How to Create a 3D Bump Map Using Photoshop

3D bump map

Bump maps are texture maps used in 3D modeling to artificially create textured surfaces without having to model the individual details. Trying to model detailed textures can create a mess of thousands of extra polygons, multiplying the time to model them, while yielding unrealistic-looking models and exploding the rendering time and processing power they require. Without realistic 3D textures, though, 3D models appear flat and lifeless.

Bump maps are an answer. They're layered under full-color painted texture maps and use grayscale to instruct 3D modeling programs on how far to extrude polygonal surfaces. Black represents the highest extreme of extrusion, white represents the flattest areas, and shades of gray cover everything in between.

For example, if you were texturing a lizard's skin, a bump map for the skin could use a mid-level gray as a baseline for the skin surface, with white for the deepest cracks and darker gray spots for the raised, pebbled areas, all of this without modeling a single bump or crack. You can even use a bump map to make facial highlights and shadows seem more realistic or add details such as folds and wrinkles to a model's clothing or armor.

It's an easy way to add lots of detail without adding lots of work and resource overhead. Rather than having to manually choose every little bump on your model, a bump map automates the process. It tells the 3D program to change the polygons in relation to your bump map procedurally, which reduces the load on computer resources when it renders the model.

Making Your Own Bump Maps

Creating a bump map in Photoshop is easy, especially if you already have a texture map with highlights and shadows painted in color.

  1. Either open your existing colored texture map or create one in Photoshop using paint tools. If you're just looking for a generic texture and not something specific like facial shading, you can use layer styles such as the Pattern Overlay to generate a repeating texture. For specifically painted detail, you'll need the exact map to make sure that the color-painted highlights and shadows line up with the bump map's texture extrusions.
  2. Save a grayscale copy of the map by using the Desaturate function under the Image > Adjustments menu. If you've generated your texture using layer styles and pattern overlays, you may need to flatten the layer so that your adjustments affect the texture and not just the base color underneath.
  3. Depending on the type of shading you've done, you may need to invert the image. In the original color version, you'd have painted shadows dark and more elevated areas brighter and more exposed to the lighting and tone in the shading. In the bump map, though, the lighter areas are interpreted as flatter while darker areas are interpreted as higher, so leaving it as is would create raised shadows and sunken highlights—the opposite of what you're going for. You can find the Invert function in the same place you found the Desaturate function, under the Image > Adjustments menu.
  1. You may need to tweak the bump map to increase the contrast between lighter and darker areas. Using it as is may not create the depth of detail that you're looking for in your texture. You can use the Brightness and Contrast tool under the Image > Adjustments menu to sharpen the image and increase the contrast.
  2. Save the file, preferably in a lossless format with a high level of detail, like BMP / bitmap, though you'll need to check your 3D program for image format compatibility.

Once you've created your bump map, all you need to do is import it into your 3D animation program. Different programs have different ways of integrating bump maps into a model or polygon surface, but the controls for the bump map should allow you to define a range to make sure the raised textures and depressions don't extrude to extremes or scale down so small that they hardly show.