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Book Excerpt: 3D Game Textures: Create Professional Game Art Using Photoshop
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Book Excerpt: 3D Game Textures: Create Professional Game Art Using Photoshop

June 22, 2006 Article Start Previous Page 2 of 6 Next

Light and Shadow

Of all the topics in traditional art, this is arguably the most important due to its difficulty to master and importance to the final work. Light and shadow give depth to and, as a result, define what we see. At its simplest, light and shadow are easy to see and understand. Most of us are familiar with shadow; our own shadow cast by the sun, making animal silhouettes with our hands on the wall, or a single light source shining on a sphere and the round shadow that it casts. That’s where this book will start. Light and shadow quickly get more complicated, and the examples in this book will get more complex as well. The book will start with the ability to see and analyze light and shadow in this chapter, move up to creating and tweaking light and shadow in Photoshop using Layer Styles for the most part, and finally look at some basic hand tweaking of light and shadow. If you desire to master the ability to hand paint light and shadow on complex and organic surfaces, then you are advised to take traditional art classes in illustration, sketching, and painting.

We all know that the absence of light is darkness, and in total darkness we can obviously see nothing at all, but the presence of too much light will also make it difficult to see. Too much light blows away shadow and removes depth and desaturates color. In the previous section we looked at how shape and form differ. We see that difference primarily as light and shadow as in the example of the circle and a sphere. But even if the sphere were lit evenly with no shadows and looked just like the circle, the difference would become apparent when rotated. The sphere would always look round if rotated, whereas once you began to rotate the circle it would begin to look like an oval until it eventually disappeared when completely sideways. In the previous example, where a shape was cut into an image of rusted metal and made to look like a metal space door using Photoshop Layer Effects, the highlights and shadows were faked using the various tools and their settings. In Figure 1-6 you can see the same door texture rotated from front to side. Notice the complete lack of depth in the image on the far right. The illusion is shattered.


Figure 1-6: Here is the same door texture from the previous section. Notice the complete lack of depth as we look at it from angles other than straight on. The illusion of depth is shattered.


Understanding light and shadow are very important in the process of creating quality textures. We will go into more depth on this topic as we work through this book. One of the main reasons for dwelling on the topic is not only due to the importance of light and shadow visually, but you will see that many of the decisions that need to be made are based on whether light and shadow should be represented using texture, geometry, or technology. To make this decision intelligently in a serious game production involves the input and expertise of many people. While what looks best is ideally the first priority, what runs best on the target computer is usually what the decision boils down to. So keep in mind that in game development you don’t want to make any assumptions about light and shadows--ask questions. I cover different scenarios of how light and shadow may be handled in a game in this book. It can be challenging to make shadows look good in any one of the situations. Too little and you lack depth, too much and the texture starts to look flat. Making shadows too long or intense is an easy mistake. And unless the game level specifically calls for that, on rare occasion, don’t do it. Technology sometimes handles the highlights and shadows. This is challenging because it is a new way of thinking that baffles many people who are not familiar with computer graphics. This method can also be a bit overwhelming because you go from creating one texture for a surface to creating three or more textures that all work together on one surface. Naming and storing those textures can get confusing if you let it get away from you.

Overall you want your textures to be as versatile as possible and that includes, to a great degree, the ability to use those textures under various lighting conditions. See Figure 1-7 for an example of a texture where the shadows and highlights have been improperly implemented and one that has been correctly created. For this reason we will purposely use highlight and shadow to a minimalist amount. You will find that if you need more depth in your texture than a modest amount of highlight and/or shadow, then you most likely need to create geometry or use a shader—or consider removing the source of shadow! If there is no need for a large electrical box on a wall, then don’t paint it in if it draws attention to itself and looks flat. If there is a need and you are creating deep and harsh shadows because of it, you may need to create the geometry for the protruding element. You may find that as game development technology accelerates, things like pipes, door knobs, and ledges are no longer painted into the texture but modeled in geometry. Many texture surface properties are no longer painted on. Reflections, specular highlights, bump mapping, and other aspects of highlight and shadow are now processed in real time.


Figure 1-7: The crate on the left has conflicting light sources. The shadow from edge of the crate is coming up from the bottom, is too dark, is too long, and even has a gap in it. The highlights on the edges are in conflict with the shadow cast on the inner panel of the crate, and they are too hot, or bright. The crate on the right has a more subtle, low-contrast, and diffuse highlight and shadow scheme and will work better in more diverse situations.


In the rest of this book we will take various approaches to light and shadow using both Photoshop’s Layer Effects to automate this process and other tools to hand paint highlights and shadows. One of the main benefits to creating your own highlights and shadows in your textures is that you can control them and make them more interesting as well as consistent. Nothing is worse than a texture with shadows from conflicting light sources: harsh, short shadows on some elements of the texture and longer, more diffuse shadows on others. See Figure 1-8 for an example of this. The human eye can detect these types of errors even if the human seeing it can’t quite understand why the image looks wrong. One of the artist’s greatest abilities is not only being able to create art, but also being able to consciously know and verbalize what he is seeing. In Figure 1-9 you can see the various types of shadows created as the light source changes. This is a simple demonstration. If you ever have the opportunity to light a 3D scene or movie set, you will discover that the range of variables for light and shadow can be quite large.


Figure 1-8: Here is a REALLY BAD texture created from two sources. Notice the difference in the shadows and highlights. The human eye can detect these errors even if the human seeing it can’t understand why the image looks wrong.


Figure 1-9: With one light source and a simple object you can see the range of shadows we can create. Each shadow tells us information about the object and the light source, such as location, intensity, etc.


Highlights also tell us a good bit about the light source as well as the object itself. In Figure 1-10 you can see another simple illustration of how different materials will have different highlight patterns and intensities. These materials lack any texture or color and simply show the highlights and shadows created on the surface by one consistent light source.

For a more advanced and in-depth discussion on the subject of light and shadow for 3D scenes, I recommend Essential CG Lighting Techniques by Darren Brooker.


Figure 1-10: With one light source and a simple object with various highlights on it, you can see that the object appears to be created of various materials. Keep in mind that what you are seeing is only highlight and shadow. How much does only this aspect of an image tell you about the material?

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