[osuire]

Hi Jeremy,

In the following image, I used the membrane material you made me :


Although I applied the material to Nurbs surfaces, the result looks like an unwelded mesh (sort of like flat shade).
Is this a limitation of the new Single Surface SSS ?

Cheers,

--
Olivier

[JDHill]

I suppose so - have you tried using denser meshing parameters? The fact that you make a mental distinction between NURBS and mesh objects leads me to believe that you think there is some difference between using one or the other - there isn't; Maxwell just renders meshes, so you need to mind the meshing params for your NURBS objects, because it's the Rhino render mesh that gets exported.

[osuire]

Hi Jeremy,
I was just pointing out the membrane was a Nurb surface because render meshes of a Nurb are necessarily welded, thus should render smoothly.
I could have had an unwelded mesh, and then the aspect of the render would be justified.
To me, this means there is some improvement to be done on the Single side SSS.
How about cloth or curtains ? This "flat shade" appearance will not yield very realistic results unless insanely dense meshing is used...

--
Olivier

[JDHill]

Yes, I wasn't so much making any claim either way about the engine's behavior with thin SSS vs. mesh topology, but more wondering whether it is in fact taken care of by upping the mesh density. I would suppose that there is refraction to be calculated in your scene, and that the size of your triangles here is large enough that any angular interpolation (if there is any) between faces is insufficient to smooth it out - I am unsure of how this behaves in contrast to the standard normal smoothing that happens with reflectance. So to ask the question directly - does increasing the mesh density in fact take care of the issue? If that is the case then I would guess that you have a very valid request for changing how the engine deals refraction vs. mesh smoothing. That's my guess about what we are seeing in the above image anyway.

[osuire]

Jeremy,

The shape of this membrane is very smooth, and I feel the triangles are reasonably small considering the overall size of the membrane and it's shape.
This is why I pointed out more tricky shapes like drapes and curtains which typically could benefit from this material, but are very curvy, and could look real bad if a proper smoothing is not applied.
I hope this new SSS feature was not designed only for flat leaves

--
Olivier

[kami]

are you using any bump?
this issue occurred (and I think is still occurring) with bump surfaces as well

[JDHill]

Like I say, I am just guessing here because I don't know how it works inside the engine. What Kami is referring to about bump vs. normals smoothing for reflectance is analogous to what I am saying regarding thin sss refraction vs. normals smoothing - I don't know how that is handled internally when it comes to thin sss. I do know that bumped surfaces can produce smooth caustics, so I'd tend to think there is something else going on here. It seems apparent anyway, from looking at your image, that this issue is definitely related to the size of triangle exported. Either way, you'll probably get further with the question by asking it in the Maxwell forum rather than the Rhino plugin forum - the plugin exports the same meshes regardless of what type of material is applied, so I don't quite see how it can be a plugin-related issue.

[Polyxo]

the plugin exports the same meshes regardless of what type of material is applied, so I don't quite see how it can be a plugin-related issue.

Hi Jeremy,
couldn't this be somehow related to the errors when using Global-Bump I sent you some time ago?
Global Bump is still completely unusable from within the Rhino-Plugin... Mesh-Artefacts appear all over.

cheers, Holger

[JDHill]

Anything's possible Holger; like I said though, the plugin doesn't export anything differently based on material (or global bump), so any difference you see when rendering the same mxs files from Studio must necessarily be due to mesh optimizations done by Studio.

[Polyxo]

Anything's possible Holger; like I said though, the plugin doesn't export anything differently based on material (or global bump), so any difference you see when rendering the same mxs files from Studio must necessarily be due to mesh optimizations done by Studio.

Thanks Jeremy,
so I should write McNeel that they should check their Mesh-Smoothing behaviour?
The global-Bump-Error is pretty annoying...

[JDHill]

No - I highly doubt they would be able to do anything to help with your issue, and it may not be anything with normals at all - it looks more to me like some problem with triangle winding order getting screwed up. I think this is something that has to be dealt with on our side - luckily we can see that Studio already knows how to handle it, so whether the remedy is something that ends up baked into the SDK, or if it is code I have to add to the plugin, we'll handle it here.

[Polyxo]

No - I highly doubt they would be able to do anything to help with your issue, and it may not be anything with normals at all - it looks more to me like some problem with triangle winding order getting screwed up. .

Ok. Thanks Jeremy!