Tiling Textures | A Small Texture Set

A Small Texture Set

Back to the desert to create a texture set with cool variations.

We've created a tiling ground texture, and we've created a tiling brick texture. But we're not yet prepared to texture an environment, or even to texture the ground.

One tiling texture is rarely enough; they work much better in teams. Our ground texture may seem like an exception, but even in this case the ground of our environment will be more believable and more interesting if we create a set of textures to support the first.

With some experience you can begin to anticipate the kind of textures you are likely to need for texture sets, and form strategies for making them. This lecture will give you a good start.

 

Texture sets are groups of textures designed to be used together to texture an environment. A single brick texture does not a building make—you'll need textures for things like doors and windows. A brick building will often have some variations in pattern, such as a row of vertical bricks along the edge of the roof, or the base of the walls, or around shoulder height. We'll see examples of brick texture sets in future lectures.

Your ground texture will need some help if it is to be part of a believable environment. After you have made the effort to remove all conspicuous detail that might draw undue attention to the tiling, a single texture is still likely to create some patterns when tiled over a large surface. It may also look fairly bland and uninteresting, especially if you have removed too much detail.

You can break up the pattern and make a surface more interesting by adding one or two variations on the original texture. Such textures might not be noticeably different until viewed side by side with the original. A few more textures can be added that include details like large cracks or broken earth. The ground is rarely free of debris, so a good texture set will include a good range of things on the surface—stones, small plants, or bones, for example.

There is nothing technically significant about texture sets—they share a certain visual theme, and are designed to work toward a common goal, but the relationship is all in the mind of the artist, and with any luck, the game designer as well.

Applying Textures to the World

Textures in a set are all applied to an environment in the same way. At this point in your studies you have applied textures to 3D objects in Maya.

In most game engines and level editors, as in Maya, a single polygon can usually only have one material (and thus one texture) applied. There are some differences in game engines in the way that textures are applied to surfaces that have some impact on how texture sets are used. I'll give you some examples:

In the original PlayStation, the limitations of the hardware resulted in most PS games having certain similar characteristics. The PS did not include hardware perspective correction. This had far-reaching implications for games on the PS—the first being that you inevitably had lots of polygons which looked like these.

Lack of perspective correction meant that textures would shear along the center edge of a quad. 3D systems do perspective correction by their very nature—points, and thus faces, are always drawn in correct perspective. It is within the surface of a face, farthest from the points at its corners, that the perspective on the texture itself would be drawn inconsistently. The result is that the texture appears to warp and bend as the camera angle changes.

The only way to fix this is to make the distances between points as small as possible. This will mean more points and more faces, however, so a balance must be found. On some original PlayStation games, even the flattest surface was subdivided into quads of 64 units. In the image below, a surface that could easily have been composed of a single quad is subdivided into 16 quads, each 64x64 units in size.

Click the image above for a closer look.

One implication of this is that many more polygons are required to build even the simplest surface. The second is that it becomes convenient to "face map." Face mapping is a process by which a different texture is applied to each quad.

Since surfaces were all subdivided on the PlayStation, face mapping became a convenient way to apply texture maps. It is especially effective for any texture set that includes variations on a theme, because any single face can use any texture.

Even when subdividing a surface in this way, the warping of the texture still occurs. Wherever possible, artists would avoid having certain types of distinct detail in the center of the texture, especially bold horizontal or vertical lines. Throughout the environment, bold horizontal or vertical lines (such as the dark lines that appear between planks of wood) would be placed along the edges of the texture, and thus at the edges of the polygon.

Alternatives to Face Mapping

The easiest and quickest approach to mapping for games might be what's called world coordinate mapping (also called solid texture). Doom and the Quake series handle most mapping this way.

In this approach, textures have an absolute size. In the case of Quake III Arena, a texture map of 256 pixels square occupies 128x128 units of world space, by default. Apply any texture to a surface, and it will have this type of mapping applied. If the surface sits with one edge at 0,0,0, the center of the coordinate system, then the texture that appears on the surface will have one corner at that point—and the opposite corner at 128,128,0. Textures tile by default, so the entire surface will be covered by tiling the texture.

Because the Quake III Arena engine uses perspective correction, any huge, flat surface can be created using one "brush," each surface of which is composed of only two tris. The total poly count obviously benefits from this. To use an alternative texture (such as a variation on the original) to reduce the appearance of tiling would require using more surfaces.

The image below shows one simple texture (a white dot on a black background) tiled over the surface of a simple geometric shape.

In the image below the orange square outlines one instance of the texture.

The image below shows what must be done to introduce a new texture—new geometry is introduced so that the new texture can be applied. As you might imagine, when working in such a system the designer is less likely to use variation textures.

Expanding Your Texture Set

Below left is our ground texture tiled 3x3. You should remember our discussion about the process of removing conspicuous detail, and the effect that often has in terms of making the texture more uniform, and thus compromising its character, perhaps making it less interesting.

Below right is our color corrected source image. It shows all of the variation of color and pattern that nature gave the desert floor itself, at least a small part of it. We have done a good job with our texture, so it doesn't look unrealistic. But in some ways the source image is more visually interesting.

Click the images above for a closer look.

As we start to create a set of textures around a texture theme such as our ground texture, one of the first things we might consider is an alternate to our original tiling texture. We have already made a texture that tiles without showing seams which has a minimum of strong detail to draw attention to the tiling. A good second texture for our ground texture set might be a slight variation on this original texture that we could use to help break up further any pattern we might see when we tile the original.

The five tiling textures above (from UT2004) represent a small wall texture set. Any of these textures can be placed next to any other, and will tile seamlessly. Click each one to see it at full size.

A Texture Set Vocabulary

A while ago I tried coming up with names for the different types of textures commonly found in texture sets, rather than just using descriptions whenever I needed to talk about them. I decided to call the type of textures you made in Lectures One through Three "Base Tiling Textures."

A Base Tiling Texture, placed next to (or above or below) an exact copy of itself, shows no seams, and as far as possible, shows no indication that one is seeing a single texture tiled. This type of texture should show little or no conspicuous detail that creates a noticeable pattern when tiled across a large surface.

The type of texture I talked about at the beginning of the lecture I call a Base Tiling Texture Alternate—a variation on the Base Tiling Texture that tiles with the Base Tiling Texture (and with itself), but contains somewhat different detail so as to make it useful specifically for breaking up the repetition of the Base Tiling Texture. There may be more than one of these, but making more than two or three is not usually necessary.

If we expect to use a Base Tiling Texture Alternate often, we might consider making it tile much like the Base Tiling Texture, which tiles seamlessly, and has little conspicuous detail. Such a texture could be used by itself on a ground plane. Because it too will tile over a large area without obvious patterns, it is a viable alternate for the original ground texture.

Another option is to introduce to the Base Tiling Texture Alternate some of the character of the source image—I call this a Base Tiling Texture Variation. If we plan to use this texture only sparingly, then it can contain detail that would create obvious patterns if it were used more often.

It might be a good idea to create both tiles, which we'll do right now...

Creating a Base Tiling Texture Alternate

The image below shows my choice of a 1024x1024 portion of the color corrected source image, which I will use to create my Base Tiling Texture Alternate (as you may remember, we used a 1024 square pixel region for our first texture, and resized it to 512 square). I chose the area I thought looked the most interesting.

The image below shows my selection resized and pasted as a new layer over our original ground texture. It has been lined up precisely over one tile of the original texture, using the grid.

You will have to look closely to see the edges, but these new edges do create seams that will be visible when tiled, and will have to be dealt with. The most efficient way to do this will be to use the Eraser tool to expose the edges of the original texture. Remember to erase artistically, and make the new texture blend into the old as naturally as possible.

Below is our 3D test plane with the original ground texture applied.

Below is the test plane with the second ground texture added here and there for variation.

One texture of this type can add a little extra realism by adding some variation to the surface. This particular texture has a lot of character, and draws the eye a bit too much to be used often. As I mentioned before, you may need another Base Tiling Texture Alternate that shows as little conspicuous detail as the Base Tiling Texture itself.

Base Tiling Texture Variations

Base Tiling Texture Variations go beyond the Base Tiling Texture Alternate, introducing minor detail that increases the realism of the texture set. In a brick texture set this will typically include cracks, broken and/or stained bricks, small vents and such. Let's see what this might be in our ground texture set.

Below is another image I shot between photographing painted people and art cars at Burning Man. It is called "blackrock2.jpg" and is included in your course downloads.

Fortunately, I made note of the settings I used to color correct the other desert floor texture we worked with previously (don't fail to take note of this example of the value of making such notes!). If you need a reminder of the setting used, you can refer back to Lecture One.

There is a lot in this image I find interesting, and would like to include. It is wider than it is high, so a decision will have to be made whether to eliminate some of the detail on either side, or to make it smaller overall in order to fit. It doesn't seem worth it to make two textures that will always need to be used together in this case.

I started by resizing the color corrected source image to 512 in the vertical axis, and copying the results into a new layer in my 3x3 working PSD image. I wanted to see it in context before making my final decision.

In the end I decided to distort it a bit, as you can see below.

I used the Scale transformation here, pulling the right side in a bit.

With this texture we'll want to do some very careful erasing. The texture will look its best if we use a small eraser brush, and erase carefully around some of the small debris so that we have debris lying on cracked ground rather than compacted ground. This will make it blend better into the original ground texture. Closer to the edges this will be more important, as the transition from the top layer to the original texture takes place starting at the edges.

After some especially artistic erasing, we might end up with a texture like the one below:

Click the image above for a closer look.

The new texture in use with the others in our growing texture set:

The three type of texture we've discussed—base tiling texture, base tiling texture alternate, and base tiling texture variation—will give you a good start. But we're not done yet. Surface detail textures and set piece textures may be required to give your surfaces life. Let's look at those now.

Surface Details

Surface Detail Textures include detail necessary to create a realistic environment: windows and doors, including bricked-over windows and doors, for a brick texture set, and small plants and similar surface detail for ground texture sets.

Black Rock Desert is a fairly dry, lifeless clay lake bed. But that doesn't mean the ground for your game has to be the same. What do you think your creative license is for? The textures above add life to your environment in more than one sense—they make the surface more interesting to look at.

Set Piece Textures

But let's not depart from the whole lifeless theme too abruptly... if we're talking video games, death is never far behind, yes, including your own! Unless you're "lucky" enough to be working on the sequel to Barney Undersea, you'll probably be called upon as a game artist to include textures like this in your texture sets.

Source (left) and texture (right):

Click the images above for a closer look.

It took extensive and careful use of selections (and feathering) and the Eraser tool to remove the ground from the top image, so that the bones integrated well into my ground texture.

Sometimes you will include a texture, like this one, so interesting or otherwise likely to draw a lot of attention that you may only want to use it one time in the whole game. Such a texture I call a Set Piece Texture.

The Texture Set Palette

A few more textures and we have a small ground texture set. Below you see all nine textures in this set in a single image. I like to work on my texture sets in an image like this, in PSD format, with each detail in a separate layer. You might call this a texture set palette, in which you mix up your texture set one tiling texture at a time. Working in this way allows us to see the entire set as we work with it.

As you might guess, the principles for establishing a texture set we've just discussed can also be applied in creating geometric surfaces and texture sets.

You'll want to establish a base texture with alternate and variation textures, then think about what surface detail and set piece textures will add realism and interest to your texture set.

To wrap up this lecture I'd like to explore the challenge of creating joins between geometric textures, a challenge that's most clearly illustrated by attempting to model the end grain in wood.

End Grain
Important Ingredient of a Good Texture Set

End Grain is a term used to describe a texture created to solve a problem that is common to wood textures. It will be tempting to beginning texture artists to use wood textures like this:

You're not likely to see a wooden object in the real world that looks like this. A wooden object will usually look better if you create end grain textures for the corners.

Making textures like this requires some thought. You'll usually need a basic wood texture that tiles with itself, like the one below (this is the Base Tiling Texture for this wood texture set).

Three identical tiles. Click each of them for a closer look.

The two end grain textures need to tile seamlessly when placed end to end (as shown below, and on the cube shown two images above). The ends of the beams probably won't match naturally into the sides of the beams unless you take steps in Photoshop to make them do so.

Just in case we need to texture something small, the two end grain textures tile when the other edges are placed side by side as well!

Of course you'll also need the textures with end grain to tile seamlessly when placed next to the basic texture, as they appear below.

Take a moment, and think about what strategies you might use to make a set of textures likes this.

End Grain Is for More Than Just Wood

Consider the image below. The lack of end grain creates an unrealistic look. Some sort of end grain is needed.

With end grain the scene becomes much more believable.

With tiling textures we are often trying to make flat, computer generated surfaces look real. You should always use every means at your disposal to enhance the illusion. One good way to do this is through the use of end grain textures.

The texture used below doesn't have the sort of problems that the brick texture has without end grain.

But use of end grain can still improve the look.

End grain can also help with transitions from one surface to another.

I consider such textures to be a subset of End Grain, which I call Transitional Textures. This type of texture may share many characteristics of the End Grain Texture. The purpose of the Transitional Texture is to offer the most useful and realistic transition from one texture set to another.

Transitional Textures can be used in other ways to break up the very hard-edged, geometric look often associated with computer-generated imagery. Compare the two images below.

This effect is achieved by including a very thin, irregular piece of the ground texture along the very bottom of the brick texture. A little dust has been added to the bottom-most bricks as well. This thin piece tiles with the ground texture, creating a continuity between the two textures and the surfaces they're applied to that effectively blurs the hard edge of the geometry.

Click the image above for a closer look.

With these basic texture types in your toolbelt, you're better prepared to make useful texture sets.

Exercise Apply the concepts and techniques you've learned to create your own small texture set. Discussion Share your experiences in creating texture sets with your fellow students.