What problem is being displayed in this shader? What phenomenon is causing this waffle-patterning in this transparent texture? I want to research what is happening, but don't know what direction to go.

Originally, I started off using a principled shader, but even the plain sss shader is exhibiting this.

Can I add a blend file to these questions? 





Here's the blend file:


this was the pbr shader, with the Christensen-Burley surface method. It took a long time to render, compared to the random walk one with the plain SSS


Plain SSS


I added the level 1 modifier, but these artifacts are still visible


Here's the node tree that I ended up going with, after taking the subdivision modifier back off of the mesh. The influences of the SSS in the shader seem to be negligible, and I'm happy with the result-- wasn't going for physical accuracy.

Hopefully, this helps someone out there
I believe it's the fact that the resolution of the mesh is so low that the angles from face to face are so sharp that the SSS sees it as a corner that is thinner and thus lightens it up (expected from SSS, but rather extreme). The sharper the corner the brighter. As soon as i added a lvl 1 subsurface modifier, it made the surface smooth enough geometry wise to calculate the surface as if it was one rounded shape.

The fact that if you change the shading to Flat Shading the brighter lines along the sharp folds of the faces becomes even more pronounced makes me sure that SSS really only gives that result because on the low resolution surface.

Here a comparison with a quadsphere with just one point dragged out to create an extreme that the SSS instantly shades as it did in the file shared.

Also visible here is that the quads seem to be internally triangulated and the resulting edges are generating the thinner corners or folds which get calculated by the SSS algorithm. Specifically the "Volumetric" version used in Random Walk as that is a volumetric approximation of a physically based volume scattering.

While it was not asked for a solution, i would still think that a level 1 subdivision modifier should get rid of the pattern.



This result i got from rendering with 128 samples at full resulution and only lvl 1 subdivision surface modifier. I had to remove the background and replace with a color, as the image was missing. Also due to the camera setup being a bit stubborn, i deleted it and created a new one for a simple close up. If you did not use anything on the camera.



This is with the adjusted Principled BSDF shader.