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Learning XNA 3.0 by Aaron Reed

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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 ...

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