Learning XNA 3.0

Even More Rotations

So far, you've seen how to translate, rotate, and scale objects, but you've only rotated using a method called CreateRotationY, which rotates an object around the Y-axis.

There are other rotations that are worth noting here. You've probably guessed that as there's a CreateRotationY, there will also be CreateRotationX and CreateRotationZ methods. That's a pretty good guess, and as it turns out, you're right. These methods can be used to rotate an object around the Y-, X-, or Z-axis, respectively.

Another method used to apply rotations is Matrix.CreateFromYawPitchRoll. Essentially, this method allows you to create a rotation that combines rotations around the X-, Y-, and Z-axes simultaneously. As pictured in Figure 9-10, a yaw rotates an object around the Y-axis, a pitch rotates around the X-axis, and a roll rotates around the Z-axis.

Figure 9-10. Yaw, pitch, and roll

There's another method that should be mentioned here as well: Matrix.CreateFromAxisAngle. This method takes a parameter in the form of a Vector3 that represents an axis upon which to rotate an object (rather than specifying X, Y, or Z), as well as an angle at which to rotate the object. For example, imagine you're building a model of the solar system. You'll want to specify some arbitrary axis for the Earth to spin on, because the Earth's axis is tilted and doesn't line up exactly with X, Y, or Z.

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