Thin walled OFF has no effect on the Sclera of Genesis 8 female.
Flortale
Posts: 611
Open up Genesis 8 Female. Zoom in on her eyes. Go to the Sclera surface material. You'll notice Thin Walled is off. Try cranking up the SSS and other various settings and do some renders with IRAY. You'll notice they have absoultely no effect. I tried an SSS strength of 20, but nothing changed. I set thin walled to ON and still, no visible changes. Anyone know why? It seems the best way to adjust SSS strength on the Sclera is with Translucency, not Thin Walled off settings. Can anyone confirm?
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If a surface is set to "Thin Walled" on, then the subsurface settings (including translucency) are not available. It also can have odd effects on transparency and such. Subsurface Scattering calculations are a combination of several values. Just increasing the strength may not be enough, transmitted distance, colors, etc. can also have a significant effect.
You could also be seeing something where the glossy and base surface settings are strong enough that they are contributing more to the final look of the surface than anything you would do with subsurface settings. The fact that translucency (which adjusts the balance between the surface and subsurface contributions) has a noticeable effect for the test you were running reinforces this idea.
TL;DR SSS is dependent on the angle and strength of your lights as well as its depth setting, translucency is not.
You can't see an effect of SSS if there's not light shining through something at an angle different from your viewing angle (SSS stands for subsurface scattering, light being scattered when it passes through a surface). You'd have to translate the eyeball out to one side of the figure and shine a light on it from behind or at an angle to really see an SSS even as high as 20 with a low translucency on the sclera of an eyeball. This is doubly true if you left the camera headlamp on, because there's always a bright direct light from exactly your viewing angle if you do that.
Additionally, you can turn the SSS up as high as you want, and if it's set to 2 but the eyeball is not 2 Daz units long (it's much smaller) you're not going to see a change in effect. You want the depth setting to be ideally just below the surface of any object, which is why it's probably around 0.1 by default on the sclera; but if you turn the SSS way up without changing that to 0.008 or something it's probably not going to make a huge difference. This is even more true of the transmission settings.
Translucency, on the other hand, is visible at any angle and in most lighting, so you're going to see more of an effect from it in the situation you're using.
Using a cutout opacity map flat deactivates the thin walled off option in-engine no matter what your settings say, which is a major pain trying to work with any non-geograft creature bits, but that's clearly not what's happening if it's the sclera you're looking at.
Additional note on transmission: this is why the same water shader can look thin and watery blue on a large object but really DARK blue on a small object. A transmission setting of say 5 means that the maximum amount of light is transmitted at 5 units into the object's surface, meaning that's when it achieves the color you set as transmission color. If the object is smaller than 5 units, it's going to look almost black because maximum transmission is achieved at a depth deeper than the object even has. If the object is bigger than 10 units, there's continued dilution through its volume. It's absolute, it is not relative.
One of the frustrating things about Iray is working out which things in it actually ARE physically based, that is to say absolute and therefore varying by scale and other scene factors, and which things are relative and do not vary by those things (like translucency).
Thin walled off setting is broken. The settings do absoultely nothing.
Does DAZ know that thin walled is currently broken? I have multiple lights all around my object. No matter what settings I use
The following settings are broken:
Transmission
Transmitted Measurement Distance - This is the distance light must pass through an object before getting the transmitted color.
Transmitted Color - This property sets the color of the transmission.
Scattering
Scattering Measurement Distance - This is the distance light must pass through an object before getting the SSS Amount.
SSS Amount - This property sets how much scattering is occurring.
SSS Direction - This property is used to determines whether the surface scatters toward or backwards from the light. 0 is Isometric, or almost no scattering - like water. Negative numbers (-) backscatter to the direction of the light source. Positive numbers (+) forward scatter away from the direction of the light.
The following settings are broken. No matter what settings you put, there is no visual difference. Does DAZ know about this?
Thin Walled - This property sets the volumetric effects of the surface. Compare a bubble (on) to a marble (off) for example.
On - When the property is on, the surface takes on the characteristics of a thin walled surface.
Off - When this property is off, the surface takes on the characteristics of a thicker or solid surface item. Thin Walled must be off to get volumetric effects such as Sub Surface Scattering.
Transmission
Transmitted Measurement Distance - This is the distance light must pass through an object before getting the transmitted color.
Transmitted Color - This property sets the color of the transmission.
Scattering
Scattering Measurement Distance - This is the distance light must pass through an object before getting the SSS Amount.
SSS Amount - This property sets how much scattering is occurring.
SSS Direction - This property is used to determines whether the surface scatters toward or backwards from the light. 0 is Isometric, or almost no scattering - like water. Negative numbers (-) backscatter to the direction of the light source. Positive numbers (+) forward scatter away from the direction of the light.
The above settings do absoultely nothing.
If you aren't seeing anything then you aren't using them correctly. I have used SSS in a few renders and, although it takes a bit of tinkering, I do eventually get them to work as intended
Daz's tutorial video on The Iray Uber Base Shader has some good examples and explanations of what the various settings do and what they represent in real world materials.
Thanks. This is exactly what I was looking for.
So it does work.
The setting has to be around .10 ... Now it's working! lol