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Luxus Skin Settings
Posted: 21 April 2013 06:01 AM   [ Ignore ]   [ # 31 ]
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vwrangler - 21 April 2013 04:56 AM
InaneGlory - 20 April 2013 05:20 PM

Glossy Translucent Absorption Color and Volume Absorption Color shouldn’t be the same exact color. The first one is for light bouncing off the skin, the second for light penetrating the skin.

OK, now I’m very confused. If those colors aren’t supposed to be the same, then how do you know what should be what?

According to the information at the Luxrender wiki:

(Volumes) Absorption color: ... The absorption color determines how light is lost as it passes through the volume. This defines an attenuation rate, meaning that the color will be become more dark and saturated the farther it travels through the volume. It also means that this color control will seem to work “backwards”. If you specify the raw absorption color as red, it will remove red light, leaving you with a cyan volume….

(Glossy Translucent) Absorption Color/Depth: ... These allow you to specify the color and depth of light absorbtion by the surface coating. Note that since this is an absorption color, it will seem to work “backwards”. Setting it to blue will cause blue light to be absorbed, leaving you with a yellow-orange appearance. To defeat this option, set the color to full black (0.0). This parameter is not related to volume absorption….

According to that explanation, although they very technically do different things—reflected versus absorbed/passed-through light, although both address it in terms of what gets absorbed—they seem to require the same settings.

I know this is not technically correct, but thinking of it this way helps me visualize what I am trying to do with these settings.  “This one has to be set high and this one low, this one is dark and that one is light.”  But as I picture it, this is the way it works.  Volume is like your muscles beneath your skin.  Setting a higher volume scale is like setting the power of your muscle tissue to shine its way through your skin, like when you put a flashlight behind your hand and you can see it shine through.  The stronger the flashlight, the more you will see it.  So choose a color and strength that will show through the skin (the glossy-translucent settings), but still look natural Don’t choose a red color like your actual muscles, but instead choose something more like a darker version of your actual skin color.  And don’t forget to enter it as a reversed color.  Red reversed is cyan, Green reversed is magenta, and Blue reversed is yellow.  So Caucasian flesh color, which is orangey-pink (red and yellow and white), which reversed would be cyan and blue and black.  That means a darker cyan-blue makes a pale peach.  I know the documentation says the parameters are not related, but you can definitely see a correlation between the glossy-translucent absorption and volume absorption whenever you change either setting. 

The glossy translucent absorption (GTA) parameters are like your actual skin.  They represent a coating around the volume.  The lower the strength of the GTA, the more of the volume effects will show through.  Likewise, if your volume settings are too low, you will end up with a pale, washed out skin.  So choose a GTA that approximates the actual color of skin you want and don’t forget to enter the RGB values as opposites of the RGB values of your actual chosen color.  As for the GTA scale, smaller values will appear as paler versions of your GTA color because the “skin” is thinner, therefore reflecting more light than it absorbs.  Thicker scales will absorb some of the light, bringing out the more true value of the chosen color, while at the same time reflecting light back out through the skin giving it that waxy, translucent look.  Find a balance between thickness (scale) and color or you will end up with white tips on the end of the nose and the ears! wink  I think of the scale settings in terms of centimeters, though that is not technically correct.  Human skin is, at it’s thickest, about 4mm or nearly 1/2 centimeter thick.  So, keep this setting in the .3 - .5 range.  A little higher if you are going for an effect.

As for scatter, the scale should be similar to, but not necessarily the same as, volume absorption scale for the same reasons.  You want the scattering effect to be visible through the GTA, but not overwhelm it.  Here is where I would choose a color with more red in it, since the blood vessels under your skin are flowing with red blood, which contributes to the color of the light scattered under your skin.  That said, don’t make it literally red because the tissues in your skin are also contributing to the light color being scattered.  I like to choose a reddish brown.  This way, you get the redness from the blood, but also the brown of the melanin in our skin.  Too much red and you have a sunburned Vicky!  If your character is particularly pale, such as a vampire or albino, then you can go for a bluer tone, more likely purple or lavender so that some red is still present.  This color does not have to be reversed.  It is a direct color because there is no absorption involved.  I think of the scale for volume in millimeters (cm for skin, mm for volume).  My body is about 17” wide viewed from the front, which is 430 mm.  So, I set my volume around there.  Guys like the Freak are big, so I went to 500 for him.  Females and kids might be around 10” to 14” wide, so 250 to 350 is a good place to start for them.

Again, nothing scientific about most of what I wrote here, it just helps me to think in these terms and seems to work.  A few of the stats I listed actually are scientific (at least according to Wikipedia) like skin thickness, etc.  These are good starting off points for you, at least.  Also note that human skin has an index of refraction (IOR) of 1.45, so set your volume and specularity IOR’s to 1.45.

I hope my theories help someone.  I am very sleepy right now and may have rambled a bit and for that, I apologize.  Also, thank goodness for spell check, because sleepy people should not be allowed to type.

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Posted: 21 April 2013 08:16 AM   [ Ignore ]   [ # 32 ]
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Slosh - 21 April 2013 02:33 AM

I re-rendered the previous image with InaneGlory’s settings, but tweaked them with the suggestions I gave.  Here are the actual values I changed and the reasons for it.

LuxRender Glossy Translucent - Diffuse Color: 255-255-255 (Diffuse Map)
(I changed to 225:225:225)
LuxRender Glossy Translucent - Transmission Color: 255-255-255
LuxRender Glossy Translucent - Specular Color: 143-176-186 (Specular Map)
LuxRender Glossy Translucent - Specular IOR: 1.4
(changed to 1.45, more accurate for skin)
LuxRender Glossy Translucent - Specular Roughness U: 0.8
(changed to 0.4, to make shinier)
LuxRender Glossy Translucent - Specular Roughness V: 0.8
(changed to 0.4, to make shinier)
LuxRender Glossy Translucent - Absorption Color: 0-0-0
(changed to 0:50:71 for fleshier color.  Yours was actually orange)
LuxRender Glossy Translucent - Absorption Depth: 0
(changed to 0.38)
LuxRender Glossy Translucent - Multibounce: On
LuxRender Glossy Translucent - One Sided: On
LuxRender Volume Type: Homogenous
LuxRender Volume - Refractive Index: 1.3
(changed to 1.45 for human skin)
LuxRender Volume - Absorption Color: 23-123-255
(changed to 23:94:122, a fleshier color)
LuxRender Volume - Absorption Scale: 2250
(left the same)
LuxRender Volume - Scattering Color: 64-52-45
(changed to 128:64:0, which is redder, but still brown)
LuxRender Volume - Scattering Scale: 4
(changed to 100 to penetrate deeper into the large volume of 2250)
LuxRender Mesh - Bumpmap: 1 (Bump Map)
(changed to .002, Lux overdoes the transferred bump)

I feel a little odd about offering suggestions now, since it seems obvious that what clearly works for me, clearly does not work for ANYONE else.  I don’t know what to say.  Maybe we can all discover it here, together.  I will have to rethink my suggestions.

I don’t suppose anyone else who has posted here would like to send me their scene file, so I can see what their settings look like on my pc?  I have all of the Gen5 figures and most of the textures that came with the bundles.  I truly hope someone will take me up on it.  I will give you my personal email address if you PM me and you can send me your scene files.

I like it I like it a lot. I’d love to see a more finished version. I think the skin tone is much more realistic now. Like I said I wasn’t very happy with my results but I like what you’ve done with it. Most of the range of data I used came straight from .lxs scene files that was auto-converted from UbS2. Not saying one set of data is right and the other is wrong, just stating where I got the info from.

Info I’ve found on the web on the IOR of human skin varies depending on who did the test. Range seems to be between 1.36 and 1.44 in the sources I’ve seen. Guessing that in the real world the value does vary between different people.

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Posted: 21 April 2013 08:28 AM   [ Ignore ]   [ # 33 ]
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Are you going to make adjustments to your image similar to the ones I suggested and re-render?  Or are you putting this one on the back burner for now?

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Posted: 21 April 2013 11:30 AM   [ Ignore ]   [ # 34 ]
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Its very generous of you to share the scene.
Weird thing is, its working now. I can’t issolate what is the difference between my scene with your settings and your sharecg scene. They totally look the same.

Its rendeing slightly yellow, but making minor adjustments looks fine.
I’ll try some more things to see if I came up with what’s happening.

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Posted: 21 April 2013 11:38 AM   [ Ignore ]   [ # 35 ]
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This is after 1 hour 25 minutes
Made some minor adjustments to the color space and set Areal Light.Default to 2 to make it closer to yours.
Now, off to see whats going on.

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Posted: 21 April 2013 01:07 PM   [ Ignore ]   [ # 36 ]
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Slosh - 21 April 2013 01:41 AM

This is just crazy!  I can’t understand how NO ONE has been able to duplicate my results.

I don’t know, I thought what I got was pretty similar. I’m glad to see Hellboy’s is working now too. I’ll download the scene file just to compare though.

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Posted: 21 April 2013 01:11 PM   [ Ignore ]   [ # 37 ]
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♫I’m SO posting this on Deviant as miiiine♪
(Not true)

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Posted: 21 April 2013 02:16 PM   [ Ignore ]   [ # 38 ]
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Hellboy - 21 April 2013 01:11 PM

♫I’m SO posting this on Deviant as miiiine♪
(Not true)

Ha ha!  LOL

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Posted: 21 April 2013 02:18 PM   [ Ignore ]   [ # 39 ]
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Agent_Unawares - 21 April 2013 01:07 PM
Slosh - 21 April 2013 01:41 AM

This is just crazy!  I can’t understand how NO ONE has been able to duplicate my results.

I don’t know, I thought what I got was pretty similar. I’m glad to see Hellboy’s is working now too. I’ll download the scene file just to compare though.

Yeah, yours was the closest match, but still looked “burnt”.  I hope we can figure out what the difference has been and if Hellboy can repeat it on one of his characters, we may be able to solve it.

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Posted: 21 April 2013 02:58 PM   [ Ignore ]   [ # 40 ]
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Slosh - 21 April 2013 02:18 PM
Agent_Unawares - 21 April 2013 01:07 PM
Slosh - 21 April 2013 01:41 AM

This is just crazy!  I can’t understand how NO ONE has been able to duplicate my results.

I don’t know, I thought what I got was pretty similar. I’m glad to see Hellboy’s is working now too. I’ll download the scene file just to compare though.

Yeah, yours was the closest match, but still looked “burnt”.  I hope we can figure out what the difference has been and if Hellboy can repeat it on one of his characters, we may be able to solve it.

That’s just because my guy was crouched lower, away from the lights, and I didn’t adjust them. The test scene renders perfectly.

I’m loving the lowdiscrepancy sampler. Such an improvement on render times.

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Posted: 21 April 2013 03:01 PM   [ Ignore ]   [ # 41 ]
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Actually, mine is redder there. It may be down to what Daylight you’re using. This looks a bit closer to the color. I suspect the difference is just gamma or other color space settings. Plus I haven’t run mine long at all.

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Posted: 21 April 2013 04:49 PM   [ Ignore ]   [ # 42 ]
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Maybe someone knows the answer to this…
I’m trying the settings on Sol Elite, lowered the absortion and scattering scale to 1 and Sol’s specular maps are darker, so I made the specular color lighter, however I see no difference, I’m using white now, which usually would give me am unusuable highlight, but the skin still looks almost matte and very warm. And the skin is granulated and taking more to render, as it happens with very shiny materials.
Someone knows what could be happening?

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Posted: 21 April 2013 07:32 PM   [ Ignore ]   [ # 43 ]
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Hellboy - 21 April 2013 04:49 PM

Maybe someone knows the answer to this…
I’m trying the settings on Sol Elite, lowered the absortion and scattering scale to 1 and Sol’s specular maps are darker, so I made the specular color lighter, however I see no difference, I’m using white now, which usually would give me am unusuable highlight, but the skin still looks almost matte and very warm. And the skin is granulated and taking more to render, as it happens with very shiny materials.
Someone knows what could be happening?

For the specularity issue, if you are using IOR on spec channel, changing the spec color will not make any difference.  The IOR automatically sets the spec color to mid-gray.  Either lighten the spec maps in another program or remove the IOR.

I also tried this with Elite Sol (one of my favorite textures).  I wouldn’t lower the absorption and scattering scales to such a low number.  Nothing under 100, really.  If his skin is looking too saturated with these settings, try lowering the glossy-translucent absorption scale.  I think the Freak file is set to 1, but realistically you want between .4 and .65 or so.  Also, because his texture is already a bit more saturated, you might try desaturating the glossy trans absorption color, or lightening it.  Easiest way to do this is to lower the “S” slider for saturation or the “B” slider for brightness in the HSB section of the color picker.  Remember for making absorption colors brighter or darker, you do the opposite to your entered color, so lighter tan equals darker blue, etc.  Let me know if this helps!

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Posted: 21 April 2013 07:36 PM   [ Ignore ]   [ # 44 ]
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It seems to me that I must have been using some setting on my computer that I forgot to tell the rest of you about.  Not sure what it could be, but apparently when you opened my scene on your computer, it flipped that switch.  I am happy to know it, but would really like to figure out exactly what it was so I can include the instruction in future tutorials.  As soon as I have ironed out all of the details and can start a scene from scratch and know almost exactly what I need to do to set the skin, I will be writing an in-depth tutorial.

I am so happy to see all of the freaks showing up in this thread.  Now, to see how it applies to your own characters.  Hellboy, I know you like to use Hyde a lot, so I am looking forward to that.  I honestly didn’t even know such a character existed until now.

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Posted: 21 April 2013 09:10 PM   [ Ignore ]   [ # 45 ]
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Could one of you send me a scene file from an earlier render on this thread?  I want to compare it to my settings and see if I can get to the bottom of this.  Please make sure the file was saved prior to having downloaded my scene file.  If my scene file changes a setting in your render settings, I don’t want the file to have been re-saved with the change in it.  Know what I mean, jelly bean?

Thanks!

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