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

[dlparisi]

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:

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, . 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,

2Sided Test.zip (78.3 KB)

[hermit.crab]

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.

[hermit.crab]

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.

[dlparisi]

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.