Tiling Textures| Advanced Texture Sets


Advanced Texture Sets

Build up your texture sets to create convincing game environments.

A texture set can be simple or include a great many textures—it all depends on the constraints of the project.

As a texture artist, you may be making the textures while another artist makes the 3D geometry to which they are applied. The art director or art lead will establish the guidelines for texture art.

Every new generation of games promises an increase in the total number of textures that can be used in a game, making tiling textures a vital ingredient. Your audience will always expect a more rich and immersive experience than what they were able to experience in games before.

Part of making a good texture set is the ability to make your textures usable in a variety of ways. By simply using your textures in various combinations to produce a variety of different looks, you can increase the richness and realism of your game world. A good texture set will make the illusion easier to achieve.

In this lecture, you can expect to:

Learn about the advantages of using texture sets over large texture images.
Learn to make textures that can be mixed and matched with others in your set for great variety and flexibility.
Learn how to tell when your texture set is complete.
Learn about the pros and cons of simulating lighting in a texture versus using bump and light maps.



















Larger tiles are wasteful of texture memory.
















Advanced texture sets can be mixed and matched to provide many variations, in organic or geometric textures.















Trim textures at the top and bottom of a surface can also yield variety.





















The level designer helps decide how a texture set will be used.

































The more variety in the environment, the less apparent the effect of texture tiling.




























































































Ideally, your textures should have no lighting; lighting should be supplied by the game engine.






The reality? Your textures may in fact have contrasts and shadows produced by specific lighting conditions. And that may be OK.

When designing textures, think about what kind of lighting will likely be used in the game engine.


Completing a Texture Set


Different Tiles for Different Detail

When working from photos, it can be tempting to take the easy way out: to simply create from a photo one large texture, and wallpaper a large surface with it. There are however significant disadvantages to this approach.

Consider the image below. This entire image tiles, so it is in fact a tiling texture. A big one.

A texture like this is very easy to apply, and all of this detail could be mapped onto one large quad. To match the texture resolution we've been working with, this texture should be 1353x1216 pixels—double this if we wish to work at twice the resolution of the required texture, as we have done so far. Of course, modern digital cameras can capture images of this size. This represents a rather large use of texture memory however.

It is wasteful, because most of the detail in the image repeats horizontally across the image. The basic brick pattern repeats vertically as well. Smaller tiling textures could be made of each part. There is also the disadvantage that this one large texture can only be used to create this one wall, while isolating different details to their own tiling textures allows for far greater flexibility.

We can break this wall down into seven tiling textures. Adding two end grain textures, we have a total of nine, two of which are 256x64, for a resolution of fewer than 768 pixels square—a substantial savings on texture space from the 1353x1216 pixels required for the texture above (remember, I am working at a base resolution of 512x512 with intent to scale down to 256x256).


These nine textures make up the walls below.

Notice the darker wall on the left above (darker because of the lighting in the environment, not because of the textures applied)—we already have available to us a simple variation on the original wall that would not be available if we used a single large texture.

Geometry for the bottom, middle, and top trim has been provided. This is an effective way to vary the look of surfaces textured with the same texture set. Trim textures like this are often not square. The bottom and middle trim textures shown above are 256x64. Resolutions of 256x32 or 256x128 are not uncommon. In this case there are two top trim textures, each 256x256. This is probably less common.

In most game engines, a single quad can only have a single texture map applied. Therefore the visible geometry cannot consist of two large quads (one for each visible wall). More polygons will be required for this texture set (that is, one quad will be required for each separate texture that is applied). In the image below the wireframe outline of the geometry is overlaid.

This is a worthwhile tradeoff. Nineteen quads is not a lot for a modern game engine. It is simple enough to vary the dimensions of the geometry in order to accommodate trim textures of different resolutions, and different building shapes and sizes.

It is worth noting that in many cases a level designer may be building the geometry, not the texture artist. The designer is likely however to understand the ways that textures and texture sets will dictate the way the geometry is built.

Here I've superimposed lines over my test geometry so you can see exactly how the tiles were arranged.

Expanding the Possibilities

By expanding the set we begin to increase the possibilities. Adding three more textures, and using the same geometry, we can create a different building in the same style, perhaps located in the same complex as the building above.

A few more textures and a slight change in geometry offer us another very different look to the top detailing of the building.

Windows are of course an important and distinctive feature. If we expand the set just a little further, we can begin to mix and match the various parts.

With the addition of the nine textures above, we can create a great many wall variations. Some of the possibilities are shown below.

Click the smaller images above for a closer look.

When Is Your Texture Set Complete?

This building is going to need a door. Most likely, your set should include several doors. There will normally be grand doors, for main entrances to the building, and more simple back or side doors.

You'll probably always find that as you begin to create geometry and apply textures you discover that more textures are needed. As an artist you will normally work closely with a designer who will apply your textures to an environment. You will need to try to anticipate the needs of the environment your designer is building. There will be textures in your set that the designer never uses, and there will be new textures that he or she requests along the way.

When I was working on Akuji the Heartless for the PlayStation, I worked closely with the level designer, and often made textures on request. I made one texture to be used on a ship, above the deck, on the walls that prevent the sailors from sliding off into the ocean (in some places there were railings, and in other places walls, the tops of which were probably just above waist height). It showed the same planks that were on the hull of the ship, but with large struts to create a more realistic look.

The designer immediately found a dozen uses for that texture that I had never thought of—walls inside of rooms, ceilings, the back side of almost any wooden surface. The number of uses for that texture expanded to a dozen and one when I showed him where I had intended the texture to be used!

Your texture set will thus often be complete only when the environment itself is complete. Even then, you may work on later levels in the game or its sequel, so you may well find a later use for textures you have made or discarded in your project.

Lighting in a Texture

Lighting is already "built in" to most of the textures in our set so far. Lighting is often an important part of the illusion. It contributes to the impression that the texture has some depth, as opposed to being the completely flat computer-generated surface that it actually is.

UT2004 features highly detailed environments and models, however sometimes detail is still added via textures rather than geometry. Note the horizontal concrete beams in the image above: the shadow under the top edge and the highlight above the bottom ledge give the appearance of more detail than is actually there. The same is true of the metal I-beams above. If you look at the edges of the beams (for example, where the I-beams meet the walls), you should be able to see where the illusion breaks down. Click to enlarge.
The same effect is at work on the support beams shown here. Click to enlarge.

Consider the textures below. Some parts are lit, others are in shadow. Even the ground texture below includes shadows cast by one surface onto another surface.

These shadows come from the original photographs. They can sometimes be too real. You will often have virtual lights in your game environments, and these lights will cast shadows. It can sometimes be very obvious if the shadows in your textures fall in a different direction than the shadows cast by objects in the environment. At the very least, you will want to be sure that the shadows in your set all fall the same way. Do you notice any inconsistency in the textures above? Perhaps you didn't notice this until I pointed it out. This is one indication of what you can get away with.

Ideally, anything that casts shadows will be geometry—all of your windows will be inset slightly from the walls, for example, and the window ledges will protrude slightly. As the power of game systems increases, the number of polygons that can be drawn increases, allowing much more detailed models to be created. This allows more and more of the lighting and shadows to be left to actual lights in the game, rather than simulating the effect by painting it into textures.

In some cases, you may want to include lighting in your texture that is emitted by objects represented in the texture. The example below is from a hypothetical "moonless night" version of our texture set, to emphasize the point.

Here light is emitted by the lamp in the texture image, not the actual lights in the game.

Light Maps

Most modern game engines can use light maps. Light maps are created by pre-rendering the lighting of the environment, and storing the lighting information in a large map that is applied by the game engine at render time. Light maps are often the most effective way to add lighting to textures, and you should usually use them when available, rather than add lighting to your textures as in the example above. Light maps will be explained in more detail in the next lecture.

Bump Maps

Another option involves working your textures to make the lighting more generic. You can create textures that don't include such strong shadows, and thus don't give an indication as to which way the light is hitting them. Sometimes a texture is painted so that the parts that protrude, that are closer to you, are lighter, and the parts that are recessed are darker. This is also a simple description of how bump maps are made...

Bump maps are image maps separate from texture maps that can be used by some game engines to further create the illusion of a 3D surface. The trick is done in the lighting; when the surface is rendered, the surface is shaded, using the bump map, as if bumps were present on the surface. The name is descriptive in that bump maps can add bumps to the surface, but not great depth. A brick texture is a good example of one that might have a bump map. Accompanying the brick texture would be a black and white image that shows what areas should appear to protrude (the bricks) and what areas should appear to recede (the mortar). We'll explore this idea more in Lecture Six.

Learn about the various types of maps that can be used in games.
Learn how transparency can be applied through transparency maps, alpha channels, and PNG file format.
Learn how bump maps, light maps, environment maps, and specularity maps interact with textures.

Apply the concepts and techniques you've learned to make your own advanced texture set.

Share your thoughts on your further adventures in the world of texture sets with your fellow students.