I have not given up on my little project. I did get a bit discouraged, there, but I've started experimenting again and I think I might be able to get something out of this either using render layers or possibly just simple (or simpler) meshes for each particle system. I may also need to go to more extravagant lengths, splitting things up into separate passes using scenes and then compositing them, which would be a pain. Anyway, I'm not giving up yet, but I don't have anything I want anyone to see.
Well, it looks like my system is not up to doing much with hair in the Cycles renderer. When I try to render my latest eyebrow attempts, the face disappears. A very disappointing turn of events, that. I was really looking forward to fooling around with the hair editing tools and getting some amateurish but at least interesting results.
I may be able to get something with the Blender Internal engine, but the whole lighting and material system is so much more fiddly and the results so unrealistic, it's really putting me off the whole exercise.
So, four days of struggle to get some kind of OK-I-guess lashes. Some lessons learned:
When using a multi-resolution modifier and adding a particle system (i.e. hair) on top, the level of the preview has to be the same as the render level. The particle directions are based on the modified geometry underneath, and if the level where you do the particle editing (the preview) doesn't match the final render level, the particles will go shooting off in unexpected directions. Until I realized this, I thought there was some bug with hair rendering that only happened in the final render (and not when the 3D view was set to render the preview). I spent a couple of days messing around trying to figure this out.
You've also got to turn on the "use modifier stack" on the emission control panel or particles (hairs) will come shooting out of weird places and directions.
In order to paint vertexes in the weight painting mode, you need to select faces (or maybe turn the face selection mask off?). Otherwise, it just won't do anything, which is not particularly useful.
The "physics" panel on the particle system settings is not about the physics of the hair, but of the particles that direct the hair growth. So you want the physics on and Newtonian. Then you can set the emission parameters to shoot the growth lines more or less straight out of the skin surface, or whatever else you want. In this case I actually had a small "normal" component and a small negative-Y "object" component, to make the lashes point out of the skin and forward. After that it was all fooling around with the particle editing tools (see next point).
Combing lashes is a pain in the ass.
Finally, and this was an even bigger pain in the ass, I was (am?) reaching the limitations of my system and/or Blender as things started getting very crash-y. Rendering would crash a lot. Switching back to the 3D view would crash. Saving might crash. Eventually, I found that if I dropped down the level of the multi-resolution modifier, things improved. So it seems like it is basically caused by having too much geometry to render. However, doing that meant (because of the first point above) that I would have to start over, since trying to change the multi-resolution modifier with a particle system attached would mess up the particle paths or (more usually) crash.
So, Blender is amazing, but not completely amazing (at least on a run-of-the-mill iMac). And now I'm worried how much I'll be able to do with eyebrows and hair. Still, onward.
A huge effort to get a couple of glints of light in an eye. Bump textures, noise textures, subsurface scattering, refraction... more complicated than the skin, even. At at the end of it all, I'm thinking I might move the light sources to reduce some of those reflections I worked so hard to get.
Anyway, the eyes are done for now. Next, either clothes (probably just a scarf to cover that horrible neck), or hair.
You would not believe the amount of time it took to just make her eyes brown. Well, making her eyes simply brown wouldn't have taken much time, but I had to lay the groundwork for the rest of the exercise in eye rendering, and that includes remodeling the eye a fair bit. So I only ended up getting a simple diffuse shader with a texture map of a basic iris.
Also today, I added a rim effect (a bit hard to explain, but based on the one in the tutorial) which I'm convinced is completely invisible.
Still, looking forward to adding a bit of life to those eyes.
It's really a bit crazy how much work it takes to get from one picture to the next in that series, especially since I would challenge most people to be able to tell the difference between any of them (except for the obvious background color change). From top to bottom:
First, the image from yesterday. This is an image used as a diffuse texture map, mixed with a pure white glossy effect to represent oil on the skin. That's it.
Second, I've added in sub-surface scattering (representing light that travels into and gets scattered from inside the skin). This is a single sub-surface scattering shader mixed with the diffuse color on the previous image and that result, in turn, mixed with the gloss. I think you might be able to see the effect if you look closely at her right nostril. Seriously, I'm not kidding. I doubt I'm going to go for a full-on three scatterer model for this exercise, because it's a whole lot of work for a minuscule effect. I'm fairly satisfied with what I got out of one shader, and I'll save fooling with the more complex and realistic treatment for some other time, maybe when I'm using stronger back lighting. (Honestly, I want to get on to the eyes and hair.)
Third, tweaking parameters on the gloss and sub-surface, adding a bump map to break up the gloss and make it look a little less plastic, though I'm not sure how well that worked, and also a mask to represent how skin tends to be more oily or sweaty on the forehead, nose and under the eyes compared to the cheeks.
Finally, adding a texture map (a reddened version of the diffuse texture) to control the sub-surface scatterer and restore a bit of the color variation (notice how the mole on her cheek is a bit clearer again in the last version compared to the middle two).
So, I think I'll call it a day with the skin shader and move on to the eyes for the next stage.
Checked the helpful Introduction to Cycles video and it cleared up a lot. Turns out materials make plenty of sense, I was just being confused by the way the older Blender internal renderer has a completely different way of setting up texture maps, and the tutorial I was following was using that for some things and Cycles for others. I've switched to focus on using the Cycles renderer for a more realistic look (and because it seems more sensible to me--I rather like the node editor, actually). The problems with the underlying geometry are getting more and more horrid looking as the materials and lighting improve, but I have to leave that for my next attempt, and finish this one first.
And it looks bad. It will probably continue to look bad. But seriously, what can I expect? Most of this has become an exercise in finding out how many ways things can be messed up only to discover so late there is nothing to do but ignore it and slog on.
Skin texturing is a bit of a mess.
Finding it very hard to wrap my head around materials and textures. I know how I think they should work, but the Blender UI does not behave that way, or so it seems.
Anyway, I got a recognizable pinkish blob to use as a basis for further fooling around. Someday I may even give her hair.