Black artifacts Eye lid fold

[Jonatan Lyssens]

At the point where the eyelid fold ends, it becomes a wrinkle. The texture is turning black, is this something I need in the sculpt, or is this something that will be resolved in the following part of the course? If I should fix it now, any suggestions? 
https://drive.google.com/file/d/12PZHgEKYCEvDRzf3_UvM5_0LXtrv60ho/view?usp=sharing

[Omar Domenech]

Maybe check to see if those are back faces and that’s why it’s giving you that black area? Turn on face orientation and see if it’s red. It’s doesn’t look that bad though, you really have to be in there super up close to even notice it.

[Martin Bergwerf]

Hi Jonatan @JonatanL ,

That could also be because of the Subsurface Scattering.

That seems to be too much in your Image and maybe uses the wrong method (should be Random Walk (Skin) in Blender 4.0+ with a Weight of 1.000 and a low Scale, or just Random Walk (not the Fixed Radius one), in older Versions, with a low Subsurface value). In even older Versions (like 2.9 or so), the SSS methods were slightly different, if I remember correctly, but then they would be like in the Course.

[Jonatan Lyssens]

Hi, 
Thank you for your swift replies, as always. I had some nasty spike multires artifacts around the eye. It took me a while to get those out. I often turn face orientation on to avoid bad normals when I fix those.  I can’t see any red in the sculpt. 

I took over the material that was in the pore depth Blend file. “Random Walk weight: 1 Radius 1-0.4-0.1 Scale 0.150 Anisotropy 0.0

When I reduce the scale to 0.05 there is definitely less of the black. But it’s not gone. Could it be that the subsurf is influenced by the proximity of the fold above it where their are normals that are intersecting. I have tried inflate that fold so it isn’t intersecting that much. But without much success

[Jonatan Lyssens]

Okay. I think I might have found a clue. I went looking for band normals and I looked at that specific area in Edit mode. And I found that in that spot there is a weird topology. That I didn’t spot before. Not sure how I would describe it but it seems one of the faces is twisted in a weird way. Creating what seems from some angles like a face without an edge. I have some Prtscrs here: https://drive.google.com/drive/folders/1JC-7ySveuvtWDAkO9lmGjTbtICpRvZFe?usp=sharing 

It is like if you would number your vertices in order clockwise. 1, 2, 3 and 4. Then 3 and 4 would be in the same plane. But 1 would be higher than 2, making like a fifth ghost edge which isn’t there. So where this twists the subsurface turns black. Not sure if this makes any sense. I hope the prtscrs make more sense. Any idea how I could solve this, preferably without destroying my eyelid? 

[Martin Bergwerf]

Hi Jonatan,

Some remarks:

What you are describing (and showing in your screenshots) are so-called ‘broken Quads’, when the 4 Vertices of a Quad do not lie in a single plane. (This is why Renderers Triangulate everything, because 3 Points (Vertices) always lie in a plane.) They are generally to be avoided, but when you are throwing a ‘Catmull-Clark’ (through a Subdivision Surface, or Multiresolution Modifier) at them, they tend to cause less (or no) problems.

Using the same numbers as in a Tutorial never guarantees and rarely gives the same result.

The eyes (and mouth corners) are difficult areas to get right, because of the folds, Faces being very close together…It’s what causes the spikes and the SSS Shading issues. If you have gotten rid of the spikes, I shouldn’t worry too much about the black Shading artifacts at this moment. Concentrate on the Pore Depth. The SSS Values can be dialed in better, when you have all the Textures ready…if it is still necessary then.

[Jonatan Lyssens]

Thank you for this explanation. So at this point in the process, I leave it as it is. But I will take it with me on my next retopo. It might also explain that I had an issue with the shapekey after shrinkwrapping, the first time. Great insight. Thank you. 

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