From eye-catching environments to eye-popping creatures, five leading artists reveal the secrets of creating professional-quality textures for modern games

The modern games industry is a competitive business, and one that offers diverse creative outlets for 3D artists. From professionals leading teams to the casual back-bedroom ‘mod’ enthusiast, there is an abundance of techniques to be learned from those working in the field.

It’s well known that games engines impose certain limits on texture sizes and colours. This is becoming less of a problem with the next-gen consoles and development kits, but the industry has been built around techniques to optimise art assets. These techniques form the basis of best practice and have been borrowed by the print, postproduction and animation businesses.

Since texturing is 99 per cent of the visual experience of a game, it’s vital to get your texture maps looking right – nothing breaks player immersion than the sight of a nasty seam. For this reason, developers prize texturing skills highly. It may not be as glamorous as modelling or animation, but many top games companies have stated that while they get plenty of artists who can model, what lets many prospective employees down is their texture work. So this issue, we asked five artists working in the field to reveal the tricks of their trade.

For the purposes of the article, we’ll assume that you already have a basic understanding of the subject, instead looking at tricks and techniques that are used in real production situations. Our examples are drawn primarily from environment work, but we’ll also look the process of texturing vehicles and creatures. We’ll be exploring a range of techniques, from quick ways to create variant textures to tricks for getting more out of your normal maps. Adopt them in your own work, and you should be able to hit the ground running.

UNDERSTAND YOUR CHANNELS
Artists will often fail to grasp ‘bump and spec’ and regard them merely as a couple of extra ‘toys’ which help the base texture look nice. This is a common error where next-gen texture creation is concerned. Whereas before there was usually just one texture which had to represent shadow, depth, and specularity, these elements now have to be represented on separate channels. The golden rule is that the diffuse map only contains the colour, the normal map the bumpiness, and the specular map only the shiny highlights. These elements shouldn’t be mixed across each of the channels or they’ll just end up cancelling each other out. [DC]

QUICK VARIANT TEXTURING
If you’re trying to maintain a natural and interesting feel to your game, variant textures can go a long away. Try to stay away from simple hue, saturation, or level shifting, but remember you don’t need to completely repaint the same creature three to five times. Varying big patterns like stripes and spots but keeping intricate patterns like fur and scales the same can make a big difference. Eye colour and other focal points like the areas around the eye and face are usually good to change as well. Usually these adaptations are enough to fool the viewer. [MF]

Image: © Microsoft Game Studios

USE PHOTOS ONLY AS REFERENCE
Recreating a reference image as a procedurally generated bitmap can be time-consuming and frustrating, so the temptation to create a nice tileable texture from a photograph and use it as a basis for the normal map can be overwhelming. However, the chances are that the photograph will contain shadows and therefore the end result will look wrong. A shader authoring tool such as DarkTree will help you generate procedural textures which can be scaled to any size, unlike a photograph, which will look lossy (lo-res), when scaled upwards. [DC]

USING RENDER TO TEXTURE [1]
Another common method for texturing is ‘texture baking’. This can give you a good head start when creating maps in Photoshop. In 3ds Max you can find this option by choosing Render > Render To Texture – this is where you would also bake out a normal map. By pressing Add under the output rollout you can see a selection of render elements that are available. If you add new render engines to 3ds Max they will each offer new render elements, along with normal and height maps. However, another great map to render here is a colour map (the Diffuse map in 3ds Max). If you have an object with many different pieces, you could apply a different diffuse colour to each part, then when all the parts are attached and a diffuse texture element is rendered ,you’ll have a map made up of all the various surface colours your model has. The benefit of this is that back in Photoshop you can very easily make selections based on the different colours. [SM]

USING RENDER TO TEXTURE [2]
Setting up a good radiosity solution and letting that be a guide can go a long way to helping your texture generation. If you’re using 3ds Max, you typically want to set up a Sky light; if not, anything that generates a sphere of lights around your object. Make sure shadows are on, and that you choose an appropriate light colour, and Render To Texture. The result will be a great starting point for painting shadows. Alternatively you can set it to Multiply in Photoshop and layer it on top of your texture, adding that extra bit of realism. [MF]

USING RENDER TO TEXTURE [3]
By rendering textures in a package such as 3ds Max, you can be sure that the normal map the software generates is precise because it has the data to interpret the geometry accurately. Become familiar with the Material Editor and, where time allows, use procedurally generated textures to apply to the geometry you are rendering. Rendering your textures this way also gives you the option of using ambient occlusion, which will help add some depth to your colour map without generating shadow. [DC]

IMPRESSIVE EMISSIVE MAPS
Whenever you want to achieve a glowing or radiating effect on a surface – for instance, for a magic sword with an inscribed glowing design, or a flickering fire – an emissive map is the way to go. The screengrab below shows a colour texture used for a building in the Obsidian Edge 2 mod for CryEngine 2. The building had to appear lit from the inside when seen at night, so we duplicated the texture and masked away areas that should not be affected. The windows left black would be seen as unlit windows and those left brighter would appear lit.

Images: © Stefan Morell

The masked image was then copied to the Alpha channel of the colour texture in Photoshop, and a shader was used inside the game engine to take best advantage of the glow effect. The top image shows the final real-time rendering in CryEngine 2. This kind of night-time view would look very flat if there were no emissive maps on the windows. [SM]

PAINTERLY AMBIENT OCCLUSION MAPS
Typically, ambient occlusion (AO) maps are separate maps that act much like shadow maps, dark maps, or light maps. However, an AO map functions in real time and prevents ambient light from hitting the model wherever there are shades of black in the map. These types of maps can be very helpful in defining form, but it’s important to maintain an interesting shadow colour. Adding blue, purple or green to your shadows can add a lot of vibrancy and interest to your objects at a low cost. Unless you’re going for a very harsh, stylised lighting scheme, black or grey shadows can kill the colours you have in your diffuse channel. It’s also good to keep in mind the old painter’s rule of thumb that, visually, warm colours come forward, and cool colours recede into space. [MF]

QUICK SKYDOMES IN VUE INFINITE
Vue Infinite is great at procedural skies and terrains, but it’s also extremely handy if you need to make skydomes for your game environment. In Vue Infinite, choose File > Export Sky from the menu. This will offer an option to render a skydome, or create cube maps. These are great for generating ‘fake’ reflections in real-time applications. [SM]

AVOID PHOTOS WITH HARSH LIGHTING
When using photographs to make your textures, try and use images that have no harsh lighting and shadows: otherwise, you will have to spend a lot of time erasing them in Photoshop. Ideally, you want to be able to start off with a light-neutral photograph and then either paint in shadows and lights yourself or rely on the game engine to do it for you. Avoid painting textures from scratch as it’s almost impossible to re-create the tiny details you see in a photograph, and extremely time-consuming, to boot. [BC]

Image: © Sony Computer Entertainment Europe

A fine example of professional texturing, created for SCEE‘s Pursuit Force: Extreme Justice, developed by Bigbig Studios. When creating similar scenes, avoid basing textures on photographs with harsh lighting

DON’T ABUSE THE NVIDIA PLUG-INS
In terms of production, Nvidia’s Normal Map filter is a very quick and effective tool for generating normal maps, but only if it’s used correctly. If you’re going to use it quickly, for example, to run on an image such as a photograph, which already contains shadow information, the chances are that those same shadows will be interpreted as ‘depth’ in the bumpiness, which will be wrong. Similarly, any specularity in the image will also come out bumpy. Used correctly, the Normal Map filter is an effective weapon in the texture artist’s canon of tools, but if it’s abused it will blow up in his face. [DC]

PHOTOSHOP FILTERS [1]
Found in Photoshop CS2 onwards, Pattern Maker is a handy filter that will help create tileable textures quickly and with minimal fuss. Simply drag a marquee around the area of the image you’d like to sample, copy it to the clipboard and then paste it into a new image. Select Pattern Maker from the Filter menu and, with the tick box selected, simply hit Generate. Now you can touch up the image so that it doesn’t repeat too much. Remember, like any tool at your disposal, don’t abuse it! Creating a tileable image to run the Nvidia Normal Map filter over just won’t hack it for a next-gen texture, for the reasons outlined in the previous tip. [DC]

PHOTOSHOP FILTERS [2]
The High Pass filter (Filter > Other > High Pass) is an often overlooked Photoshop tool. You can use it to help even out the extreme dark and light spots that often occur in textures sourced from photos. The more even the lighting is, the better the texture will tile over larger distances. [RJ]

PHOTOSHOP FILTERS [3]
Once you have made a texture that you intend to tile, but are unsure if there will be a seam between the edges when you do so, you can check in Photoshop by clicking on Filter > Other > Offset. From here you can choose how much you want to slide the image across the canvas and will be able to see if there are any obvious seams. [BC]

BETTER NORMALS WITH CRAZYBUMP
The software tool CrazyBump can be used to produce good-looking normal maps straight from photos. This can save you time, as you don’t need to model out every texture.

At Splash Damage, we used CrazyBump a lot for the geological textures in Enemy Territory: Quake Wars. We had a difficult time getting the rock wall textures to look good, and went through a lot of techniques to try and achieve a good result; CrazyBump enabled us to get some great results in a fraction of the time. Often it works much better with a photo that has a strong sun direction, rather than the ideal overcast flat lighting you need for a diffuse map. [RJ]

Image courtesy of Splash Damage

An in-editor shot of a rock wall. The in Enemy Territory: Quake Wars team had a lot of trouble creating the rock texture, but CrazyBump helped to make the job much quicker

ADD DEPTH WITH PARALLAX MAPS
Parallax occlusion mapping could best be described as ‘normal mapping on steroids’; by using a height map (usually placed in the Alpha channel of the normal map) it can add extra depth to a surface. It’s best to use this effect in very subtle ways as texture distortion becomes obvious when the viewer gets too close. If you’re generating normal maps from hi-res models in ZBrush or Mudbox, you can use the displacement textures as a parallax map alongside your normal map. Next-gen engines such as Cry Engine 2 or Unreal Engine 3 can take advantage of parallax mapping. [SM]

KEEP TEXTURE RESOLUTION IN MIND
Consistent texture resolution is a big part of making a game feel cohesive. Everything on screen should have as close to the same level of resolution as possible. Otherwise, a blurry texture appearing next to one which has high resolution which will have a strange effect on focal point, disrupt the overall feel, and in extreme cases, cause unnatural artefacts. [MF]

USE INDEXED COLOURS
One of the most important things in the games industry is memory: usually we can’t get enough of it. Keeping texture sizes down is very important, so it’s handy to know about bit depth. You can select what bit depth you want your textures to be in Photoshop. Once you have created your texture and saved it out as a TGA, go to Image > Mode > Indexed Colour. From here you can specify exactly how many colours you want in the image. Select either Local (Perceptual) or Local (Selective) and then define the number of colours. For a standard PSP 128×128 texture, saving it out as a 4-bit image knocks its size down form 40kB to just 16kB, though you do tend to lose some detail. A PSP 256×256 texture saved out as an 8-bit image (256 colours) goes from 128kB to 64kB. When you enter the realm of next-gen, textures can be as high as 32-bit – 16 million colours, plus a transparency saved out in the image’s Alpha channel. A 512×512 texture of that resolution comes in at 1MB: the same amount of memory as 64 individual PSP-resolution textures. [BC]

THE EXPERTS

BEN CALDERWOOD
Ben has been working in the games industry for just over a year as an environment artist for Bigbig Studios
www.bigbigstudios.com

DAVE CULLINANE
Dave, environment art manager at Pivotal Games, is responsible for the quality and timely delivery of its in-game assets
www.pivotalgames.com

MITCH FLETCHER
Mitch has been working in the games industry for five years. He is currently lead artist at Blue Fang Games
www.mitchfletcher.com

RICHARD JOLLY
Richard is co-founder and art director at Splash Damage, creators of Enemy Territory: Quake Wars
www.splashdamage.com

STEFAN MORRELL
Stefan is a freelance digital artist currently working as environment artist on a CryEngine 2 mod
stefan-morrell.cgsociety.org/