Learning XNA 3.0

Chapter 9: 3D Game Development

Quiz Answers

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.

4. 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.

5. 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, while a translation * rotation will cause an object to orbit.

6. 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.

7. Fact or fiction: to map ...