Game Development Reference
In-Depth Information
Understanding normal mapping
There is an interesting opportunity to add some extra details to your 3D model without
addinganyexcesstristoitsgeometry.Aregularobjectiswrappedbyaspecialtexture
that stores some relief information. It is like putting on a dress made of cloth with bul-
ging patterns. That is a very smart technical solution. A bitmap document keeps in-
formation about the heights of a specific region of an object. The data can be trans-
ferred and compressed as regular raster graphics. There is no need of special file
formats. Such a method is known as bump mapping because various elements of 3D
relief, called bumps for the sake of simplicity, are projected onto a flat image turning
into a map.
Classical bump maps are grayscale maps where heights are coded by a pixel's bright-
ness. A 3D engine wraps such a texture on an object but does not display it in a
straight form. It only uses it for simulation of extra geometry (generating both concave
and convex elements). All graphic details creating by a bump map are some sort of a
fake or technological trick, but the final results are pretty convincing and spectacular,
especially if the mapping is done perfectly.
Standard grayscale height mapping is pretty handy, but it has a drawback. Such maps
are not carefully optimized, and need some additional post-processing procedures
such as calculations of normals. That is why, now, a more popular form of mapping
is normal mapping. It uses the same paradigm. The height information is saved as
a raster document, but the data is stored in some pre-processing form that is more
natural for 3D calculations. Such a result is attained by converting X, Y, and Z coordin-
ates of the surface normals to RGB. Files with normal maps can be easily recognized
by a distinctive domination of blue color in their palette. This is because a projected
flat surface without any bumps is written as a single RGB color (128, 128, 255), which
is a shade of blue.
A racing game, Ice Driver, developed by Spooky House Studios UG (haftungsbeschränkt) uses nor-
mal mapping to create a shader effect of the bumped ice surface
