subsurface

laverdet_943f1f7da1

Hello!!!
I have a question, with sss: I never clearly undrstand how to enhance a skin shader with sss; I mean, if I add Sub surface scatter, with, say, a dark redish Brown, it seems that I have added overall a small amount of glow, with a reddish tone...
anybody experiment that?

Dartanbeck

This is what I posted fore someone else, too.

One of the best explanations of all time is included in a Free Product: Indigone's V4 Skin Shader Kit and Lights, which includes an amazing tutorial, beautiful generic skin shaders that work for any figure period... not just V4 or even Daz Figures, for that matter. Anything. And then she includes a light rig that she spent a long time to perfect for deep shadows. Really worth getting an account at ShareCG if you haven't got one yet. If you follow my lead and get that kit (which I suggest to everyone who owns Carrara), you should also pick up her Endless Eyes Kit Again, she says it's for V4 - but there aren't any figure-specific maps in either pack. They work beautifully on Genesis, Predatron's Troglodytes and Low res people....

It's quite the in-depth topic.
If you have the Native Content installed, they have an excellent example of sss in there - it's a candle.

JonnyRay

Basic concept of (SubSurface Scattering) SSS ... not all of the light reflected by skin (and a few other surfaces) is actually reflected by the top layer. Some light passes through the top layer and reflects off a layer underneath (the subsurface). Further, this subsurface reflection isn't perfect, it deflects (scatters) slightly. The easiest way to see SSS in action is to put your fingers over a lit flashlight ... see the red glow & outline of the bones? That's because part of the light is passing through and being bounced around inside your skin.

Now, the problem (as you've seen) with just applying a simple color to the SSS layer on skin is that your skin isn't universally translucent/reflective. The best way is to have a separate map that controls the strength (and sometimes color) of the effect. I even read an article once by a true master of 3D skin who used three layers of mats (epidermis, dermis, vascular) to get the most realism.

Indigone's shader is a very nice one. I've used it to some good success. She also does a nice job explaining the process. The best would be if the skin / character you're using had one provided, but that is extremely rare.

Dartanbeck

Ooops... Hi Johnny! We posted at around the same time. I'll read what you wrote. I just copied from the text book! lol :-P
From the Carrara 7 Manual, page 575,6

Subsurface scattering is the light that scatters through the volume of translucent materials. It is most visible in semi-opaque materials such as marble, milk, wax, skin, etc. It is characterized by a very smooth and diffuse lighting that filters through the material.

Here is a quick description of the parameters used for subsurface scattering:
•Intensity is the intensity of the effect.
•Translucency is the most important parameter of the subsurface scattering shader. It represents the depth to which the light diffuses into the material. The higher the translucency value, the deeper the light penetrates into the material.
•Diffuse Reflection controls the intensity of the scattering at the surface.
•Refraction Index controls the index of refraction of the material (it has some impact on the scattering intensity) that is used for the subsurface scattering calculations.
•Fresnel Effect controls how the subsurface scattering and the rest of the lighting is mixed. 100% is the most physically realistic. In that case, when the surface is facing the observer, the light is 96% of subsurface scattering and 4% of light reflected from the surface. When the surface is seen from the side it is the contrary. When the the slider is at 0, the subsurface scattering is simply added to the light reflected by the surface.

NOTE! Subsurface scattering varies depending on the size of the objects to which it is applied. The shader works in a way that a given shader will simulate the same material properties for all the objects it is applied to. However, if you want to get the same effect at a bigger scale, you will need to increase the translucency.

Dartanbeck

JonnyRay said:

Now, the problem (as you've seen) with just applying a simple color to the SSS layer on skin is that your skin isn't universally translucent/reflective. The best way is to have a separate map that controls the strength (and sometimes color) of the effect. I even read an article once by a true master of 3D skin who used three layers of mats (epidermis, dermis, vascular) to get the most realism.

I agree, but we can't apply a map in the SSS channel in Carrara, I think. So if I'm making sense from the concept, We could apply the map in the translucency channel? Okay... I have to open Carrara.

In the other thread, she's using the Homo Erectus character, when I noticed that Mec4D actually included SSS maps with the product! So now I need to figure out where those would best be placed within the Carrara Shader...

evilproducer

Dartanbeck said:

JonnyRay said:

Now, the problem (as you've seen) with just applying a simple color to the SSS layer on skin is that your skin isn't universally translucent/reflective. The best way is to have a separate map that controls the strength (and sometimes color) of the effect. I even read an article once by a true master of 3D skin who used three layers of mats (epidermis, dermis, vascular) to get the most realism.

I agree, but we can't apply a map in the SSS channel in Carrara, I think. So if I'm making sense from the concept, We could apply the map in the translucency channel? Okay... I have to open Carrara.

In the other thread, she's using the Homo Erectus character, when I noticed that Mec4D actually included SSS maps with the product! So now I need to figure out where those would best be placed within the Carrara Shader...

I fake SSS many times using the color map in the glow channel. I usually dial the brightness to around 10%. It's very quick. I'll have to try the SSS map in the glow channel to see how it works.

To the OP: Carrara's native content comes with some hi-res skin shaders for V4 and M4. They're under Skin in the Shader Browser. The shaders with SSS have the file name, followed by GI. To see the full file name, hover you mouse over the shader's icon. To use them, select the model under the figure's hierarchy in the instances tab, select the shading tab at the top of the screen and then drag and drop the shader icon onto the multi-colored ball at the top of the screen.

Since the SSS channel doesn't accept maps, you could look at the shader settings included in Carrara and adapt them to your own custom shaders.

Dartanbeck

evilproducer said:

I fake SSS many times using the color map in the glow channel. I usually dial the brightness to around 10%. It's very quick. I'll have to try the SSS map in the glow channel to see how it works.Best idea I've heard all day! Wow!

To the OP: Carrara's native content comes with some hi-res skin shaders for V4 and M4. They're under Skin in the Shader Browser. The shaders with SSS have the file name, followed by GI. To see the full file name, hover you mouse over the shader's icon. To use them, select the model under the figure's hierarchy in the instances tab, select the shading tab at the top of the screen and then drag and drop the shader icon onto the multi-colored ball at the top of the screen.

Since the SSS channel doesn't accept maps, you could look at the shader settings included in Carrara and adapt them to your own custom shaders.

Forgot about those... Yeah.

So here is an example of how subtle a difference sss can make without going through any special trouble.
Before reading EP's advice regarding the Glow channel - Man, that's a great idea for sss maps - I was looking at various ideas for them. You see, once you turn on Subsurface Scattering in the shader, I believe that others have confirmed that it does take control of translucency, refraction and such. It appears that Indigone uses the Highlight values with a waves modifier in the highlight channel to help control it. I'm using a supplied Specular map, but instead of my normally lower value, I'm running it at 15%, which is where Indigone had hers set.
I am using Scene - Background - Bi Gradient With white at the top, horizon maxed, for a light dome so I used a Bi Gradient in Backdrop to keep the actual background of the image from blinding us. I turned on Global Illumination, but no indirect lighting of any kind. I also have my default accent lights that I keep with this model, although the rig often needs to be tweaked or removed per individual scene needs.

Dartanbeck

celmar said:

Hello!!!
I have a question, with sss: I never clearly undrstand how to enhance a skin shader with sss; I mean, if I add Sub surface scatter, with, say, a dark redish Brown, it seems that I have added overall a small amount of glow, with a reddish tone...
anybody experiment that?

True... it IS very subtle

Edit: I updated the above post that was lacking some important notes.

Another edit:
With the ability to see both images together in this thread, if I had to choose between them, I hands down, prefer the Subsurface Scattered image. It actually absorbs enough of the light and scatters it to remove the darkness that the shadows create without it.

evilproducer

It's kind of cheeky, but for this A3 scene I copied and pasted the image map from the color channel into the glow channel. I used the brightness slider under the image map thumbnail and adjusted it down to 10% brightness. The irises and whites of the eye I set to 15%. The scene has one light, a white color in the scene's backdrop and in the render room I enabled the Skylight, which treats the background color as a light source. It rendered very fast. I still have the scene, so maybe I will run a test tomorrow with SSS to see the difference.

This is the image straight out of Carrara with no postwork except to resize and convert to a forum friendly format. No levels adjustments, etc.

Kevin Sanderson

Check this thread over at Rendo and look for the posts from jt411 and his examples in Carrara using the Multi Channel Mixer and a gray scale map for the blender. Renders faster. Pretty neat!

http://www.renderosity.com/mod/forumpro/showthread.php?thread_id=2859803

Dartanbeck

evilproducer said:

The scene has one light, a white color in the scene's backdrop and in the render room I enabled the Skylight, which treats the background color as a light source.

Right. That's the technique I mention above. Background (not backdrop) Bi Gradient and leave it as it is, except change the top box to white and crank the horizon to 90. This leaves the Backdrop to use as anything... without effecting the light from the background. Cool trick I picked up from Cripeman's Global Illumination tutorial ;)

Dartanbeck

Kevin Sanderson said:

Check this thread over at Rendo and look for the posts from jt411 and his examples in Carrara using the Multi Channel Mixer and a gray scale map for the blender. Renders faster. Pretty neat!

http://www.renderosity.com/mod/forumpro/showthread.php?thread_id=2859803

Drats. I don't have login on this computer. No chance of reproducing it here?

evilproducer

Kevin Sanderson said:

Check this thread over at Rendo and look for the posts from jt411 and his examples in Carrara using the Multi Channel Mixer and a gray scale map for the blender. Renders faster. Pretty neat!

http://www.renderosity.com/mod/forumpro/showthread.php?thread_id=2859803

I have heard of this method before, I just hadn't seen it implemented or any examples. Thanks for the link, Kevin. His examples look pretty impressive!