Normal Mapping in Maya - Game Character Development with Maya - page 1000

Appendix A. Normal Mapping in Maya
A technique used in many of today's games is normal mapping. This is a method of making
a low-polygon object or character appear to have more surface detail than it actually has, by
collecting intricate lighting detail from a high-polygon version and applying it to the nor-
mals of the low one. Normals are the vectors (direction) a surface is facing.
Actuallyanapplicationofbumpmapping,normalmappingalsoworksfromabitmapimage.
Normalmapsaredifferentfrombumpmaps,however,intermsoftheinformationtheystore.
Bump maps work off a grayscale image that only registers changes in height; a normal map
uses an RGB image, which contains enough information to store not only height but direc-
tion as well.
Red is the direction across the object, from left to right. Green goes from top to bottom, and
the amount of blue dictates the height. The stronger the color, the more that normal faces in
that specific direction.
Normal maps are becoming a key part of game development, so it's important to have some
experience with creating them in Maya.
System Requirements
To generate a normal map, you have to be running Maya 6 or later. This version has all the
appropriate tools that allow you to generate and apply normal maps.
There'saplug-inavailableforpreviousversionsofMaya,calledRayDisplace,thatwillgen-
erate normal map data within Maya, but it's a bit unstable. There are also stand-alone utilit-
ies from the major card manufacturers that process the high-polygon model data to produce
thenormalmapdata.ButMaya6isthefirstin-softwareimplementationofnormalmapping.
In addition, your video card must be able to support normal maps. Maya will generate the
dataregardlessofyourgraphicscard'sabilities,butwithoutthepropervideocard,youwon't
be able to use Maya's High Quality Interactive Render option to view the maps.
Generating a Normal Map
First you need to get Maya set up for generating normal maps.
Go to Window > Settings/Preferences > Plug-in Manager. You will see the Plug-in Manager
shown in Figure A.1 . This is where you control the plug-ins that are loaded into memory.
Work your way down the list until you reach the plug-in called TransferSurfaceInfo.mll.