# Computer Graphics Questions & Answers – Three Dimensional Viewing

This set of Computer Graphics Multiple Choice Questions & Answers (MCQs) focuses on “Three Dimensional Viewing”.

1. Which of the following process is analogous to creating a view of a three dimensional scene?
a) Making a painting
b) Taking a photograph
c) Recording a sound
d) Editing a picture

Explanation: Taking a photograph is the most analogous to creating a view of a three dimensional scene because both of them involves similar steps to complete the process like viewing orientation, camera position and size of clipping window.

2. How many steps are involved in converting the world coordinates of a scene to device coordinates?
a) 2
b) 3
c) 5
d) 7

Explanation: A total of 5 steps are involved in converting the world coordinates of a scene to the device coordinates. These includes – Modelling Transformation, Viewing Transformation, Projection Transformation, Normalization Transformation and clipping and Viewport Transformation.

3. Which of the following step involves in placing the object into appropriate position within the scene using their world coordinates?
a) Modelling Transformation
b) Viewing Transformation
c) Projection Transformation
d) Viewport Transformation

Explanation: Modelling Transformation involves in placing the object into appropriate position within the scene using their world coordinates. In this step the shape of individual objects in a scene is constructed within the modelling coordinate and are placed into appropriate positions within the world coordinates.

4. Which of the following step involves converting viewing coordinates of a scene to the coordinate position on the projection plane?
a) Modelling Transformation
b) Viewing Transformation
c) Projection Transformation
d) Viewport Transformation

Explanation: Projection Transformation involves converting viewing coordinates of a scene to the coordinate position on the projection plane. This process involves mapping of the object point onto its image at the projection plane.

5. The Viewing plane or the projector is set up in which of the following position?
a) Perpendicular to x and aligned with y, z
b) Perpendicular to y and aligned with x, z
c) At origin
d) Perpendicular to z and aligned with x, y

Explanation: The viewing plane or the projector is set up in the direction perpendicular to z and aligned with x, y. These viewing coordinates describes a 3D object with respect to a viewer. The viewing plane also includes the view reference point which is the origin of the viewing plane.

6. Look vector points towards the direction in which the camera is looking.
a) True
b) False

Explanation: Look vector points towards the direction in which the camera is looking. It has three degrees of freedom and can be any vector in 3-space. Up vector is used to determine how the camera will be rotated around the look vector.

7. Which of the following formula is used for converting world coordinates to the viewing coordinates?
a) M WC, VC = R z x R y x R z x T
b) M WC, VC = R x ⋅ R y ⋅ R z ⋅T
c) M WC, VC = R z ⋅ R y ⋅ R z ⋅Tx . Ty. Tz
d) M WC, VC = R z ⋅ R y ⋅ R z ⋅T

Explanation: The formula that is used for converting world coordinates to the viewing coordinates is – M WC, VC = R x ⋅ R y ⋅ R z ⋅T
It is the dot product of the rotation vectors done in x, y and z direction as well as the translation vector that is used to convert the world coordinates to the viewing coordinates.

8. Which of the following is defined as mapping of a point P(x, y, z) onto its image P’(x’, y’, z’) in the projection plane?
a) Mapping
b) Transformation
c) Clipping
d) Projection

Explanation: Projection is defined as mapping of a point P(x, y, z) onto its image P’(x’, y’, z’) in the projection plane. Projection can be divided into two broad categories – parallel projection and perspective projection.

Sanfoundry Global Education & Learning Series – Computer Graphics.