CHAPTER 2 ■ SETTING UP DIFFERENT CAMERA MODES IN YOUR 3D WORLD
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perpendicular to your index finger and thumb. Now, imagine your three fingers are the axis of
yourcoordinatesystem.IfyouhaveanRHcoordinatesystem,theremustbeawayyoumap
the x-axis of your coordinate system on your thumb, your y-axis on your index finger, and your
z-axis on your middle finger.
Fortheaxesdescribedinthefirstparagraphhere,thiscorrespondstoyourthumbpoint-
ing to the right and your middle finger up (no offense intended). To represent the “official”
XNA coordinate system, hold your thumb to the right (positive x-axis = right) and your index
finger up (positive y-axis = up). Now, you see that your middle finger points backward (posi-
tivez-axis=backward),sothat’swhy ...