Why Won't the SSS Radius Socket Take Input Values Properly?


(Kevin McKraken) #1

In either the Principled shader or SSS shader, there is a value that seems to take in RGB values that you input and uses them to change the size and color of the scattering, called “Radius”. This value appears like it would be far easier to control if you were simply able to select a color through the color picker, then adjust the size/distance of the scatter separately. However, even though there is an input socket available, it doesn’t really like it when you plug something in.

So, my question to you comes in two parts:

  1. Is there a way to control the Radius values as stated?
  2. If there is no way to control it externally, why have an input socket in the first place?

My current progress:


As you can see, the size can be increased this way, just not the color. No matter what I set the color to, it doesn’t change. Also, this only works with the Principled shader, the SSS shader won’t be effected at all. I’m completely willing to accept that I have no idea what I’m doing.

Any help would be great!


(pixelgrip) #2

with a quick look at your nodes,your sss scatter multiplyer group seems right to me.i have used often similar math like this.

you must keep in mind two things with sss.first the object scale and the radius are both in blender units.
and second.the sss afaik is based on volumetric distance radius.

try out susanne as object with random walk.look at the dimensions the object has.now scale/multiply your radius to the proportion (object size) the object has (mostly smaller than the object size).
if your radius is way bigger as the object,then your radius gets out of the object, if that makes sence.

and not to forget if you scale your object,that you need to apply the scale with CTRL+a


(CarlG) #3

Trying eevee on non gpu laptop running linux (first time since, ever), I can’t get the blue radius inputs to accept any yellow color input (with or without separatergb->combinexyz node, which I don’t think should matter anyway). Adjusting the radius directly works.

Tested with default subsurface node, not principled.


(Kevin McKraken) #4

I’m having no issues adjusting the radius as a scatter size, but only as an actual RGB color. I’m only trying to avoid having to manually adjust the radius values for every material I create, they won’t all have a red scatter. I find using a color picker and multiplier would be an easier solution for me, but it seems like splitting the RGB values and changing them to XYZ just doesn’t work for this.

As you can see, when I change from a pink color to a green color, the scatter color doesn’t actually change.


Even when I set it to this solid blue, which should have a radius value like, (0.0, 0.0, 1.0) * 0.2
It stays red.

In theory, it should work this way RGB (0.0, 0.0, 1.0)*0.6:

I am aware that the node is disconnected, it had to be for the example.


(Kevin McKraken) #5

After further investigation, I discovered that this problem is with Eevee. After testing with Cycles, it seems the issue is sorted out. Still doesn’t work with Eevee, but hopefully in the future!



(pixelgrip) #6

yes in cycles it should work.i have not tested with Eevee much.maybe some checkbox need to be activated for the Eevee engine?
have seen some glass shader videos,for Eevee, there you need to activate screen space reflection + refraction ect ,to get some proper glass shader.maybe here is missing a checkbox too.


(Kevin McKraken) #7

I have all required settings enabled. I posted a bug report to the developers, hopefully they can see what is going on.


(CarlG) #8

Have you checked against the Eevee compatibility “thing” (I’m on a lousy computer so I won’t spend time finding it for you :stuck_out_tongue: )? Not everything is supported by Eevee, maybe it is hardcoded?


(Kevin McKraken) #9

Well, they were nice enough to give a link to the limitations page when they closed my bug report. So, I guess this is the case. Now I can only hope that it’s resolved soon, if ever.


(pixelgrip) #10

just have seen this video.have not checked the radius,but here we can see the basic checkboxes need for backlit translucent sss ect.


(Kevin McKraken) #11

I appreciate it, but I have stated that I have no issues with getting the basic effects to work. Discovering that my issue stems from a limitation with Eevee, I am no longer looking for answers to this topic.