear and are absent when thin wall is ON. I did a another test where the front materials is pulled out so it's just a standard material, still with think walled off, and it renders fine. Scene attached as well, 2Sided Test.zip . BTW this is on 6.1.

    Was it always like this and I just missed it? If it's not a bug and has to render like this could the log send a warning if it sees refraction inside a 2Sided mtl without thin-walled checked?

    Thanks,
    Attached Files
    www.dpict3d.com - "That's a very nice rendering, Dave. I think you've improved a great deal." - HAL9000... At least I have one fan.

  • #2
    We are aware of the issue (internal bug-tracker id: VMAX-2578 ). I'm not sure if it's a bug or something else. I'll do some asking and write back.
    Last edited by hermit.crab; 07-03-2023, 02:44 AM.
    Aleksandar Hadzhiev | chaos.com
    Chaos Support Representative | contact us

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    • #3
      After further discussion, the correct workflow is to use Thin-walled when using such materials. Otherwise, plugging refractive materials in VRay2Sided is a bit senseless, since it conflicts with the VRay2SIded's translucency.
      Aleksandar Hadzhiev | chaos.com
      Chaos Support Representative | contact us

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      • #4
        Right, that's what I assumed as well, still weird that it shows up in reflection. However, since the 2sided material predates the thin walled checkbox didn't this use to work just fine without it? I seem to remember the old 2 sided material help file examples even having this on the glowing pyramids.

        Not a big deal really (how often could this show up?) Just something I'll have to keep an eye out for. Thx.
        www.dpict3d.com - "That's a very nice rendering, Dave. I think you've improved a great deal." - HAL9000... At least I have one fan.

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