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Old 01-10-2013, 06:00 AM   #1
MarkNarwahlberg
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Photo realistic skin. Where to start?

I have a head model and I want to texture it so it looks photo realistic but I have absolutely no clue how to go about this since I'm sure just throwing a texture on won't work. Are there any good resources or tutorials you guys may know of where I can gain a better understanding for what I'm trying to do. If it means anything I'm using Maya 2013.
 
Old 01-10-2013, 09:12 AM   #2
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Googling Maya Mental Ray skin shading should give you quite a number of other people's experiment.
 
Old 01-10-2013, 09:39 AM   #3
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The Shading is definitely a big factor and there are plenty of tutorials around I am sure for the different renderers.

In terms of painting the maps it's actually pretty straightforward.
Find some good skin samples - 3d.sk is always good there. If you don't have access to polarized images you will have to retouch those images heavily to remove the highlights and shadows. Photoshop's shadow and highlight removal tool gets you to a point but after that you'll have to manually clone, adjust etc to create a nice result. Be careful of having a splotchy result. It can help to google polarized fotos of persons as reference but your difuse map is not necessarily going to look 100% like that.

After you're done preparing your images lock down some cameras from your model and bring the images into photoshop. Now spent a lot of time warping and positioning your skin textures to align with the features of the model. It can help to do this twice - once for the processed images, once for the unprocessed images (or just use the unprocessed first and then remove highlights and shading from there. Can be tricky though).

Now paint your displacement maps, tracing wrinkles, pores etc. This is where the unprocessed images come in handy as they tend to give you a better representation of what is really going on.

Paint things like veins separately so you have control over them later in the shader.

For displacement detail it can help to look at some scanned faces.

htttp://www.surfacemimic.com has some great silicon scans of faces (you can download some watermarked samples for free to study).

Also Paul Debevecs Lightstage stuff is always interesting to look at (http://www.pauldebevec.com/). Which leads us into specular Probably one of the more important things in skin. You could for example study the lightstage demo tool for facial reflectance parameters (available at Paul Debevecs page). With your color and displacement there you can get a base map established but you will have to adjust different regions of the face. In terms of parameters a lot of the subtle shifts in human skin come from super fine bumps on the skin, not necessary changes in the reflectance. Unfortunately when rendering you would need to render at insane quality to pick up these fine bumps if you were to do them in displacement/bump. So this is where you need play with your spec maps instead.
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Old 01-10-2013, 10:54 PM   #4
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Having reference pictures to pick colours off helps too. Here is a link to pictures of human skin colours;

http://humanae.tumblr.com/

There are several pages of them, click the "forth" link at the bottom of each page. You have to download each 500x500 pixel image individually, so pick the ones you think you will need.
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Old 01-11-2013, 12:24 AM   #5
MarkNarwahlberg
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Quote:
Originally Posted by Campi
The Shading is definitely a big factor and there are plenty of tutorials around I am sure for the different renderers.

In terms of painting the maps it's actually pretty straightforward.
Find some good skin samples - 3d.sk is always good there. If you don't have access to polarized images you will have to retouch those images heavily to remove the highlights and shadows. Photoshop's shadow and highlight removal tool gets you to a point but after that you'll have to manually clone, adjust etc to create a nice result. Be careful of having a splotchy result. It can help to google polarized fotos of persons as reference but your difuse map is not necessarily going to look 100% like that.

After you're done preparing your images lock down some cameras from your model and bring the images into photoshop. Now spent a lot of time warping and positioning your skin textures to align with the features of the model. It can help to do this twice - once for the processed images, once for the unprocessed images (or just use the unprocessed first and then remove highlights and shading from there. Can be tricky though).

Now paint your displacement maps, tracing wrinkles, pores etc. This is where the unprocessed images come in handy as they tend to give you a better representation of what is really going on.

Paint things like veins separately so you have control over them later in the shader.

For displacement detail it can help to look at some scanned faces.

htttp://www.surfacemimic.com has some great silicon scans of faces (you can download some watermarked samples for free to study).

Also Paul Debevecs Lightstage stuff is always interesting to look at (http://www.pauldebevec.com/). Which leads us into specular Probably one of the more important things in skin. You could for example study the lightstage demo tool for facial reflectance parameters (available at Paul Debevecs page). With your color and displacement there you can get a base map established but you will have to adjust different regions of the face. In terms of parameters a lot of the subtle shifts in human skin come from super fine bumps on the skin, not necessary changes in the reflectance. Unfortunately when rendering you would need to render at insane quality to pick up these fine bumps if you were to do them in displacement/bump. So this is where you need play with your spec maps instead.


Alright wow! There's a lot here to digest but I do have a few questions. I'll deal with shading later so for now I'll just start with texturing. I'm assuming I would UV unwrapping the head and import that into Photoshop? Then you said I should find, skin samples. Should I be piecing those together to form the skin for the head?
 
Old 01-11-2013, 12:44 AM   #6
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Sorry for all the duplicate posts. Cgsociety was having some issues and I can't delete it.
 
Old 01-11-2013, 02:54 AM   #7
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I honestly barely ever work on the flattened texture. Probably because I ave too many UV Tiles to deal with. I usually save out views of the asset and then work on those in Photoshop. After I am done I project this back on.
Mari has Projectors for that, Mudbox has "Export screen to PSD", Zbrush has it's view system under the "Documents" Palette, Bodypaint the "Freeze Viewport etc.

This has also the added benefit that you can change the model + UVs later and just need to reproject your maps.

And yeah, find skin samples (larger patches) that suit you. For a face you can take whole chunks from different pictures and reassemble them or use one face that suits your character and start modifying. For the body I would go for coverage first with something generic, then go from there and start adding in sections specifically, wrinkles etc. Complex parts of the body (hand, feet etc.) I would treat like the head.
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Old 01-11-2013, 03:13 AM   #8
MarkNarwahlberg
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Quote:
Originally Posted by Campi
I honestly barely ever work on the flattened texture. Probably because I ave too many UV Tiles to deal with. I usually save out views of the asset and then work on those in Photoshop. After I am done I project this back on.
Mari has Projectors for that, Mudbox has "Export screen to PSD", Zbrush has it's view system under the "Documents" Palette, Bodypaint the "Freeze Viewport etc.

This has also the added benefit that you can change the model + UVs later and just need to reproject your maps.

And yeah, find skin samples (larger patches) that suit you. For a face you can take whole chunks from different pictures and reassemble them or use one face that suits your character and start modifying. For the body I would go for coverage first with something generic, then go from there and start adding in sections specifically, wrinkles etc. Complex parts of the body (hand, feet etc.) I would treat like the head.


Luckily, I'm just going to be texturing a head. So just so I understand, I should export different views to PSD, and for each view, match textures over it, and then I can project those over my model? Also I'm using Zbrush so would I project in zbrush or could I use Maya?
 
Old 01-11-2013, 03:29 AM   #9
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Yep, at least that's how I would do it. You could use Zbrush's Projection Master or Spotlight to project back on. Problem in Zbrush is that it will always project in screenspace resolution - so even if you painted a nice 4k sized image of the face in photoshop, when you project it back on it will be at the resolution of your screen.

Are you polypainting in ZBrush or using Textures ?
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Old 01-11-2013, 04:10 AM   #10
MarkNarwahlberg
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Quote:
Originally Posted by Campi
Yep, at least that's how I would do it. You could use Zbrush's Projection Master or Spotlight to project back on. Problem in Zbrush is that it will always project in screenspace resolution - so even if you painted a nice 4k sized image of the face in photoshop, when you project it back on it will be at the resolution of your screen.

Are you polypainting in ZBrush or using Textures ?


I hadn't really decided either way. This is really my first attempt at this kind of thing, so I'm playing it by ear. What would you suggest, I can really go either way.
 
Old 01-11-2013, 04:34 AM   #11
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Hm. I would probably go projection master. This way you can use photoshop
No offense, but Zbrush is quite limted with its Layersystem. On a face you usually have enough resolution as a base but in the end you still will have to convert to textures to add in super fine detail. On the fly polypainting requires discipline in my opinion - you're tempted to just paint away instead of planning. You can always use it later to touch up stuff or use it as a temp method to get masks using Zbrush's surface aware brushes.
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Old 01-11-2013, 05:39 AM   #12
MarkNarwahlberg
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Quote:
Originally Posted by Campi
Hm. I would probably go projection master. This way you can use photoshop
No offense, but Zbrush is quite limted with its Layersystem. On a face you usually have enough resolution as a base but in the end you still will have to convert to textures to add in super fine detail. On the fly polypainting requires discipline in my opinion - you're tempted to just paint away instead of planning. You can always use it later to touch up stuff or use it as a temp method to get masks using Zbrush's surface aware brushes.


Cool thanks. I have a lot of work ahead of me but hopefully it pays off. Thanks for all the advice!
 
Old 01-11-2013, 05:43 AM   #13
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Try a few different approaches. I am sure no 2 people have exactly the same workflow.
What works for one the other might find less ideal.
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Old 01-11-2013, 03:51 PM   #14
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Quote:
Originally Posted by MarkNarwahlberg
I hadn't really decided either way. This is really my first attempt at this kind of thing, so I'm playing it by ear. What would you suggest, I can really go either way.


It's fairly common in ZBrush to use a texture for the head, and then sample a piece of the colour (place cursor over the colour you want to pickup, and click C) and roughly polypaint from the neck down. Colour Spray at low stroke and intensity is good for that. You can add finer details to the body when you export the texture to Photoshop.
As you can probably gather from the responses, there are a few ways to do it and you can pick the one that gives results you need.
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Old 01-12-2013, 02:29 AM   #15
MarkNarwahlberg
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Quote:
Originally Posted by Dillster
It's fairly common in ZBrush to use a texture for the head, and then sample a piece of the colour (place cursor over the colour you want to pickup, and click C) and roughly polypaint from the neck down. Colour Spray at low stroke and intensity is good for that. You can add finer details to the body when you export the texture to Photoshop.
As you can probably gather from the responses, there are a few ways to do it and you can pick the one that gives results you need.


Cool thanks! I might give that a try.
 
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