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3D DIRECT • August 14, 2000

The Artist's Canvas

Flat versus Deep: Faking Depth in Texture Art

by Eni Oken

Texture art is an often misunderstood and unexplored area in 3D, only recently gaining recognition. Largely responsible for the final look of any 3D model, textures not only give personality to the work, but also increase realism and add character to a model.

One important aspect of textures is the depth of the elements in the texture, a quality which can also be called dimensionality. A texture is a piece of art like any other, and, as such, can have a more dimensional or flatter feel.

Figure 1 shows the difference between two similar cartoon-like textures—one has no dimensional feel at all, while the other seems to show certain features that pop out of the image. The depth is obviously illusory, caused by certain characteristics present in the image: the circles in the second image possess highlights on the upper-left side, and shaded darker areas in the lower-left side. This alone would make the circles look dimensional, but combined with the simulated shadow being cast on the background, makes the objects stand out much more. To increase even further the illusion of depth, certain circles are overlapping and casting shadows on others.

Figure 1: Two versions of a cartoony texture. Figure 1a shows a flat version, while Figure 1b shows a very dimensional version. Image courtesy Eni Oken and copyright Eni Oken.

This fake depth can be advantageous if the artist knows when and how to apply it. If used properly, fake dimensional details can decrease modeling time and enhance the amount of detail and realism in a scene.

When to use deep or flat textures: prerendered versus realtime

Although it may seem pretty obvious to a more experienced 3D artist when to use or not use dimensional elements in texture work, many beginners need to understand the difference between the essential types of 3D work first:

1. Prerendered 3D in still imagery and animation is often used for print (magazines, books, advertisements), broadcast, film, and game cinematics. Prerendered 3D usually has a high degree of modeled detail. Both models and texture work are highly detailed. The final image or animation is prerendered; that is, is preprocessed by the computer in a final camera shot. The advantage of this type of work is that it allows for extreme control on the artist's part, as viewers are only permitted to see one camera angle. Disadvantages are that detailed models can be very time consuming to create.

Although not widely adopted, texture depth can be useful for still imagery, reducing some of the modeling time. However, if not made to match with the current lighting in the scene, the viewer may be able to detect the fake (see Figure 2). In animation, this is a particularly vulnerable area because camera movement shifts point of view often, therefore increasing the chances of a bad side camera angle that would display the fake.

Figure 2: The textures that are seen straight ahead look convincing; however, a bad camera perspective makes the fake perceivable (side walls). Image courtesy Eni Oken and Copyright Eni Oken.

2. 3D in realtime interactive projects is most commonly seen in realtime video games, but is also developing rapidly for the Web. Realtime 3D allows for extreme viewer interaction and movement, but due to hardware and bandwith constraints, still does not allow extensive modeling details. This is where dimensional textures are mostly adopted—in a realtime project almost every single texture has dimensional elements added to it. Despite the fact that viewers can move close to the texture and position themselves in viewpoints that can clearly perceive the fake depth, freedom of movement seems to make up for the perspective flaws, and extremely dimensional textures are widely accepted for this kind of project.

Figure 3: The interior of a realtime environment for an online community world for the Web, along with the very dimensional textures used for each wall. Image copyright 1998 Worlds, Inc.

Levels of depth

Although dimensional textures seem more suitable for use in realtime projects, animation and still 3D work can still benefit from depth if carefully applied. Dimensional textures do not have to be shockingly dimensional—they can be very subtle. The depth can vary, going from almost flat, with some depth in the grain of the texture (see Figure 4a), to more obvious grain and subtle dark shadows (see Figure 4b), to openly distinct dimensional features (see Figure 4c).

Figure 4: Levels of depth can vary from almost flat, somewhat dimensional, to extremely dimensional. Image courtesy Eni Oken and copyright Eni Oken.

First level: adding grain to a texture

There are different ways of adding a bit of grain to a texture. If you own Corel Painter, (formerly MetaCreations), then use the command Effects, Surface Control, Apply Surface Texture, with the option Image Luminance. This command applies an embossed effect over the image using the image's own luminance to control the dark and lighter areas (see Figure 5).

Figure 5: Use the Surface Texture command in Painter 6 to produce a slightly embossed effect over the texture. Image courtesy Eni Oken and copyright Eni Oken.

If the image does not have very good contrast in light and dark areas, then choose the option Paper, which also yields good results.

If you do not own Painter, then you can use Adobe Photoshop to produce a similar effect:

1. Duplicate the image's layer by choosing Layer, Duplicate Layer.

2. Apply the command Filter, Stylize, Emboss on the top layer. You may need to use high values for the effect to show.

3. Change the top layer's mode to Hard Light, and observe the embossed effect over the bottom layer.

Figure 6: The embossed effect can also be achieved using Photoshop and the Emboss Filter. Image courtesy Eni Oken and copyright Eni Oken.

Second level: adding subtle dark shadows

Another way to add a bit more depth to certain areas of a texture is to add dark shadows around elements that you want to enhance. Consider the two textures in Figure 7, both similar, however Figure 7a seems much more dimensional due to the added dark edges around the tile-looking elements.

Figure 7: Dark shadows around certain features add depth to the texture. Image courtesy Eni Oken and copyright Eni Oken.

Using Photoshop, this can be very easy to accomplish by using the airbrush tool with a dark color. Pick an almost black (but not totally black) complementary color to the overall color tone of the texture. Airbrush around the perimeter of the detail lightly, in irregular dabs. The irregularity increases the realism and breaks the computerized feel.

If the element you want to enhance is placed on a separate layer, then use the following method:

1. Duplicate the layer by choosing Layer, Duplicate Layer.

2. Check the Preserve Transparency box in the Layer panel for the bottom duplicate layer.

3. Choose a dark color and use Image, Fill, Foreground Color.

4. Uncheck the Preserve Transparency of the bottom layer and apply a Filter, Blur, Gaussian Blur to fade out the color.

Third level: obviously dimensional features

If you are interested in creating features that are obviously dimensional, then you can use Photoshop 5.0's (or higher) Effects panel to apply a Bevel:

1. Create the feature that you want to enhance in a separate layer.

2. Choose the command Layer, Effects, Bevel, and Emboss option. Adjust the parameters Depth and Blur to control the amount of depth and sharpness of the edge.

3. Apply another Effect, the Drop Shadow, to enhance even further the sensation of depth (see Figure 8).

Figure 8: Apply obvious depth to certain features by using the Layer, Effects in Photoshop.

Conclusion

Dimensional features are very well known to the game industry; however, other areas of 3D such as film and animation can certainly take advantage of this feature if used with care. Dimensional features can save a lot of time in production, cutting down modeling time considerably.

All images are courtesy Eni Oken and copyrights are of their respective owners.

Eni Oken is a freelance 3D artist based in Los Angeles. As an architect with 13 years of experience in computer graphics, she has participated in the creation of 3D art for numerous interactive projects and has won several awards for her work. You can reach Eni at www.oken3d.com.