Happy with the bumpiness on your objects? If you look carefully I bet they’ll be a bit bland and when you compare the quality versus a normal map… well you’ll see. But wait, what is a normal map? Why would I want to use one, but isn’t a normal map just like a bump map?

Let’s start with the last statement, yes. Still scratching your head? Well, simply put normal maps and bump maps are cheats to cheaply (render time reference) mimic bumps in the surface without geometry. To gain the utmost realism, displacement maps are the way to go but we’ll save that for another discussion.

Let’s talk about what a normal map is. Now that we know that normal map and bump map are trying the achieve the same thing, they are different in the approach. Where a bump map uses a greyscale gradient to act as a height map (black=negative, grey=0, white=positive) a normal map is an RGB image that records the surface normals direction in x,y,z direction. XYZ? Greyscale? Indeed, it seems confusing but here’s the catch:

• bump maps are single axis movements taken from a height map being a greyscale image, which one could assume as being a linear scale.
• normal maps use 3 colours to describe surface movement in a relational XYZ direction relative to a coordinate system space of object space or tangent space.

There is a wealth of information out there but I want to provide a starting point for you to experiment with. I’ve provided some links to kick off further investigation, and also some solutions to implement normal maps. My suggestion is to try both bump maps and normal maps, but I think normal maps are more convincing and allow greater detail, which is why normal maps are popular in the gaming industry as they allow using low poly models to generate a high polygon model look without the geometry.

• nVidia has a nifty Photoshop plugin to generate normal maps using images. I find this useful in that you can convert your greyscale images into normal maps.
• CrazyBump is a very cool application to create a multiple set of maps from photographs
• A concise article on Normal Maps
• Wiki on Bump Mapping
• Wiki on Normal Mapping