subScatter skin with FG problem


#1

On the left, my skin shader with an added tint of Mark Davies subScatter in the incandescent channel, no FG only 2 spotlights (well 4, 2 of them only connected the subScatter node and shadows, spec and diffuse switched off).
On the right, same but with FG switched on (very few rays so it’s low quality). There’s an IBL there, citystreet with some blue sky at the top. Anyone know why the skin with the subScatter reacts by going darker?


#2

Mark Davies subScatter dont like fg try diffusion or do a pass


#3

…aha. Thanks.

edit: But - kryoboy seems to be able to do it, or did I misunderstand (at the top here:)
http://www.cgtalk.com/showthread.php?t=108412&page=49&pp=15
Kryoboy, are you comping that or isn’t it the Mark Davies shader?


#4

I dont think the problem is in fg not working with md_ss.
It looks to me more of a IBL thing.
Here is a simple test with fg and fg off, no ibl.

What are your irradiance settings, do you use a scatter model blend?
Btw, nice shader Steven.


#5

Here’s a test with FG, without an ibl. The brighter it is, the bluer she goes. Same relationship with ibl’s too.

The irradiance and irradiance color are both zero on all the skinshaded surfaces, I found that light was bouncing too strongly between them otherwise. My settings on the subScatter:
Scatter Model Blend 0
Absorption (HSV) 16/1/1
Scattering 93/.4/.6
Extinction 9
RI 3
Anisotropy .65
Fresnel 1
Samples 4/8, Radius 0
HSV diffusion 0
I’m going to try some Scatter Model Blend now, with darker Absorption, redder scattering and some other tweaks.


#6

Render SSS as serpeate pass. You will have more control that way.


#7

Here are my quick settings for working fg:

Scatter Model Blend: around 0,4
Irradiance color black and irradiance about 0.25
Other settings are pretty much the same except some
lower numbers for absorption and scatter color.

Well, when I look at it little longer, there is one
major difference, I used refraction index little above 1, your is 3.
Scattering effect gets more pronunciated with high RI,
and it looks very nice but I get lots of grain and couple of
strange rays around nose and lip (that little veins are ss shader,
not me painting, I dont want them).
Sampling is 32 / 64.


Maybe is raytracing shadows I’m using?
I’m still having a bit of oversaturation problem here,
even with low saturated absorption and scatter color, no
saturation in lights, any ideas?


#8

Really cool, you know that looks almost exactly like rendered by an illustrator? It looks like a certain style of brushwork, often used in illustration.
Yes, the settings you mentioned are closer to what I have now, after another full day of testing.

Anyway, I found part of the problem, it’s the cartoon-shader I used in the Color channel - actually in the Color Gain of the texture in the Color channel. The top part of the ramp is blue, that’s where the blue tint came from. FG seems to react that way to such a ramp whether or not the subScatter node is used. I tuned it and it’s okay.
But now I can see other artifacts when I try to render the scene all in one, artifacts caused only by the spotlights connected to the subScatter node. So I have to do it in 2 passes, as has been suggested. Unless someone knows of a way to ‘disconnect’ lights from a specific Maya shader, like the mr nodes light list works (not geometry, and not the whole Shading Group)?
This is what I have so far, 2 spotlights, FG, no ibl. I think I need the Dirtmap to darken some tight corners.


#9

An update, with added Dirtmap. FG also needed to have a large min and max radius, and when I set the filter to 0 it improved a lot.


#10

Do you have anything else but the shader network on there, as in painted maps?


#11

Yes; a colormap, except on the lips. A spec map. And an ambient map, to make the sss fake a bit stronger on and around the nose/nostrils. No bump map though, it’s a complex animated network I’m having some speed issues with right now, and I need to fix it.


#12

I do have a color map, very faint one and desaturated,
giving the subscatter shader more room.
Bump map, rough one is also there, incadescence with
some incidence control, blue rim.
Top layer is for lips. I used only this two layers
as layer textures for speed issues I was having with
more fancy connections.
This the last test I like somehow more, little more balanced.

Here is lower refraction index, about 1.2
Those strange veins were little flows in my topology.
I’ll have to fix that and use high RI again, yipee.
One thing is that RI between 2 - 3 renders considerably
slower then RI little above 1.


#13

stahlberg, your non-raytraced skin shader looked amazing. any particular reason for going the more time-consuming route?


#14

i-d, that’s looking better there. Thanks for the tip on RI.

Thanks wedge, well I guess rays are the way of the future, not depthmaps… :slight_smile: Even if I can just barely catch up to the look today, sometimes… in certain situations… it won’t last. Depthmapped spotlights are doomed, except for cartoony purposes, and maybe not even that will save it. I would have changed years ago if I’d had MR or Brazil or something… when the GPU comes of age we’ll be doing GI/FG/SSS/AO in real time. :slight_smile:

Just one example: look closely at the nose there - with depthmaps there would have been a lighter line just next to the nostril. Not to mention the flickering I always have to fight in animation. I know FG can flicker too, but this will improve in the future. Also, I would not be getting any bounce light. And the shadows are properly soft, not soft all over as in depthmaps, and using an IBL sure beats using a domelight… etc

And I’m still using my old shader here, anyway, just with a few new additions and tweaks.


#15

all quite good points.

i suppose i still have a lot to learn in both areas. i wonder if i would be wasting my time trying to achieve a nice look with traditional methods, or if i should pursue mental ray more.


#16

steven, the diffuse SSS node will work proper from IBL with secounday illum enabled. another trick with diffuse i like is you can put a black and white SSS map into it and remove unwanted sss effects.

also if you put mark davis SSS light mode on 3 i think it will work with the secoundary illumination


#17

hey steven, heres what ive worked up with diffuse shader, the skin network doesnt contain any lamberts, blinns, or oyan nayer.

i have no idea wtf it sup with the eyes, actuall y i have some idea but need to look more into the shading and there alignment lol.

anyway i think with another hour of tweeking here and there, i think i can get som of the pink skin tone down and really get something wonderful.

i had never had any luck with diffuse but i crapped my pants when i saw the ears and nose render out almost like silicon. the skin is starting to feel tangable. I have had much trouble with getting SSS impemented into a shader network and still have it pay respect to shadows, colors, and shading… this new setup seems to be solid.

btw the skin is entirely procedual atm, render time less than 2 minutes at this resolution.

i think i could bite that ear it looks so real for some reason. yum…


#18

ok this is posssibily the best skin network i have setup yet. I gotta go to work in 7 hours so i better get some sleep. im getting so much work done i dont wanna leave my computer lol.

i might have taken out to much pink i cant tell.


#19

nice shader kryoboy, that last one is really skinnylike :applause:

I have turned on ibl at last but, oh the horror, render times rocketed.
Its not that its not worth it but slow as hell.

Now I see I would need a raytracernode or something to blur the reflections,
haha ha, see you in a two weeks when I render this image.


#20

Very nice shader Kryoboy! :slight_smile: Love that translucency, can’t seem to get the same effect with that shader myself. This rendering looks a bit incandescent though, see if you can get the shadows a little darker.

Here’s what I got so far, FG with ibl, 2 spotlights. I took out the Oren-Nayar because it seems it was somehow causing the irradiance color to shoot skyhigh, even though I put it to zero… the dirtmap is integrated into the network, similar to yours. The Mark Davies shader is comped in post, together with my old translucency fake ramp shader. (That’s what’s causing the nose to glow, perhaps a bit too much). :slight_smile:

edit: the rendertime is 5 minutes total for the 2 passes