OTOY Forums

I'm doing a clear label with opaque printing on a plastic bottle with subsurface scattering and find that mixing any diffuse into the bottle material creates incorrect colouring under the label. Issues occur adding a percentage of diffuse and also using 100% sss with the diffuse transmission option found in the standard surface, a diffuse material layer plus coat layer, or the universal material. The diffuse example here is only diffuse, which shows the strongest effect. Typically, I use 25-50% SSS weighting with the standard surface material. I kinda solved the situation by using a purely specular SSS setup for the bottle, not shown below. .

I've made a simple example scene. Is this the correct result from this mesh and material combination? I've been told it's due to the diffuse being excluded from nested dialectrics, but I don't recall having this sort of result before that feature was introduced. Both Modo and Vray 4 render without issue, neither of which has nested dialectrics.

Sorry, could you share an .orbx scene?

ciao,
Beppe

Oops, I forgot that was a Modo file. Here's the ORBX...

It appears some files are missing and the ORBX is not identically corresponding to the posted preview renders.

Meanwhile an updated ORBX and while it should be possible to match Modo's output In Octane, it's worth pointing out for clarity's sake that neither will precisely match the "flat color swatches square samples" shown due to the effective influence of shading (in the material and lighting sense) and evidently the curved-shape nature of the object accentuating shading (concentric reflections spots, terminator shadow line, and so forth).

Additionally, the "Albedo" (Diffuse Filter) AOV is of a great utility in such cases.

"Trouble solving" questions:
1. is "color management" identical? Presumably the default ("linear to display sRGB")
2. is the lighting mismatched? "HDRI" only?
3. Are "colors" from texture files or native nodes i.e. RGB/Gaussian nodes (in Octane)?

The ORBX was a simplified scene; I've posted examples rendered from that below. But updated the ORBX to have both the diffuse and specular examples.

I've created confusion by posting those initial renders, as they are not generated under the same conditions, hence they have a very different general appearance. Please ignore that. I was speaking specifically about the more saturated area under the clear label shown in the Octane render. Both renders have a 100% specular label intersecting the bottle. In Modo, this combination renders as I would expect, ie the label does not drastically change the bottle colour. However, I did some further research and found that turning on double-sided on the label material in Modo default, and Modo mpath generates a result similar to Octane. Mpath is Modo's newer pathtracing engine and has a double-sided enabled internally, I believe. I also had a good result in Vray 4, except it seems to add the label and bottle reflection together. Of course, now the client has asked for the print directly on the bottle instead, which simplifies things. I've included a sample of that below as well.

However, I'm still interested in learning how to set up the clear label on a diffuse, or diffuse/sss mix material and avoid the problem. Note that I'm not counting using thin material option as a solution, as it removes the opaque printing elements shadowing on the bottle.