In this texture painting tutorial, I will be describing some of the techniques I use when creating realistic skin for creatures in my day job as an artist at Framestore.
I use Mari as my main paint app – it's become the industry standard – so Mari tools are what I will refer to. While this tutorial can't cover every aspect, but it is a broad overview of how I work.
I've been painting textures for feature film VFX, and previous to that television, since 1996, and my experience is in that realm, but the basic theory applies to any photoreal rendering. Rather than use one texture as an example, I'll describe the process in general terms illustrated with various different examples.
Sep 08, 2017 In this Exploring Bodypaint 3D - 3D Painting, Image Editing and More movie, I show you some of the powerful features and capabilities of BodyPaint 3D. This is a 3D application that can be used on.
There are many rendering platforms out there, each with their own characteristics, but after having painted texture maps to be rendered with mental ray, PRMan and currently Arnold, I've found the general principles to be broadly similar.
It's always a trial and error process, to see what works and what doesn’t. But something to bear in mind is that it needs an educated guess to judge whether your texture will look as you'd planned in the render, with all the shader and lighting work in place.
What looks good in a texture map, may not be right for the shots that the asset will end up in. Having said this, it makes sense to have a texture map look as good as possible when viewed in your paint software.
01. Use reference
Something I tell people with great passion, is never make it up. No matter how alien your creature may be, it needs to be grounded in the real world. I have a huge library of photographic images and look at it constantly for inspiration.
A lot of creatures will require wrinkly skin, so look at wrinkly subjects – elephants, rhinos, old people, monkeys with alopecia... all have relevance.
02. Devil in the detail
Look at the shots that your asset will inhabit and tailor your texture maps accordingly. If it's on screen for a few seconds, in the background and motion blurred, then don't waste time painting detail that won't be seen.
Remember that a turntable is great for establishing the aesthetic of your creature, but this render won't ultimately be the finished product. Put in as much work as you think it will need, add a little more for safety, and use your time wisely.
03. The UV layout
It’s important to make sure that the UV layout of your model is going to properly utilise the space of the UDIM tile. Try not to leave too much empty dead space but keep elements in a logical place, for example teeth in their own tile.
Try to have the anatomy flow across the UV layout in a logical manner. It sounds obvious, but even though you will probably be painting in a 3D space, it makes sense to still have the layout flow in case you do some 2D painting directly into the tiles.
04. Use a template map
I start the process by painting a map I call the 'template'. This map is never used directly to render with, but establishes a monochromatic description of detail that incorporates the basic layout of skin folds, scales and so on.
It provides the basis for most of the subsequent map types. I tend to make it an earthy brown tone, and is created using hundreds of photo-referenced skin pieces, composited together to flow over the model in a naturalistic way.
05. The initial map
I either use Mari's Paint Through tool or I set up projection cameras and export these images to paint in Photoshop. I export an unlit COL map layer and a lit grey render to use as a guide, then I layer them with the grey lit render on top using a hard light layer.
The two images mix and appear as if you were painting in Mari’s paint buffer. Experience has given me the instinct to judge which method will work best.
06. Ataining realism
Animals get dirty, they scrape and scratch and pick up all sorts of damage, wear and tear. I paint this detail on a separate layer, using both texture brushes and photo reference applied with the Mari Paint Through tool. Never make it up.
Observe all the details if you want to make it believable. For instance, look at the way a tortoise sheds skin and becomes white and flaky in the cracked/recessed areas. To become a great texture artist, you need to become familiar with the patterns that nature creates.
07. Create a bump map
Here's where the earlier template comes in handy. I copy this channel and paste it in to a new Mari channel. Desaturate it and begin to transform it in to a bump map. It shares the same source as the Colour map, so it will match all the relevant details.
I use the Levels filter to change the contrast. Be careful the grade doesn’t crunch out detail at the far ends of the range – you don't want to lose detail in the light or dark areas. This initial grade will get you part way.
08. Tweak the map
Next I use the Dodge and Burn tools to bring out the lights and darks, and eliminate the patchy variation that's inherent. I also paint a series of masks with a Soft brush to selectively grade areas.
I use Photoshop for this. I like to layer the bump map over the colour map and flick between the two to see how they relate. Some details are shared between the two maps, but some not.
09. Avoid overdoing it
Spots and blotches don't belong in the bump map, but small skin folds and cracks do. Those folds and cracks may have collected dirt and so will be visible in the colour map.
Exercise caution, you don't want a lit look, with shadows evident in the colour map. That will create a doubling up in the lighting shader and create a fake appearance.
10. Specular
Specular and specular roughness (SPC and SPR) can both be extracted from the bump map. They will need a lot of paint attention to make them work as specular maps, but if they derive from the bump, the detail will relate.
The SPC map will need to be darker where the dirtier areas are, and lighter where the cleaner, more reflective areas are. This may coincide to some extent with the scaly/wrinkly pattern, as dirt may collect in the crevices, and the raised areas may get a buff and be shinier. It's a general rule of thumb, but you need to make judgment calls.
11. Specular roughness
The SPR, is doing a similar thing to SPC, except the tonal values don't determine specular intensity, they denote specular highlight falloff, or softness. Black areas in the map create a tight specular hit, and white areas a more scattered, diffused specular.
Typically, the SPR will be a broader, less detailed map, as it dictates which general areas are more or less shiny – like the slobber around a creature's mouth and lips.
12. Displacement (DSP)
Sometimes, it's a good idea to create a displacement map after the texture maps are painted. This gives you free rein to paint a scale/wrinkle pattern in the bump map, drawing directly from photographic references.
Then take this map and generate a displacement map to conform to it. Using this approach will save time, and also allows a naturalistic photoreal layout of the skin's micro folds patterning.
![Reference Reference](http://c4d.cn/help/c4dcn/cn/pics/__tut_024245.jpg)
13. Other maps
In addition to the basic set of maps, there are also sub-surface, ID masks, iridescence... the list goes on. All of these have their place: human skin, for instance, needs sub-surface to give it a translucent feel.
Skin colours change depending on how much light penetrates the skin. There’s blood in the veins and fat under the skin. These maps are less intuitive as they don't appear in a Mari shader set up, but to give a creature life they play an important role.
14. Fit for purpose
It’s tempting to paint a lot of superfine micro detail in a texture map, so it can take an extreme close-up and still hold up. This is a good thing, but you shouldn't lose sight of the bigger picture.
A texture map will also need to work in mid- and long shots. Sometimes that micro detail will disappear in certain scenes. You should take a step back frequently and zoom out to see if it's still working at a distance.
Words: Daren Horley
Originally from a traditional illustration background, Daren switched to digital VFX in 1996, and now is head of texture at Framestore, London. This article originally appeared in 3D World issue 182.
I've said many times that it's a really great time to be a texture artist. Over the past two or three years, a slew of new texturing, re-meshing, and UV mapping tools have emerged that have made the once tedious process of surfacing a 3D model a lot more enjoyable. Whether it's a one-click UV solutions, or a sophisticated 3D painting app, you're bound to find something on this list that makes you like texturing just a little bit more:
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Scultping/Versatile
While the chief use for each of these three packages is digital sculpting and high-poly detailing, they all do much more than that. Each of them has its own strengths and weaknesses, and while ZBrush is certainly the most ubiquitous of the three, they're all worth checking into. Their usefulness in a texturing pipeline comes primarily from the fact that they can be used to add an incredible amount of detail information to your model, which can then be baked down into diffuse, normal, ambient occlusion, and cavity maps. All three of these also have 3D painting capabilities for seamless texture painting.
ZBrush - ZBrush wears many hats, obviously. I think most artists would say that it's best-in-class for sculpting, and it's honestly only a few steps away from being an all-in-one content creation package. Learning ZBrush is a safe bet no matter what position you hold (or aspire to) in the industry.
Mudbox - Everytime I start to think that Mudbox is an also-ran in the sculpting game, I learn of another top-tier artist that uses it instead of ZBrush in their workflow. The apps share a lot in common, and where ZBrush excells in sculpting and detailing, Mudbox has better painting tools and an easier interface. They both get the job done, but I'll say this—Mudbox is almost universally recognized as having a better workflow for painting diffuse textures directly on the surface of your model. Many liken Mudbox's painting tools to a 3D version of Photoshop, and that's really saying something.
3DCoat - I don't use 3DCoat, but I checked out all the documentation on their recent Version 4 beta release, and it's shockingly impressive. 3DCoat is way closer to parity with ZBrush and Mudbox than I though, and even beats them in certain regards. It's significantly less expensive to boot.
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3D Painting
- BodyPaint 3D - a 3D painting app developed by Maxon with some fairly unique features like multi-channel painting, the ability to use Photoshop brushes in 3D, and ray-traced previews while you paint. Definitely a step up from most integrated 3D painting tools (like Zbrush's poly-paint).
- Mari - Super-expensive 3D painting tool developed for use in high-end film pipelines. It supports ridiculously high resolutions and boasts some impressive film credits, but it's probably a bit out of reach (and frankly, overkill) for most individual artists.
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Map Generation/Baking
These apps are primarily used for baking high poly details onto a low poly mesh, generating ambient occlusion and normals from a bitmap image, and creating procedural textures:
XNormal - XNormal is pretty much the tool of choice for baking details from a high poly mesh onto a low-poly target. The software is free, and I doubt there's a single game artist on the planet who hasn't used it. Fantastic for baking normals, and in my opinion the AO maps it generates easily beat what you can get from Knald or nDo2, even if it does take a bit longer.
Substance Designer - Substance is a fully featured procedural texture generator that uses a node based graph workflwo to help you create unique tiling textures. I just started using Substance recently—it's just a blast to work with, and it's incredible how quickly you can get a great looking tileable map out of it.
Knald - Knald is a brand new map generation tool that uses your GPU to render out AO, cavity, convexity, and normal maps from any bitmap image or heightmap. Knald is one of the best tools of its kind, and has one of the best real-time model viewers out there. Plus it's crazy fast.
Crazybump - Crazybump is a very, very similar predecessor to Knald. It's been a popular tool for a long time, but it's really starting to show its age. I just think you get better results out of newer apps like Bitmap2Material and Knald.
nDo2 - nDo2 is Quixel's flagship normal mapping plugin for Photoshop and allows you to create highly customizable normal maps just by painting them on your 2D canvas. While nDo isn't the first piece of software that can generate normals from a 2D image, it does offer the highest level of control by far. nDo2 can also bake ambient occlusion, height, cavity, and convexity maps from your normals.
dDo - Also from Quixel, dDo is as close to an 'automatic texturing' application as it gets. While dDo mostly delivers on its promise to give you usable texture bases in mere minutes, the quality of the results it returns is directly proportional to the information that you feed in. In other words, the software still requires a skilled operator. dDo works well as part of your texturing pipeline, but don't let it become a crutch.
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Remesh/Retopology
Even though retopology has more in common with modeling than texturing, I still consider it a part of the overall surfacing process:
Topogun - Topogun is a stand-alone mesh re-surfacing tool, which also happens to have map baking capabilities. This has been a favorite tool with game artists for many years when it comes to complex retopology tasks. Although hand-made retopo has become unnecessary for certain assets (a low-poly rock, for example), Topogun is still a very good option for complex character remeshing.
Meshlab - Meshlab is an open source solution for mesh processing tasks like polygon reduction and cleanup. Honestly, it's more useful for 3D scan data, however it'll work in a pinch for mesh decimation is you don't have access to ZBrush, 3DCoat, Mudbox, or Topogun.
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UVs/Mapping
Nobody likes creating UV maps (ok, maybe someone does), but these plugins sure make it easier:
Diamant Modeling Tools - Diamant is a pretty fully featured modeling plugin for Maya that also happens to include some pretty awesome UV tools. In fact, the tools included with Diamant are quite comparable to what you get with Headus, Roadkill, and Topogun, but you never have to leave Maya because it's all integrated. Of course, if you're a Maya user this won't help you much, but I quite like it!
Maya Bonus Tools - MBT are a list of tools for Maya that Autodesk distributes 'as is,' meaning they aren't officially supported. But they're incredibly useful and include an auto-unwrap UV tool that easily beats anything else included with Maya. There's a lot of overlap in the bonus tools with other plugins like Diamant, but Maya Bonus Tools are free so you really have nothing to lose by taking the time to install them.
Headus - Headus UVLayout is another standalone mapping tool. At one point, this was hands down the fastest UV tool in the game, but a lot of other packages (like Maya Bonus tools, Diamant, etc.) have caught up quite a bit. Color feedback for UV stretching is a nice feature.
Roadkill UV Tool - Roadkill is a standalone UV mapper for Max & Maya. It's a bit antiquated and no longer being developed, but it's one of the few tools with a (very useful) UV stretch shader.
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Marmoset Toolbag
And last but not least—Toolbag is a standalone real-time renderer, and while it isn't a texturing tool per se, it is undoubtedly the fastest and easiest way to prototype your textures in a quality real-time engine. Marmoset has high-quality lighting presets, tons of post-processing options, and is a heck of a lot quicker than loading up your model in UDK or Cryengine just to see if a WIP is (or isn't) working.