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# Chapter 9: 3D Game Development

1. Does XNA use a right-handed or left-handed coordinate system?

XNA uses a right-handed coordinate system, which means that if you looked at the origin down the Z axis with positive X moving to your right, the Z axis would be positive in the direction coming toward you.

2. What makes up a viewing frustum (or field of view) for a camera in XNA 3D?

The viewing frustum is made up of a camera angle and near and far clipping planes.

3. What is culling?

Culling is the process of not drawing objects that are not facing the camera. For example, you never need to see the inside of a soccer ball when playing a soccer game in XNA, so the processor doesn’t draw that side of the object, which saves valuable processor time.

1. What is a vertex declaration?

A vertex declaration lets the graphics device know what type of data you are about to send so it knows how to process that data.

2. Fact or fiction: there is a difference between applying a rotation multiplied by a translation and applying a translation multiplied by a rotation.

Fact. A ```rotation * translation``` will cause an object to spin in place, whereas a ```translation * rotation``` will cause an object to orbit.

3. What order of translation and rotation would be needed in order to simulate a planet spinning in place while orbiting the origin?

To spin in place, you first need a rotation. Then to orbit, you need a translation and a rotation, in that order. So, the answer is `rotation *` ```translation *``` `rotation`.

4. Fact or fiction: to map ...

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